Index: clang/lib/Format/UnwrappedLineParser.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineParser.cpp
+++ clang/lib/Format/UnwrappedLineParser.cpp
@@ -1459,8 +1459,14 @@
       // followed by a curly.
       if (FormatTok->is(TT_JsFatArrow)) {
         nextToken();
-        if (FormatTok->is(tok::l_brace))
+        if (FormatTok->is(tok::l_brace)) {
+          // C# may break after => if the next character is a newline.
+          if (Style.isCSharp() && Style.BraceWrapping.AfterFunction == true) {
+            // calling `addUnwrappedLine()` here causes odd parsing errors.
+            FormatTok->MustBreakBefore = true;
+          }
           parseChildBlock();
+        }
         break;
       }
 
Index: clang/unittests/Format/FormatTestCSharp.cpp
===================================================================
--- clang/unittests/Format/FormatTestCSharp.cpp
+++ clang/unittests/Format/FormatTestCSharp.cpp
@@ -525,6 +525,33 @@
   EXPECT_EQ(Code, format(Code, Style));
 }
 
+TEST_F(FormatTestCSharp, CSharpLambdas) {
+  FormatStyle GoogleStyle = getGoogleStyle(FormatStyle::LK_CSharp);
+  FormatStyle MicrosoftStyle = getMicrosoftStyle(FormatStyle::LK_CSharp);
+
+  verifyFormat(R"(//
+class MyClass {
+  Action<string> greet = name => {
+    string greeting = $"Hello {name}!";
+    Console.WriteLine(greeting);
+  };
+})",
+               GoogleStyle);
+
+  // Microsoft Style:
+  // https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/statements-expressions-operators/lambda-expressions#statement-lambdas
+  verifyFormat(R"(//
+class MyClass
+{
+    Action<string> greet = name =>
+    {
+        string greeting = $"Hello {name}!";
+        Console.WriteLine(greeting);
+    };
+})",
+               MicrosoftStyle);
+}
+
 TEST_F(FormatTestCSharp, CSharpObjectInitializers) {
   FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);