Fix comma placement after lambda block in variable declarations

src/Workspaces/CSharpTest/Formatting/FormattingTests.cs

@@ -396,6 +396,68 @@ class C
             }
             """);
 
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/10526")]
+    public Task LambdaListWithComma()
+        => AssertNoFormattingChangesAsync("""
+            using System;
+
+            class Test
+            {
+                void M()
+                {
+                    Action a = () => { },
+                           b = () => { };
+                }
+            }
+            """);
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/10526")]
+    public Task LambdaListWithCommaMultipleVariables()
+        => AssertNoFormattingChangesAsync("""
+            using System;
+
+            class Test
+            {
+                void M()
+                {
+                    Action a = () => { },
+                           b = () => { },
+                           c = () => { };
+                }
+            }
+            """);
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/10526")]
+    public Task AnonymousMethodListWithComma()
+        => AssertNoFormattingChangesAsync("""
+            using System;
+
+            class Test
+            {
+                void M()
+                {
+                    Action a = delegate { },
+                           b = delegate { };
+                }
+            }
+            """);
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/10526")]
+    public Task ExpressionLambdaListWithComma()
+        => AssertNoFormattingChangesAsync("""
+            using System;
+
+            class Test
+            {
+                void M()
+                {
+                    int x = 1, y = 2;
+                    Func<int> a = () => x,
+                              b = () => y;
+                }
+            }
+            """);
+
     [Fact]
     public Task Scen1()
         => AssertFormatAsync("""

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Formatting/FormattingHelpers.cs

@@ -217,6 +217,12 @@ public static bool IsCommaInAnyArgumentsList(this SyntaxToken token)
             token.Parent.IsAnyArgumentList();
     }
 
+    public static bool IsCommaInVariableDeclaration(this SyntaxToken token)
+    {
+        return token.Kind() == SyntaxKind.CommaToken &&
+            token.Parent.IsKind(SyntaxKind.VariableDeclaration);
+    }
+
     public static bool IsOpenParenOfParenthesizedExpression(this SyntaxToken token)
         => token.Parent is ParenthesizedExpressionSyntax parenthesizedExpression && parenthesizedExpression.OpenParenToken.Equals(token);
 

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Formatting/Rules/TokenBasedFormattingRule.cs

@@ -82,6 +82,7 @@ public override AbstractFormattingRule WithOptions(SyntaxFormattingOptions optio
                         !currentToken.IsCloseParenOfParenthesizedExpression() && // Place ) after } in `(() => {})`
                         !currentToken.IsCommaInInitializerExpression() &&
                         !currentToken.IsCommaInAnyArgumentsList() &&
+                        !currentToken.IsCommaInVariableDeclaration() &&
                         !currentToken.IsCommaInTupleExpression() &&
                         !currentToken.IsCommaInCollectionExpression() &&
                         !currentToken.IsParenInArgumentList() &&