Merge pull request #29402 from mavasani/ForEachToLinqMethod

Add refactoring to convert foreach loop into linq invocations (Select…

src/Features/CSharp/Portable/ConvertLinq/ConvertForEachToLinqQuery/AbstractConverter.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
@@ -22,7 +23,27 @@ public AbstractConverter(ForEachInfo<ForEachStatementSyntax, StatementSyntax> fo
         {
             ForEachInfo = forEachInfo;
         }
-        public abstract void Convert(SyntaxEditor editor, CancellationToken cancellationToken);
+
+        public abstract void Convert(SyntaxEditor editor, bool convertToQuery, CancellationToken cancellationToken);
+
+        /// <summary>
+        /// Creates a query expression or a linq invocation expression.
+        /// </summary>
+        /// <param name="selectExpression">expression to be used into the last Select in the query expression or linq invocation.</param>
+        /// <param name="leadingTokensForSelect">extra leading tokens to be added to the select clause</param>
+        /// <param name="trailingTokensForSelect">extra trailing tokens to be added to the select clause</param>
+        /// <param name="convertToQuery">Flag indicating if a query expression should be generated</param>
+        /// <returns></returns>
+        protected ExpressionSyntax CreateQueryExpressionOrLinqInvocation(
+            ExpressionSyntax selectExpression,
+            IEnumerable<SyntaxToken> leadingTokensForSelect,
+            IEnumerable<SyntaxToken> trailingTokensForSelect,
+            bool convertToQuery)
+        {
+            return convertToQuery
+                ? CreateQueryExpression(selectExpression, leadingTokensForSelect, trailingTokensForSelect)
+                : (ExpressionSyntax)CreateLinqInvocation(selectExpression, leadingTokensForSelect, trailingTokensForSelect);
+        }
 
         /// <summary>
         /// Creates a query expression.
@@ -31,7 +52,7 @@ public AbstractConverter(ForEachInfo<ForEachStatementSyntax, StatementSyntax> fo
         /// <param name="leadingTokensForSelect">extra leading tokens to be added to the select clause</param>
         /// <param name="trailingTokensForSelect">extra trailing tokens to be added to the select clause</param>
         /// <returns></returns>
-        protected QueryExpressionSyntax CreateQueryExpression(
+        private QueryExpressionSyntax CreateQueryExpression(
             ExpressionSyntax selectExpression,
             IEnumerable<SyntaxToken> leadingTokensForSelect,
             IEnumerable<SyntaxToken> trailingTokensForSelect)
@@ -73,8 +94,8 @@ private static QueryClauseSyntax CreateQueryClause(ExtendedSyntaxNode node)
         }
 
         private static FromClauseSyntax CreateFromClause(
-            ForEachStatementSyntax forEachStatement, 
-            IEnumerable<SyntaxTrivia> extraLeadingTrivia, 
+            ForEachStatementSyntax forEachStatement,
+            IEnumerable<SyntaxTrivia> extraLeadingTrivia,
             IEnumerable<SyntaxTrivia> extraTrailingTrivia)
             => SyntaxFactory.FromClause(
                     fromKeyword: SyntaxFactory.Token(SyntaxKind.FromKeyword)
@@ -93,5 +114,166 @@ private static QueryClauseSyntax CreateQueryClause(ExtendedSyntaxNode node)
                     expression: forEachStatement.Expression)
                         .WithCommentsFrom(extraLeadingTrivia, extraTrailingTrivia, forEachStatement.CloseParenToken);
 
