Index: clang/lib/Format/TokenAnnotator.cpp
===================================================================
--- clang/lib/Format/TokenAnnotator.cpp
+++ clang/lib/Format/TokenAnnotator.cpp
@@ -2611,6 +2611,10 @@
     return Style.Language == FormatStyle::LK_JavaScript ||
            !Left.TokenText.endswith("=*/");
   if (Right.is(tok::l_paren)) {
+    // using (FileStream fs...
+    if (Style.isCSharp() && Left.is(tok::kw_using) &&
+        Style.SpaceBeforeParens != FormatStyle::SBPO_Never)
+      return true;
     if ((Left.is(tok::r_paren) && Left.is(TT_AttributeParen)) ||
         (Left.is(tok::r_square) && Left.is(TT_AttributeSquare)))
       return true;
Index: clang/unittests/Format/FormatTestCSharp.cpp
===================================================================
--- clang/unittests/Format/FormatTestCSharp.cpp
+++ clang/unittests/Format/FormatTestCSharp.cpp
@@ -165,6 +165,21 @@
                "public string Host {\n  set;\n  get;\n}");
 }
 
+TEST_F(FormatTestCSharp, CSharpUsing) {
+  FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);
+  Style.SpaceBeforeParens = FormatStyle::SBPO_Always;
+  verifyFormat("public void foo() {\n"
+               "  using (StreamWriter sw = new StreamWriter (filenameA)) {}\n"
+               "}",
+               Style);
+
+  Style.SpaceBeforeParens = FormatStyle::SBPO_Never;
+  verifyFormat("public void foo() {\n"
+               "  using(StreamWriter sw = new StreamWriter(filenameB)) {}\n"
+               "}",
+               Style);
+}
+
 TEST_F(FormatTestCSharp, CSharpRegions) {
   verifyFormat("#region aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaa "
                "aaaaaaaaaaaaaaa long region");