Index: clang/lib/Format/TokenAnnotator.cpp
===================================================================
--- clang/lib/Format/TokenAnnotator.cpp
+++ clang/lib/Format/TokenAnnotator.cpp
@@ -3520,6 +3520,17 @@
       return false;
     if (Right.is(TT_CSharpGenericTypeConstraint))
       return true;
+
+    // Break after C# [...] and before public/protected/private/internal.
+    if (Left.is(TT_AttributeSquare) && Left.is(tok::r_square) &&
+        (Right.isAccessSpecifier(/*ColonRequired=*/false) ||
+         Right.is(Keywords.kw_internal)))
+      return true;
+    // Break between ] and [ but only when its really 2 attributes.
+    if (Left.is(TT_AttributeSquare) && Right.is(TT_AttributeSquare) &&
+        Left.is(tok::r_square) && Right.is(tok::l_square))
+      return true;
+
   } else if (Style.Language == FormatStyle::LK_JavaScript) {
     // FIXME: This might apply to other languages and token kinds.
     if (Right.is(tok::string_literal) && Left.is(tok::plus) && Left.Previous &&
Index: clang/unittests/Format/FormatTestCSharp.cpp
===================================================================
--- clang/unittests/Format/FormatTestCSharp.cpp
+++ clang/unittests/Format/FormatTestCSharp.cpp
@@ -247,6 +247,37 @@
   verifyFormat("[TestMethod]\n"
                "public string Host { set; get; }");
 
+  // Adjacent properties should not cause line wrapping issues
+  verifyFormat("[JsonProperty(\"foo\")]\n"
+               "public string Foo { set; get; }\n"
+               "[JsonProperty(\"bar\")]\n"
+               "public string Bar { set; get; }\n"
+               "[JsonProperty(\"bar\")]\n"
+               "protected string Bar { set; get; }\n"
+               "[JsonProperty(\"bar\")]\n"
+               "internal string Bar { set; get; }");
+
+  // Multiple attributes should always be split (not just the first ones)
+  verifyFormat("[XmlIgnore]\n"
+               "[JsonProperty(\"foo\")]\n"
+               "public string Foo { set; get; }");
+
+  verifyFormat("[XmlIgnore]\n"
+               "[JsonProperty(\"foo\")]\n"
+               "public string Foo { set; get; }\n"
+               "[XmlIgnore]\n"
+               "[JsonProperty(\"bar\")]\n"
+               "public string Bar { set; get; }");
+
+  verifyFormat("[XmlIgnore]\n"
+               "[ScriptIgnore]\n"
+               "[JsonProperty(\"foo\")]\n"
+               "public string Foo { set; get; }\n"
+               "[XmlIgnore]\n"
+               "[ScriptIgnore]\n"
+               "[JsonProperty(\"bar\")]\n"
+               "public string Bar { set; get; }");
+
   verifyFormat("[TestMethod(\"start\", HelpText = \"Starts the server "
                "listening on provided host\")]\n"
                "public string Host { set; get; }");
@@ -271,6 +302,34 @@
                "{\n"
                "}");
 
+  verifyFormat("void MethodA([In, Out] ref double x)\n"
+               "{\n"
+               "}");
+
+  verifyFormat("void MethodA([In, Out] double[] x)\n"
+               "{\n"
+               "}");
+
+  verifyFormat("void MethodA([In] double[] x)\n"
+               "{\n"
+               "}");
+
+  verifyFormat("void MethodA(int[] x)\n"
+               "{\n"
+               "}");
+  verifyFormat("void MethodA(int[][] x)\n"
+               "{\n"
+               "}");
+  verifyFormat("void MethodA([] x)\n"
+               "{\n"
+               "}");
+
+  verifyFormat("public void Log([CallerLineNumber] int line = -1, "
+               "[CallerFilePath] string path = null,\n"
+               "                [CallerMemberName] string name = null)\n"
+               "{\n"
+               "}");
+
   // [] in an attribute do not cause premature line wrapping or indenting.
   verifyFormat(R"(//
 public class A