Add code example for CA2201 rule (#49058)

docs/fundamentals/code-analysis/quality-rules/ca2201.md

@@ -10,6 +10,8 @@ helpviewer_keywords:
 - DoNotRaiseReservedExceptionTypes
 author: gewarren
 ms.author: gewarren
+dev_langs:
+- CSharp
 ---
 # CA2201: Do not raise reserved exception types
 
@@ -78,6 +80,29 @@ For all other situations, consider creating your own type that derives from <xre
 
 To fix a violation of this rule, change the type of the thrown exception to a specific type that's not one of the reserved types.
 
+## Example
+
+```csharp
+// This code violates the rule.
+throw new Exception();
+throw new NullReferenceException();
+throw new IndexOutOfRangeException();
+// ...
+
+// This code satisfies the rule.
+throw new ArgumentException();
+throw new ArgumentNullException();
+throw new InvalidOperationException();
+// ...
+
+// A minimal implementation of inheritance from Exception
+public class CustomException : Exception { }
+
+// Or create your own type that derives from Exception
+// This code satisfies the rule too.
+throw new CustomException();
+```
+
 ## When to suppress warnings
 
 Do not suppress a warning from this rule.