Add code example for CA2251 rule (#49091) (#49092)

Author: kurnakovv

docs/fundamentals/code-analysis/quality-rules/ca2251.md

@@ -32,6 +32,19 @@ The result of a call to <xref:System.String.Compare%2A?displayProperty=nameWithT
 
 To fix violations of this rule, replace the expression comparing the result of <xref:System.String.Compare%2A?displayProperty=nameWithType> with a call to <xref:System.String.Equals%2A?displayProperty=nameWithType>.
 
+## Example
+
+```csharp
+string leftValue = "...";
+string rightValue = "...";
+
+// This code violates the rule.
+bool areEqualUsingCompare = string.Compare(leftValue, rightValue, StringComparison.OrdinalIgnoreCase) == 0;
+
+// This code satisfies the rule.
+bool areEqualUsingEquals = string.Equals(leftValue, rightValue, StringComparison.OrdinalIgnoreCase);
+```
+
 ## When to suppress warnings
 
 It is safe to suppress warnings from this rule.