Index: clang/lib/Format/TokenAnnotator.cpp
===================================================================
--- clang/lib/Format/TokenAnnotator.cpp
+++ clang/lib/Format/TokenAnnotator.cpp
@@ -3717,6 +3717,9 @@
     return true;
 
   if (Style.isCSharp()) {
+    if (Left.is(TT_FatArrow) && Right.is(tok::l_brace) &&
+        Style.BraceWrapping.AfterFunction)
+      return true;
     if (Right.is(TT_CSharpNamedArgumentColon) ||
         Left.is(TT_CSharpNamedArgumentColon))
       return false;
Index: clang/lib/Format/UnwrappedLineParser.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineParser.cpp
+++ clang/lib/Format/UnwrappedLineParser.cpp
@@ -1638,19 +1638,8 @@
       break;
     }
     case tok::equal:
-      // Fat arrows (=>) have tok::TokenKind tok::equal but TokenType
-      // TT_FatArrow. They always start an expression or a child block if
-      // followed by a curly brace.
       if (FormatTok->is(TT_FatArrow)) {
-        nextToken();
-        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();
-        }
+        tryToParseCSharpLambda();
         break;
       }
 
@@ -1726,7 +1715,7 @@
   // Try to parse the property accessor:
   // https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/properties
   Tokens->setPosition(StoredPosition);
-  if (!IsTrivialPropertyAccessor && Style.BraceWrapping.AfterFunction == true)
+  if (!IsTrivialPropertyAccessor && Style.BraceWrapping.AfterFunction)
     addUnwrappedLine();
   nextToken();
   do {
@@ -1942,17 +1931,13 @@
 }
 
 bool UnwrappedLineParser::tryToParseCSharpLambda() {
-  // Fat arrows (=>) have tok::TokenKind tok::equal but TokenType
-  // TT_FatArrow. They always start an expression or a child block if
-  // followed by a curly brace.
+  assert(FormatTok->is(TT_FatArrow));
+  // Fat arrows (=>) have tok::TokenKind tok::equal but TokenType TT_FatArrow.
+  // They always start an expression or a child block if followed by a curly
+  // brace.
   nextToken();
   if (FormatTok->isNot(tok::l_brace))
     return false;
-  // C# may break after => if the next character is a newline.
-  if (Style.BraceWrapping.AfterFunction) {
-    // calling `addUnwrappedLine()` here causes odd parsing errors.
-    FormatTok->MustBreakBefore = true;
-  }
   parseChildBlock();
   return true;
 }
@@ -1965,24 +1950,17 @@
   // FIXME: Once we have an expression parser in the UnwrappedLineParser,
   // replace this by using parseAssignmentExpression() inside.
   do {
-    if (Style.isCSharp() && FormatTok->is(TT_FatArrow))
-      if (tryToParseCSharpLambda())
-        continue;
+    if (Style.isCSharp() && FormatTok->is(TT_FatArrow) &&
+        tryToParseCSharpLambda())
+      continue;
     if (Style.Language == FormatStyle::LK_JavaScript) {
       if (FormatTok->is(Keywords.kw_function) ||
           FormatTok->startsSequence(Keywords.kw_async, Keywords.kw_function)) {
         tryToParseJSFunction();
         continue;
       }
-      if (FormatTok->is(TT_FatArrow)) {
-        nextToken();
-        // Fat arrows can be followed by simple expressions or by child blocks
-        // in curly braces.
-        if (FormatTok->is(tok::l_brace)) {
-          parseChildBlock();
-          continue;
-        }
-      }
+      if (FormatTok->is(TT_FatArrow) && tryToParseCSharpLambda())
+        continue;
       if (FormatTok->is(tok::l_brace)) {
         // Could be a method inside of a braced list `{a() { return 1; }}`.
         if (tryToParseBracedList())