Add C# UI.

src/VisualStudio/CSharp/Impl/Options/Formatting/StyleViewModel.cs

@@ -293,6 +293,25 @@ public C(string s)
 //]
     }
 }
+";
+
+    private static readonly string s_preferNullPropagation = @"
+using System;
+
+class C
+{
+    public C(object o)
+    {
+//[
+        // Prefer:
+        var v = o?.ToString();
+
+        // Over:
+        var v = o == null ? null : o.ToString(); // or
+        var v = o != null ? o.ToString() : null;
+//]
+    }
+}
 ";
 
         private static readonly string s_preferPatternMatchingOverAsWithNullCheck = @"
@@ -620,6 +639,7 @@ internal StyleViewModel(OptionSet optionSet, IServiceProvider serviceProvider) :
             CodeStyleItems.Add(new SimpleCodeStyleOptionViewModel(CodeStyleOptions.PreferThrowExpression, CSharpVSResources.Prefer_throw_expression, s_preferThrowExpression, s_preferThrowExpression, this, optionSet, nullCheckingGroupTitle));
             CodeStyleItems.Add(new SimpleCodeStyleOptionViewModel(CSharpCodeStyleOptions.PreferConditionalDelegateCall, CSharpVSResources.Prefer_conditional_delegate_call, s_preferConditionalDelegateCall, s_preferConditionalDelegateCall, this, optionSet, nullCheckingGroupTitle));
             CodeStyleItems.Add(new SimpleCodeStyleOptionViewModel(CodeStyleOptions.PreferCoalesceExpression, ServicesVSResources.Prefer_coalesce_expression, s_preferCoalesceExpression, s_preferCoalesceExpression, this, optionSet, nullCheckingGroupTitle));
+            CodeStyleItems.Add(new SimpleCodeStyleOptionViewModel(CodeStyleOptions.PreferNullPropagation, ServicesVSResources.Prefer_null_propagation, s_preferNullPropagation, s_preferNullPropagation, this, optionSet, nullCheckingGroupTitle));
         }
     }
 }
\ No newline at end of file

src/VisualStudio/Core/Def/ServicesVSResources.Designer.cs

@@ -1392,6 +1392,15 @@ internal class ServicesVSResources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Prefer null propagation.
+        /// </summary>
+        internal static string Prefer_null_propagation {
+            get {
+                return ResourceManager.GetString("Prefer_null_propagation", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Prefer object initializer.
         /// </summary>

src/VisualStudio/Core/Def/ServicesVSResources.resx

@@ -807,4 +807,7 @@ Additional information: {1}</value>
   <data name="Prefer_coalesce_expression" xml:space="preserve">
     <value>Prefer coalesce expression</value>
   </data>
+  <data name="Prefer_null_propagation" xml:space="preserve">
+    <value>Prefer null propagation</value>
+  </data>
 </root>
\ No newline at end of file