Index: clang/lib/Format/UnwrappedLineParser.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineParser.cpp
+++ clang/lib/Format/UnwrappedLineParser.cpp
@@ -1482,8 +1482,8 @@
     }
     case tok::equal:
       // Fat arrows (=>) have tok::TokenKind tok::equal but TokenType
-      // TT_FatArrow. The always start an expression or a child block if
-      // followed by a curly.
+      // 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)) {
@@ -1790,14 +1790,20 @@
   bool HasError = false;
 
   // FIXME: Once we have an expression parser in the UnwrappedLineParser,
-  // replace this by using parseAssigmentExpression() inside.
+  // replace this by using parseAssignmentExpression() inside.
   do {
     if (Style.isCSharp()) {
+      // 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();
-        // Fat arrows can be followed by simple expressions or by child blocks
-        // in curly braces.
         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();
           continue;
         }
@@ -1927,6 +1933,12 @@
         parseBracedList();
       }
       break;
+    case tok::equal:
+      if (Style.isCSharp() && FormatTok->is(TT_FatArrow))
+        parseStructuralElement();
+      else
+        nextToken();
+      break;
     case tok::kw_class:
       if (Style.Language == FormatStyle::LK_JavaScript)
         parseRecord(/*ParseAsExpr=*/true);
Index: clang/unittests/Format/FormatTestCSharp.cpp
===================================================================
--- clang/unittests/Format/FormatTestCSharp.cpp
+++ clang/unittests/Format/FormatTestCSharp.cpp
@@ -640,6 +640,122 @@
     };
 })",
                MicrosoftStyle);
+
+  verifyFormat("void bar()\n"
+               "{\n"
+               "    Function(Val, (Action)(() =>\n"
+               "                           {\n"
+               "                               lock (mylock)\n"
+               "                               {\n"
+               "                                   if (true)\n"
+               "                                   {\n"
+               "                                       A.Remove(item);\n"
+               "                                   }\n"
+               "                               }\n"
+               "                           }));\n"
+               "}",
+               MicrosoftStyle);
+
+  verifyFormat("void baz()\n"
+               "{\n"
+               "    Function(Val, (Action)(() =>\n"
+               "                           {\n"
+               "                               using (var a = new Lock())\n"
+               "                               {\n"
+               "                                   if (true)\n"
+               "                                   {\n"
+               "                                       A.Remove(item);\n"
+               "                                   }\n"
+               "                               }\n"
+               "                           }));\n"
+               "}",
+               MicrosoftStyle);
+
+  verifyFormat("void baz()\n"
+               "{\n"
+               "    Function(Val, (Action)(() =>\n"
+               "                           {\n"
+               "                               if (true)\n"
+               "                               {\n"
+               "                                   A.Remove(item);\n"
+               "                               }\n"
+               "                           }));\n"
+               "}",
+               MicrosoftStyle);
+
+  verifyFormat("void baz()\n"
+               "{\n"
+               "    Function(Val, (Action)(() =>\n"
+               "                           {\n"
+               "                               do\n"
+               "                               {\n"
+               "                                   A.Remove(item);\n"
+               "                               } while (true)\n"
+               "                           }));\n"
+               "}",
+               MicrosoftStyle);
+
+  verifyFormat("void baz()\n"
+               "{\n"
+               "    Function(Val, (Action)(() =>\n"
+               "                           { A.Remove(item); }));\n"
+               "}",
+               MicrosoftStyle);
+
+  verifyFormat("void bar()\n"
+               "{\n"
+               "    Function(Val, (() =>\n"
+               "                   {\n"
+               "                       lock (mylock)\n"
+               "                       {\n"
+               "                           if (true)\n"
+               "                           {\n"
+               "                               A.Remove(item);\n"
+               "                           }\n"
+               "                       }\n"
+               "                   }));\n"
+               "}",
+               MicrosoftStyle);
+  verifyFormat("void bar()\n"
+               "{\n"
+               "    Function((() =>\n"
+               "              {\n"
+               "                  lock (mylock)\n"
+               "                  {\n"
+               "                      if (true)\n"
+               "                      {\n"
+               "                          A.Remove(item);\n"
+               "                      }\n"
+               "                  }\n"
+               "              }));\n"
+               "}",
+               MicrosoftStyle);
+
+  MicrosoftStyle.IndentWidth = 2;
+  verifyFormat("void bar()\n"
+               "{\n"
+               "  Function((() =>\n"
+               "            {\n"
+               "              lock (mylock)\n"
+               "              {\n"
+               "                if (true)\n"
+               "                {\n"
+               "                  A.Remove(item);\n"
+               "                }\n"
+               "              }\n"
+               "            }));\n"
+               "}",
+               MicrosoftStyle);
+  verifyFormat("void bar() {\n"
+               "  Function((() => {\n"
+               "    lock (mylock) {\n"
+               "      if (true) {\n"
+               "        A.Remove(item);\n"
+               "      }\n"
+               "    }\n"
+               "  }));\n"
+               "}",
+               GoogleStyle);
 }
 
 TEST_F(FormatTestCSharp, CSharpObjectInitializers) {