+        /// <summary>
+        /// Creates a linq invocation expression.
+        /// </summary>
+        /// <param name="selectExpression">expression to be used in the last 'Select' invocation</param>
+        /// <param name="leadingTokensForSelect">extra leading tokens to be added to the select clause</param>
+        /// <param name="trailingTokensForSelect">extra trailing tokens to be added to the select clause</param>
+        /// <returns></returns>
+        private InvocationExpressionSyntax CreateLinqInvocation(
+            ExpressionSyntax selectExpression,
+            IEnumerable<SyntaxToken> leadingTokensForSelect,
+            IEnumerable<SyntaxToken> trailingTokensForSelect)
+        {
+            var foreachStatement = ForEachInfo.ForEachStatement;
+            selectExpression = selectExpression.WithCommentsFrom(leadingTokensForSelect, ForEachInfo.TrailingTokens.Concat(trailingTokensForSelect));
+            var currentExtendedNodeIndex = 0;
+
+            return CreateLinqInvocation(
+                foreachStatement,
+                receiverForInvocation: foreachStatement.Expression,
+                selectExpression: selectExpression,
+                leadingCommentsTrivia: ForEachInfo.LeadingTokens.GetTrivia(),
+                trailingCommentsTrivia: Enumerable.Empty<SyntaxTrivia>(),
+                currentExtendedNodeIndex: ref currentExtendedNodeIndex)
+                .WithAdditionalAnnotations(Formatter.Annotation);
+        }
+
+        private InvocationExpressionSyntax CreateLinqInvocation(
+            ForEachStatementSyntax forEachStatement,
+            ExpressionSyntax receiverForInvocation,
+            IEnumerable<SyntaxTrivia> leadingCommentsTrivia,
+            IEnumerable<SyntaxTrivia> trailingCommentsTrivia,
+            ExpressionSyntax selectExpression,
+            ref int currentExtendedNodeIndex)
+        {
+            leadingCommentsTrivia = forEachStatement.ForEachKeyword.GetAllTrivia().Concat(leadingCommentsTrivia);
+
+            // Recursively create linq invocations, possibly updating the receiver (Where invocations), to get the inner expression for
+            // the lambda body for the linq invocation to be created for this foreach statement. For example:
+            //
+            // INPUT:
+            //   foreach (var n1 in c1)
+            //      foreach (var n2 in c2)
+            //          if (n1 > n2)
+            //              yield return n1 + n2;
+            //
+            // OUTPUT:
+            //   c1.SelectMany(n1 => c2.Where(n2 => n1 > n2).Select(n2 => n1 + n2))
+            //
+            var hasForEachChild = false;
+            var lambdaBody = CreateLinqInvocationForExtendedNode(selectExpression, ref currentExtendedNodeIndex, ref receiverForInvocation, ref hasForEachChild);
+            var lambda = SyntaxFactory.SimpleLambdaExpression(
+                SyntaxFactory.Parameter(
+                    forEachStatement.Identifier.WithPrependedLeadingTrivia(
+                    SyntaxNodeOrTokenExtensions.GetTrivia(forEachStatement.Type.GetFirstToken())
+                        .FilterComments(addElasticMarker: false))),
+                lambdaBody)
+                .WithCommentsFrom(leadingCommentsTrivia, trailingCommentsTrivia,
+                    forEachStatement.OpenParenToken, forEachStatement.InKeyword, forEachStatement.CloseParenToken);
+
+            // Create Select or SelectMany linq invocation for this foreach statement. For example:
+            //
+            // INPUT:
+            //   foreach (var n1 in c1)
+            //      ...
+            //
+            // OUTPUT:
+            //   c1.Select(n1 => ...
+            //      OR
+            //   c1.SelectMany(n1 => ...
+            //
+            var invokedMethodName = !hasForEachChild ? nameof(Enumerable.Select) : nameof(Enumerable.SelectMany);
+            return SyntaxFactory.InvocationExpression(
+                SyntaxFactory.MemberAccessExpression(
+                    SyntaxKind.SimpleMemberAccessExpression,
+                    receiverForInvocation.Parenthesize(),
+                    SyntaxFactory.IdentifierName(invokedMethodName)),
+                SyntaxFactory.ArgumentList(SyntaxFactory.SingletonSeparatedList(
+                    SyntaxFactory.Argument(lambda))));
+        }
+
+        /// <summary>
+        /// Creates a linq invocation expression for the <see cref="ForEachInfo{ForEachStatementSyntax, StatementSyntax}.ConvertingExtendedNodes"/> node at the given index <paramref name="extendedNodeIndex"/>
