Add generic type argument accessibility example to CS0050 documentation (#47705)

* Initial plan

* Add generic type argument accessibility example to CS0050 documentation

Co-authored-by: BillWagner <[email protected]>

* Apply suggestions from code review

Co-authored-by: Genevieve Warren <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: BillWagner <[email protected]>
Co-authored-by: Bill Wagner <[email protected]>
Co-authored-by: Genevieve Warren <[email protected]>

Author: 3 people

docs/csharp/language-reference/compiler-messages/cs0050.md

@@ -12,9 +12,9 @@ ms.assetid: dead2d28-f4db-4afe-b8dd-38968625f7c3
 
 Inconsistent accessibility: return type 'type' is less accessible than method 'method'
 
- The return type and each of the types referenced in the formal parameter list of a method must be at least as accessible as the method itself. For more information, see [Access Modifiers](../../programming-guide/classes-and-structs/access-modifiers.md).
+ The return type and each of the types referenced in the formal parameter list of a method must be at least as accessible as the method itself. This includes type arguments of generic types used in the return type or parameters. For more information, see [Access Modifiers](../../programming-guide/classes-and-structs/access-modifiers.md).
 
-## Example
+## Examples
 
  The following sample generates CS0050 because no accessibility modifier is supplied for `MyClass`, and its accessibility therefore defaults to `private`:
 
@@ -36,3 +36,43 @@ public class MyClass2
     public static void Main() { }
 }
 ```
+
+CS0050 can also occur when a generic type's type argument is less accessible than the method:
+
+```csharp
+// CS0050_Generic.cs
+using System.Collections.ObjectModel;
+
+internal class CeisData // Internal class
+{
+    public string Name { get; set; }
+}
+
+public class MyClass
+{
+    public static ObservableCollection<CeisData> BuildCeis()   // CS0050
+    {
+        return new ObservableCollection<CeisData>();
+    }
+}
+```
+
+To fix this error, make the type argument at least as accessible as the method:
+
+```csharp
+// Fixed version
+using System.Collections.ObjectModel;
+
+public class CeisData // Now public
+{
+    public string Name { get; set; }
+}
+
+public class MyClass
+{
+    public static ObservableCollection<CeisData> BuildCeis()   // OK
+    {
+        return new ObservableCollection<CeisData>();
+    }
+}
+```