Add code example for CA1823 rule (#48966) (#48967)

Author: kurnakovv

docs/fundamentals/code-analysis/quality-rules/ca1823.md

@@ -10,6 +10,8 @@ helpviewer_keywords:
 - CA1823
 author: gewarren
 ms.author: gewarren
+dev_langs:
+- CSharp
 ---
 # CA1823: Avoid unused private fields
 
@@ -33,6 +35,10 @@ Private fields were detected that do not appear to be accessed in the assembly.
 
 To fix a violation of this rule, remove the field or add code that uses it.
 
+## Example
+
+:::code language="csharp" source="snippets/csharp/all-rules/ca1823.cs" id="snippet1":::
+
 ## When to suppress warnings
 
 It is safe to suppress a warning from this rule.
@@ -60,3 +66,4 @@ For more information, see [How to suppress code analysis warnings](../suppress-w
 
 - [CA1812: Avoid uninstantiated internal classes](ca1812.md)
 - [CA1801: Review unused parameters](ca1801.md)
+- [Remove unread private member (IDE0052)](../style-rules/ide0052.md)

docs/fundamentals/code-analysis/quality-rules/snippets/csharp/all-rules/ca1823.cs

@@ -0,0 +1,24 @@
+namespace ca1823
+{
+    //<snippet1>
+    public class User
+    {
+        private readonly string _firstName;
+        private readonly string _lastName;
+
+        // CA1823: Unused field '_age'
+        private readonly int _age;
+
+        public User(string firstName, string lastName)
+        {
+            _firstName = firstName;
+            _lastName = lastName;
+        }
+
+        public string GetFullName()
+        {
+            return $"My name is {_firstName} {_lastName}";
+        }
+    }
+    //</snippet1>
+}