+        /// or returns the <paramref name="selectExpression"/> if all extended nodes have been processed.
+        /// </summary>
+        /// <param name="selectExpression">Innermost select expression</param>
+        /// <param name="extendedNodeIndex">Index into <see cref="ForEachInfo{ForEachStatementSyntax, StatementSyntax}.ConvertingExtendedNodes"/> to be processed and updated.</param>
+        /// <param name="receiver">Receiver for the generated linq invocation. Updated when processing an if statement.</param>
+        /// <param name="hasForEachChild">Flag indicating if any of the processed <see cref="ForEachInfo{ForEachStatementSyntax, StatementSyntax}.ConvertingExtendedNodes"/> is a <see cref="ForEachStatementSyntax"/>.</param>
+        private ExpressionSyntax CreateLinqInvocationForExtendedNode(
+            ExpressionSyntax selectExpression,
+            ref int extendedNodeIndex,
+            ref ExpressionSyntax receiver,
+            ref bool hasForEachChild)
+        {
+            // Check if we have converted all the descendant foreach/if statements.
+            // If so, we return the select expression.
+            if (extendedNodeIndex == ForEachInfo.ConvertingExtendedNodes.Length)
+            {
+                return selectExpression;
+            }
+
+            // Otherwise, convert the next foreach/if statement into a linq invocation.
+            var node = ForEachInfo.ConvertingExtendedNodes[extendedNodeIndex];
+            switch (node.Node.Kind())
+            {
+                // Nested ForEach statement is converted into a nested Select or SelectMany linq invocation. For example:
+                //
+                // INPUT:
+                //   foreach (var n1 in c1)
+                //      foreach (var n2 in c2)
+                //          ...
+                //
+                // OUTPUT:
+                //   c1.SelectMany(n1 => c2.Select(n2 => ...
+                //
+                case SyntaxKind.ForEachStatement:
+                    hasForEachChild = true;
+                    var foreachStatement = (ForEachStatementSyntax)node.Node;
+                    ++extendedNodeIndex;
+                    return CreateLinqInvocation(
+                        foreachStatement,
+                        receiverForInvocation: foreachStatement.Expression,
+                        selectExpression: selectExpression,
+                        leadingCommentsTrivia: node.ExtraLeadingComments,
+                        trailingCommentsTrivia: node.ExtraTrailingComments,
+                        currentExtendedNodeIndex: ref extendedNodeIndex);
+
+                // Nested If statement is converted into a Where method invocation on the current receiver. For example:
+                //
+                // INPUT:
+                //   foreach (var n1 in c1)
+                //      if (n1 > 0)
+                //          ...
+                //
+                // OUTPUT:
+                //   c1.Where(n1 => n1 > 0).Select(n1 => ...
+                //
+                case SyntaxKind.IfStatement:
+                    var ifStatement = (IfStatementSyntax)node.Node;
+                    var parentForEachStatement = ifStatement.GetAncestor<ForEachStatementSyntax>();
+                    var lambdaParameter = SyntaxFactory.Parameter(SyntaxFactory.Identifier(parentForEachStatement.Identifier.ValueText));
+                    var lambda = SyntaxFactory.SimpleLambdaExpression(
+                        SyntaxFactory.Parameter(
+                            SyntaxFactory.Identifier(parentForEachStatement.Identifier.ValueText)),
+                        ifStatement.Condition.WithCommentsFrom(ifStatement.OpenParenToken, ifStatement.CloseParenToken))
+                        .WithCommentsFrom(ifStatement.IfKeyword.GetAllTrivia().Concat(node.ExtraLeadingComments), node.ExtraTrailingComments);
+
+                    receiver = SyntaxFactory.InvocationExpression(
+                        SyntaxFactory.MemberAccessExpression(
+                            SyntaxKind.SimpleMemberAccessExpression,
+                            receiver.Parenthesize(),
+                            SyntaxFactory.IdentifierName(nameof(Enumerable.Where))),
+                        SyntaxFactory.ArgumentList(SyntaxFactory.SingletonSeparatedList(
+                            SyntaxFactory.Argument(lambda))));
+
+                    ++extendedNodeIndex;
+                    return CreateLinqInvocationForExtendedNode(selectExpression, ref extendedNodeIndex, ref receiver, ref hasForEachChild);
+            }
+
+            throw ExceptionUtilities.Unreachable;
+        }
     }
 }

