Merge pull request dotnet#1799 from svick/patch-5

Fixed VB code and syntax highlighting

Author: Ron Petrusha

docs/csharp/language-reference/operators/null-conditional-operators.md

@@ -33,48 +33,51 @@ Used to test for null before performing a member access (`?.`) or index (`?[`) o
 int? length = customers?.Length; // null if customers is null   
 Customer first = customers?[0];  // null if customers is null  
 int? count = customers?[0]?.Orders?.Count();  // null if customers, the first customer, or Orders is null  
-  
 ```  
 
 ```vb  
-Dim length = customers?.Length  ‘’ null if customers is null  
-Dim first as Customer = customers?(0);  ‘’ null if customers is null  
-Dim count as Integer? = customers?[0]?.Orders?.Count();  // null if customers, the first customer, or Orders is null  
-  
+Dim length = customers?.Length  ' null if customers is null  
+Dim first as Customer = customers?(0)  ' null if customers is null  
+Dim count as Integer? = customers?(0)?.Orders?.Count()  ' null if customers, the first customer, or Orders is null  
 ```  
 
  The last example demonstrates that the null-condition operators are short-circuiting.  If one operation in a chain of conditional member access and index operation returns null, then the rest of the chain’s execution stops.  Other operations with lower precedence in the expression continue.  For example, `E` in the following always executes, and the `??` and `==` operations execute.  
 
-```vb-c#  
+```csharp
 A?.B?.C?[0] ?? E  
 A?.B?.C?[0] == E  
-  
+```
+
+```vb
+A?.B?.C?(0) ?? E  
+A?.B?.C?(0) == E  
 ```  
 
  Another use for the null-condition member access is invoking delegates in a thread-safe way with much less code.  The old way requires code like the following:  
 
 ```csharp  
 var handler = this.PropertyChanged;  
 if (handler != null)  
-    handler(…)  
-  
+    handler(…);
 ```  
 
 ```vb  
 Dim handler = AddressOf(Me.PropertyChanged)  
 If handler IsNot Nothing  
     Call handler(…)  
-  
 ```  
 
  The new way is much simpler:  
 
-```vb-c#  
+```csharp
 PropertyChanged?.Invoke(e)  
-  
+```  
+
+```vb
+PropertyChanged?.Invoke(e)
 ```  
 
- The new way is thread-safe because the compiler generates code to evaluate `PropertyChanged` one time only, keeping the result in temporary variable.  
+ The new way is thread-safe because the compiler generates code to evaluate `PropertyChanged` one time only, keeping the result in a temporary variable.  
 
  You need to explicitly call the `Invoke` method because there is no null-conditional delegate invocation syntax `PropertyChanged?(e)`.  There were too many ambiguous parsing situations to allow it.  
 
@@ -88,4 +91,4 @@ PropertyChanged?.Invoke(e)
  [C# Reference](../../../csharp/language-reference/index.md)   
  [C# Programming Guide](../../../csharp/programming-guide/index.md)   
  [Visual Basic Language Reference](../../../visual-basic/language-reference/index.md)   
- [Visual Basic Programming Guide](../../../visual-basic/programming-guide/index.md)
+ [Visual Basic Programming Guide](../../../visual-basic/programming-guide/index.md)