Use-throw-expression should not be offered when the 'if-block' has additional statements in it.

src/EditorFeatures/CSharpTest/UseThrowExpression/UseThrowExpressionTests.cs

@@ -386,6 +386,48 @@ public C(int? x)
 
         _x = x;
     }
+}");
+        }
+
+        [WorkItem(19377, "https://github.com/dotnet/roslyn/issues/19377")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseThrowExpression)]
+        public async Task TestNotWithMultipleStatementsInIf1()
+        {
+            await TestMissingInRegularAndScriptAsync(
+@"using System;
+
+class C
+{
+    void M(string s)
+    {
+        if (s == null)
+        {
+            Console.WriteLine();
+            [|throw|] new ArgumentNullException(nameof(s));
+        }
+        _s = s;
+    }
+}");
+        }
+
+        [WorkItem(19377, "https://github.com/dotnet/roslyn/issues/19377")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseThrowExpression)]
+        public async Task TestNotWithMultipleStatementsInIf2()
+        {
+            await TestMissingInRegularAndScriptAsync(
+@"using System;
+
+class C
+{
+    void M(string s)
+    {
+        if (s == null)
+        {
+            [|throw|] new ArgumentNullException(nameof(s));
+            Console.WriteLine();
+        }
+        _s = s;
+    }
 }");
         }
     }

src/Features/Core/Portable/UseThrowExpression/AbstractUseThrowExpressionDiagnosticAnalyzer.cs

@@ -116,6 +116,12 @@ private void AnalyzeOperation(OperationAnalysisContext context, INamedTypeSymbol
                 return;
             }
 
+            if (!IsOnlyStatementOfIf(ifOperation, throwOperation))
+            {
+                // The if-statement can only have a single throw-statement in it.
+                return;
+            }
+
             var containingBlock = GetOperation(
                 semanticModel, ifOperation.Syntax.Parent, cancellationToken) as IBlockStatement;
             if (containingBlock == null)
@@ -189,6 +195,18 @@ private void AnalyzeOperation(OperationAnalysisContext context, INamedTypeSymbol
             }
         }
 
+        private bool IsOnlyStatementOfIf(IIfStatement ifOperation, IThrowStatement throwStatement)
+        {
+            if (ifOperation.IfTrueStatement.Syntax == throwStatement.Syntax)
+            {
+                return true;
+            }
+
+            return ifOperation.IfTrueStatement is IBlockStatement block &&
+                   block.Statements.Length == 1 &&
+                   block.Statements[0].Syntax == throwStatement.Syntax;
+        }
+
         protected abstract ISyntaxFactsService GetSyntaxFactsService();
         protected abstract ISemanticFactsService GetSemanticFactsService();