src/Features/CSharp/Portable/ConvertLinq/ConvertForEachToLinqQuery/AbstractToMethodConverter.cs

@@ -45,12 +45,12 @@ internal abstract class AbstractToMethodConverter : AbstractConverter
 
         protected abstract bool CanReplaceInitialization(ExpressionSyntax expressionSyntax, CancellationToken cancellationToken);
 
-        protected abstract StatementSyntax CreateDefaultStatement(QueryExpressionSyntax queryExpression, ExpressionSyntax expression);
+        protected abstract StatementSyntax CreateDefaultStatement(ExpressionSyntax queryOrLinqInvocationExpression, ExpressionSyntax expression);
 
-        public override void Convert(SyntaxEditor editor, CancellationToken cancellationToken)
+        public override void Convert(SyntaxEditor editor, bool convertToQuery, CancellationToken cancellationToken)
         {
-            var queryExpression = CreateQueryExpression(
-                _selectExpression, Enumerable.Empty<SyntaxToken>(), Enumerable.Empty<SyntaxToken>());
+            var queryOrLinqInvocationExpression = CreateQueryExpressionOrLinqInvocation(
+                _selectExpression, Enumerable.Empty<SyntaxToken>(), Enumerable.Empty<SyntaxToken>(), convertToQuery);
 
             var previous = ForEachInfo.ForEachStatement.GetPreviousStatement();
 
@@ -98,7 +98,7 @@ public override void Convert(SyntaxEditor editor, CancellationToken cancellation
             // list.AddRange(query) or counter += query.Count();
             editor.ReplaceNode(
                 ForEachInfo.ForEachStatement,
-                CreateDefaultStatement(queryExpression, _modifyingExpression).WithAdditionalAnnotations(Formatter.Annotation));
+                CreateDefaultStatement(queryOrLinqInvocationExpression, _modifyingExpression).WithAdditionalAnnotations(Formatter.Annotation));
 
             return;
 
@@ -138,7 +138,7 @@ void Convert(ExpressionSyntax replacingExpression, SyntaxNode nodeToRemoveIfFoll
 
                 editor.ReplaceNode(
                     replacingExpression,
-                    CreateInvocationExpression(queryExpression)
+                    CreateInvocationExpression(queryOrLinqInvocationExpression)
                         .WithCommentsFrom(leadingTrivia, _trivia).KeepCommentsAndAddElasticMarkers());
                 editor.RemoveNode(ForEachInfo.ForEachStatement);
             }
@@ -182,11 +182,11 @@ SyntaxTrivia[] GetTriviaFromNode(SyntaxNode node)
 
         // query => query.Method()
         // like query.Count() or query.ToList()
-        protected InvocationExpressionSyntax CreateInvocationExpression(QueryExpressionSyntax queryExpression)
+        protected InvocationExpressionSyntax CreateInvocationExpression(ExpressionSyntax queryOrLinqInvocationExpression)
             => SyntaxFactory.InvocationExpression(
                     SyntaxFactory.MemberAccessExpression(
                         SyntaxKind.SimpleMemberAccessExpression,
-                        SyntaxFactory.ParenthesizedExpression(queryExpression),
+                        SyntaxFactory.ParenthesizedExpression(queryOrLinqInvocationExpression),
                         SyntaxFactory.IdentifierName(MethodName))).WithAdditionalAnnotations(Formatter.Annotation);
     }
 }

src/Features/CSharp/Portable/ConvertLinq/ConvertForEachToLinqQuery/CSharpConvertForEachToLinqQueryProvider.cs

@@ -27,7 +27,8 @@ internal sealed class CSharpConvertForEachToLinqQueryProvider
 
         protected override ForEachInfo<ForEachStatementSyntax, StatementSyntax> CreateForEachInfo(
             ForEachStatementSyntax forEachStatement,
-            SemanticModel semanticModel)
+            SemanticModel semanticModel,
+            bool convertLocalDeclarations)
         {
             var identifiersBuilder = ArrayBuilder<SyntaxToken>.GetInstance();
             identifiersBuilder.Add(forEachStatement.Identifier);
@@ -161,6 +162,11 @@ internal sealed class CSharpConvertForEachToLinqQueryProvider
             // Try to prepare variable declarations to be converted into separate let clauses.
             bool TryProcessLocalDeclarationStatement(LocalDeclarationStatementSyntax localDeclarationStatement)
             {
+                if (!convertLocalDeclarations)
+                {
+                    return false;
+                }
+
                 // Do not support declarations without initialization.
                 // int a = 0, b, c = 0;
                 if (localDeclarationStatement.Declaration.Variables.All(variable => variable.Initializer != null))

src/Features/CSharp/Portable/ConvertLinq/ConvertForEachToLinqQuery/DefaultConverter.cs

@@ -20,7 +20,7 @@ public DefaultConverter(ForEachInfo<ForEachStatementSyntax, StatementSyntax> for
         {
         }
 
