Add code example for CA2257 rule (#49109) (#49110)

Author: kurnakovv

docs/fundamentals/code-analysis/quality-rules/ca2257.md

@@ -9,6 +9,8 @@ helpviewer_keywords:
 - DynamicInterfaceCastableImplementationAnalyzer
 - CA2257
 author: Youssef1313
+dev_langs:
+- CSharp
 ---
 # CA2257: Members defined on an interface with the 'DynamicInterfaceCastableImplementationAttribute' should be 'static'
 
@@ -32,10 +34,15 @@ Since a type that implements `IDynamicInterfaceCastable` may not implement a dyn
 
 Mark the interface member `static`.
 
+## Example
+
+:::code language="csharp" source="snippets/csharp/all-rules/ca2257.cs" id="snippet1":::
+
 ## When to suppress errors
 
 Do not suppress a warning from this rule.
 
 ## See also
 
 - [Usage warnings](usage-warnings.md)
+- [CA2256: All members declared in parent interfaces must have an implementation in a DynamicInterfaceCastableImplementation-attributed interface](ca2256.md)

docs/fundamentals/code-analysis/quality-rules/snippets/csharp/all-rules/ca2257.cs

@@ -0,0 +1,19 @@
+using System.Runtime.InteropServices;
+
+namespace ca2257
+{
+    //<snippet1>
+    [DynamicInterfaceCastableImplementation]
+    interface IExample
+    {
+        // This method violates the rule.
+        void BadMethod();
+
+        // This method satisfies the rule.
+        static void GoodMethod()
+        {
+            // ...
+        }
+    }
+    //</snippet1>
+}