# Microsoft.Extensions.FileSystemGlobbing.Internal.PatternContexts

``` diff
 namespace Microsoft.Extensions.FileSystemGlobbing.Internal.PatternContexts {
-    public abstract class PatternContext<TFrame> : IPatternContext
+    public abstract class PatternContext<TFrame> : IPatternContext where TFrame : struct
     public abstract class PatternContextLinear : PatternContext<PatternContextLinear.FrameData> {
         public struct FrameData {
-            public string Stem { get; }
+            public string? Stem { get; }
         }
     }
     public abstract class PatternContextRagged : PatternContext<PatternContextRagged.FrameData> {
         public struct FrameData {
-            public string Stem { get; }
+            public string? Stem { get; }
         }
     }
 }
```