-        public override void Convert(SyntaxEditor editor, CancellationToken cancellationToken)
+        public override void Convert(SyntaxEditor editor, bool convertToQuery, CancellationToken cancellationToken)
         {
             // Filter out identifiers which are not used in statements.
             var variableNamesReadInside = new HashSet<string>(ForEachInfo.Statements
@@ -35,14 +35,15 @@ public override void Convert(SyntaxEditor editor, CancellationToken cancellation
 
             editor.ReplaceNode(
                 ForEachInfo.ForEachStatement,
-                CreateDefaultReplacementStatement(ForEachInfo, identifiersUsedInStatements, block)
+                CreateDefaultReplacementStatement(ForEachInfo, identifiersUsedInStatements, block, convertToQuery)
                     .WithAdditionalAnnotations(Formatter.Annotation));
         }
 
         private StatementSyntax CreateDefaultReplacementStatement(
             ForEachInfo<ForEachStatementSyntax, StatementSyntax> forEachInfo,
             IEnumerable<SyntaxToken> identifiers,
-            BlockSyntax block)
+            BlockSyntax block,
+            bool convertToQuery)
         {
             var identifiersCount = identifiers.Count();
             if (identifiersCount == 0)
@@ -51,10 +52,11 @@ public override void Convert(SyntaxEditor editor, CancellationToken cancellation
                 return SyntaxFactory.ForEachStatement(
                     VarNameIdentifier,
                     SyntaxFactory.Identifier("_"),
-                    CreateQueryExpression(
+                    CreateQueryExpressionOrLinqInvocation(
                         SyntaxFactory.AnonymousObjectCreationExpression(),
                         Enumerable.Empty<SyntaxToken>(),
-                        Enumerable.Empty<SyntaxToken>()),
+                        Enumerable.Empty<SyntaxToken>(),
+                        convertToQuery),
                     block);
             }
             else if (identifiersCount == 1)
@@ -63,10 +65,11 @@ public override void Convert(SyntaxEditor editor, CancellationToken cancellation
                 return SyntaxFactory.ForEachStatement(
                     VarNameIdentifier,
                     identifiers.Single(),
-                    CreateQueryExpression(
+                    CreateQueryExpressionOrLinqInvocation(
                         SyntaxFactory.IdentifierName(identifiers.Single()),
                         Enumerable.Empty<SyntaxToken>(),
-                        Enumerable.Empty<SyntaxToken>()),
+                        Enumerable.Empty<SyntaxToken>(),
+                        convertToQuery),
                     block);
             }
             else
@@ -83,10 +86,11 @@ public override void Convert(SyntaxEditor editor, CancellationToken cancellation
                 // Generate foreach(var (a,b) ... select (a, b))
                 return SyntaxFactory.ForEachVariableStatement(
                     declaration, 
-                    CreateQueryExpression(
+                    CreateQueryExpressionOrLinqInvocation(
                         tupleForSelectExpression, 
                         Enumerable.Empty<SyntaxToken>(), 
-                        Enumerable.Empty<SyntaxToken>()), 
+                        Enumerable.Empty<SyntaxToken>(),
+                        convertToQuery), 
                     block);
             }
         }

src/Features/CSharp/Portable/ConvertLinq/ConvertForEachToLinqQuery/ToCountConverter.cs

@@ -39,11 +39,11 @@ internal sealed class ToCountConverter : AbstractToMethodConverter
         ///  
         ///  Output:
         ///  counter += queryGenerated.Count();
-        protected override StatementSyntax CreateDefaultStatement(QueryExpressionSyntax queryExpression, ExpressionSyntax expression)
+        protected override StatementSyntax CreateDefaultStatement(ExpressionSyntax queryOrLinqInvocationExpression, ExpressionSyntax expression)
             => SyntaxFactory.ExpressionStatement(
                 SyntaxFactory.AssignmentExpression(
                     SyntaxKind.AddAssignmentExpression,
                     expression,
-                    CreateInvocationExpression(queryExpression)));
+                    CreateInvocationExpression(queryOrLinqInvocationExpression)));
     }
 }

src/Features/CSharp/Portable/ConvertLinq/ConvertForEachToLinqQuery/ToToListConverter.cs

