Add test for expressin bodied method.

src/EditorFeatures/CSharpTest/Diagnostics/ImplementInterface/ImplementInterfaceTests.cs

@@ -67,6 +67,20 @@ public async Task TestMethod()
 @"using System; interface IInterface { void Method1 ( ) ; } class Class : IInterface { public void Method1 ( ) { throw new NotImplementedException ( ) ; } } ");
         }
 
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsImplementInterface)]
+        public async Task TestExpressionBodiedMethod1()
+        {
+            await TestWithAllCodeStyleOptionsOnAsync(
+@"interface IInterface { void Method1 ( ) ; } class Class : [|IInterface|] { } ",
+@"using System;
+interface IInterface {
+    void Method1 ( ) ; 
+}
+class Class : IInterface { 
+    public void Method1 ( ) => throw new NotImplementedException ( ) ; 
+}");
+        }
+
         private static readonly string s_tupleElementNamesAttribute =
 @"namespace System.Runtime.CompilerServices
 {

src/Workspaces/CSharp/Portable/CodeGeneration/MethodGenerator.cs

@@ -120,7 +120,8 @@ internal static class MethodGenerator
                     if (expressionBody != null)
                     {
                         return methodDeclaration.WithBody(null)
-                                                .WithExpressionBody(expressionBody);
+                                                .WithExpressionBody(expressionBody)
+                                                .WithSemicolonToken(SyntaxFactory.Token(SyntaxKind.SemicolonToken));
                     }
                 }
             }