@@ -44,13 +44,13 @@ internal sealed class ToToListConverter : AbstractToMethodConverter
         ///  
         ///  Output:
         ///  list.AddRange(queryGenerated);
-        protected override StatementSyntax CreateDefaultStatement(QueryExpressionSyntax queryExpression, ExpressionSyntax expression)
+        protected override StatementSyntax CreateDefaultStatement(ExpressionSyntax queryOrLinqInvocationExpression, ExpressionSyntax expression)
             => SyntaxFactory.ExpressionStatement(
                 SyntaxFactory.InvocationExpression(
                     SyntaxFactory.MemberAccessExpression(
                         SyntaxKind.SimpleMemberAccessExpression,
                         expression,
                         SyntaxFactory.IdentifierName(nameof(List<object>.AddRange))),
-                    SyntaxFactory.ArgumentList(SyntaxFactory.SingletonSeparatedList(SyntaxFactory.Argument(queryExpression)))));
+                    SyntaxFactory.ArgumentList(SyntaxFactory.SingletonSeparatedList(SyntaxFactory.Argument(queryOrLinqInvocationExpression)))));
     }
 }

src/Features/CSharp/Portable/ConvertLinq/ConvertForEachToLinqQuery/YieldReturnConverter.cs

@@ -23,9 +23,9 @@ internal sealed class YieldReturnConverter : AbstractConverter
             _yieldBreakStatement = yieldBreakStatement;
         }
 
-        public override void Convert(SyntaxEditor editor, CancellationToken cancellationToken)
+        public override void Convert(SyntaxEditor editor, bool convertToQuery, CancellationToken cancellationToken)
         {
-            var queryExpression = CreateQueryExpression(
+            var queryOrLinqInvocationExpression = CreateQueryExpressionOrLinqInvocation(
                selectExpression: _yieldReturnStatement.Expression,
                leadingTokensForSelect: new[] { _yieldReturnStatement.YieldKeyword, _yieldReturnStatement.ReturnOrBreakKeyword },
                trailingTokensForSelect: _yieldBreakStatement != null
@@ -33,11 +33,12 @@ public override void Convert(SyntaxEditor editor, CancellationToken cancellation
                                                 _yieldBreakStatement.YieldKeyword,
                                                 _yieldBreakStatement.ReturnOrBreakKeyword,
                                                 _yieldBreakStatement.SemicolonToken }
-                                        : new[] { _yieldReturnStatement.SemicolonToken });
+                                        : new[] { _yieldReturnStatement.SemicolonToken },
+               convertToQuery: convertToQuery);
 
             editor.ReplaceNode(
                 ForEachInfo.ForEachStatement, 
-                SyntaxFactory.ReturnStatement(queryExpression).WithAdditionalAnnotations(Formatter.Annotation));
+                SyntaxFactory.ReturnStatement(queryOrLinqInvocationExpression).WithAdditionalAnnotations(Formatter.Annotation));
 
             // Delete the yield break just after the loop.
             if (_yieldBreakStatement != null)

src/Features/Core/Portable/ConvertLinq/ConvertForEachToLinqQuery/AbstractConvertForEachToLinqQueryProvider.cs

@@ -25,7 +25,7 @@ internal abstract class AbstractConvertForEachToLinqQueryProvider<TForEachStatem
         /// 4) trailing comments to be added to the end
         /// </returns>
         protected abstract ForEachInfo<TForEachStatement, TStatement> CreateForEachInfo(
-            TForEachStatement forEachStatement, SemanticModel semanticModel);
+            TForEachStatement forEachStatement, SemanticModel semanticModel, bool convertLocalDeclarations);
 
         /// <summary>
         /// Tries to build a specific converter that covers e.g. Count, ToList, yield return or other similar cases.
@@ -84,7 +84,7 @@ public override async Task ComputeRefactoringsAsync(CodeRefactoringContext conte
 
             var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
-            if (!TryBuildConverter(forEachStatement, semanticModel, cancellationToken, out var converter))
+            if (!TryBuildConverter(forEachStatement, semanticModel, convertLocalDeclarations: true, cancellationToken, out var queryConverter))
             {
                 return;
             }
@@ -95,19 +95,56 @@ public override async Task ComputeRefactoringsAsync(CodeRefactoringContext conte
                 return;
             }
 
+            // Offer refactoring to convert foreach to LINQ query expression. For example:
+            //
+            // INPUT:
+            //  foreach (var n1 in c1)
+            //      foreach (var n2 in c2)
+            //          if (n1 > n2)
+            //              yield return n1 + n2;
+            //
+            // OUTPUT:
+            //  from n1 in c1
+            //  from n2 in c2
+            //  where n1 > n2
+            //  select n1 + n2
+            //
             context.RegisterRefactoring(
                 new ForEachToLinqQueryCodeAction(
-                    FeaturesResources.Convert_to_query, 
-                    c => ApplyConversion(converter, document, c)));
+                    FeaturesResources.Convert_to_linq, 
+                    c => ApplyConversion(queryConverter, document, convertToQuery: true, c)));
+
+            // Offer refactoring to convert foreach to LINQ invocation expression. For example:
+            //
+            // INPUT:
+            //   foreach (var n1 in c1)
+            //      foreach (var n2 in c2)
+            //          if (n1 > n2)
+            //              yield return n1 + n2;
+            //
+            // OUTPUT:
+            //   c1.SelectMany(n1 => c2.Where(n2 => n1 > n2).Select(n2 => n1 + n2))
+            //
+            // CONSIDER: Currently, we do not handle foreach statements with a local declaration statement for Convert_to_linq refactoring,
+            //           though we do handle them for the Convert_to_query refactoring above.
+            //           In future, we can consider supporting them by creating anonymous objects/tuples wrapping the local declarations.
+            if (TryBuildConverter(forEachStatement, semanticModel, convertLocalDeclarations: false, cancellationToken, out var linqConverter))
+            {
+                context.RegisterRefactoring(
+                    new ForEachToLinqQueryCodeAction(
+                        FeaturesResources.Convert_to_linq_call_form,
+                        c => ApplyConversion(linqConverter, document, convertToQuery: false, c)));
+            }
         }
 
         private Task<Document> ApplyConversion(
-            IConverter<TForEachStatement, TStatement> converter, 
-            Document document, 
+            IConverter<TForEachStatement, TStatement> converter,
+            Document document,
+            bool convertToQuery,
             CancellationToken cancellationToken)
         {
             var editor = new SyntaxEditor(converter.ForEachInfo.SemanticModel.SyntaxTree.GetRoot(cancellationToken), document.Project.Solution.Workspace);
-            converter.Convert(editor, cancellationToken);
+            converter.Convert(editor, convertToQuery, cancellationToken);
             var newRoot = editor.GetChangedRoot();
             var rootWithLinqUsing = AddLinqUsing(converter, converter.ForEachInfo.SemanticModel, newRoot);
             return Task.FromResult(document.WithSyntaxRoot(rootWithLinqUsing));
@@ -119,10 +156,11 @@ public override async Task ComputeRefactoringsAsync(CodeRefactoringContext conte
         private bool TryBuildConverter(
             TForEachStatement forEachStatement,
             SemanticModel semanticModel,
+            bool convertLocalDeclarations,
             CancellationToken cancellationToken,
             out IConverter<TForEachStatement, TStatement> converter)
         {
-            var forEachInfo = CreateForEachInfo(forEachStatement, semanticModel);
+            var forEachInfo = CreateForEachInfo(forEachStatement, semanticModel, convertLocalDeclarations);
 
             if (forEachInfo.Statements.Length == 1 &&
                 TryBuildSpecificConverter(forEachInfo, semanticModel, forEachInfo.Statements.Single(), cancellationToken, out converter))

src/Features/Core/Portable/ConvertLinq/ConvertForEachToLinqQuery/IConverter.cs

@@ -9,6 +9,6 @@ internal interface IConverter<TForEachStatement, TStatement>
     {
         ForEachInfo<TForEachStatement, TStatement> ForEachInfo { get; }
 
-        void Convert(SyntaxEditor editor, CancellationToken cancellationToken);
+        void Convert(SyntaxEditor editor, bool convertToQuery, CancellationToken cancellationToken);
     }
 }

src/Features/Core/Portable/FeaturesResources.Designer.cs

@@ -934,14 +934,23 @@ internal class FeaturesResources {
         }
         
         /// <summary>
-        ///   Looks up a localized string similar to Convert to query.
+        ///   Looks up a localized string similar to Convert to LINQ.
         /// </summary>
-        internal static string Convert_to_query {
+        internal static string Convert_to_linq {
             get {
-                return ResourceManager.GetString("Convert_to_query", resourceCulture);
+                return ResourceManager.GetString("Convert_to_linq", resourceCulture);
             }
         }
-
+        
+        /// <summary>
+        ///   Looks up a localized string similar to Convert to LINQ (call form).
+        /// </summary>
+        internal static string Convert_to_linq_call_form {
+            get {
+                return ResourceManager.GetString("Convert_to_linq_call_form", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Convert to struct.
         /// </summary>

src/Features/Core/Portable/FeaturesResources.resx

@@ -1376,8 +1376,8 @@ This version used in: {2}</value>
   <data name="Convert_to_conditional_expression" xml:space="preserve">
     <value>Convert to conditional expression</value>
   </data>
-  <data name="Convert_to_query" xml:space="preserve">
-    <value>Convert to query</value>
+  <data name="Convert_to_linq" xml:space="preserve">
+    <value>Convert to LINQ</value>
   </data>
   <data name="Convert_to_tuple" xml:space="preserve">
     <value>Convert to tuple</value>
@@ -1403,4 +1403,7 @@ This version used in: {2}</value>
   <data name="Formatting_document" xml:space="preserve">
     <value>Formatting document</value>
   </data>
+  <data name="Convert_to_linq_call_form" xml:space="preserve">
+    <value>Convert to LINQ (call form)</value>
+  </data>
 </root>
\ No newline at end of file

src/Features/Core/Portable/xlf/FeaturesResources.cs.xlf

@@ -22,9 +22,9 @@
         <target state="translated">Akce nemůžou zůstat prázdné.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>

src/Features/Core/Portable/xlf/FeaturesResources.de.xlf

@@ -22,9 +22,9 @@
         <target state="translated">Aktionen dürfen nicht leer sein.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>

src/Features/Core/Portable/xlf/FeaturesResources.es.xlf

@@ -22,9 +22,9 @@
         <target state="translated">Las acciones no pueden estar vacías.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>

src/Features/Core/Portable/xlf/FeaturesResources.fr.xlf

@@ -22,9 +22,9 @@
         <target state="translated">Les actions ne peuvent pas être vides.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>

src/Features/Core/Portable/xlf/FeaturesResources.it.xlf

@@ -22,9 +22,9 @@
         <target state="translated">Il campo Azioni non può essere vuoto.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>

src/Features/Core/Portable/xlf/FeaturesResources.ja.xlf

@@ -22,9 +22,9 @@
         <target state="translated">アクションは空にできません。</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>

src/Features/Core/Portable/xlf/FeaturesResources.ko.xlf

@@ -22,9 +22,9 @@
         <target state="translated">작업은 비워 둘 수 없습니다.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>

src/Features/Core/Portable/xlf/FeaturesResources.pl.xlf

@@ -22,9 +22,9 @@
         <target state="translated">Akcje nie mogą być puste.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>

src/Features/Core/Portable/xlf/FeaturesResources.pt-BR.xlf

@@ -22,9 +22,9 @@
         <target state="translated">Ações não podem ficar vazias.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>

src/Features/Core/Portable/xlf/FeaturesResources.ru.xlf

@@ -22,9 +22,9 @@
         <target state="translated">Действия не могут быть пустыми.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>

src/Features/Core/Portable/xlf/FeaturesResources.tr.xlf

@@ -22,9 +22,9 @@
         <target state="translated">Eylemler boş olamaz.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>

src/Features/Core/Portable/xlf/FeaturesResources.zh-Hans.xlf

@@ -22,9 +22,9 @@
         <target state="translated">操作不能为空。</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>

src/Features/Core/Portable/xlf/FeaturesResources.zh-Hant.xlf

@@ -22,9 +22,9 @@
         <target state="translated">動作不可為空。</target>
         <note />
       </trans-unit>
-      <trans-unit id="Convert_to_query">
-        <source>Convert to query</source>
-        <target state="new">Convert to query</target>
+      <trans-unit id="Convert_to_linq">
+        <source>Convert to LINQ</source>
+        <target state="new">Convert to LINQ</target>
         <note />
       </trans-unit>
       <trans-unit id="Add_to_0">
@@ -37,6 +37,11 @@
         <target state="new">Convert to class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Convert_to_linq_call_form">
+        <source>Convert to LINQ (call form)</source>
+        <target state="new">Convert to LINQ (call form)</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Convert_to_struct">
         <source>Convert to struct</source>
         <target state="new">Convert to struct</target>