Use property pattern matching on union for clearer code

Refactored the Read method to use switch expression with property
pattern matching directly on the union object, instead of switching
on a tuple of boolean flags. This makes the code more idiomatic and
easier to read.

Co-authored-by: Scooletz <scooletz@users.noreply.github.com>
Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>
Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>

Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>

Author: Copilot

src/ModelContextProtocol.Core/Protocol/JsonRpcMessage.cs

@@ -86,57 +86,47 @@ public sealed class Converter : JsonConverter<JsonRpcMessage>
             }
 
             // Determine message type based on presence of id and method properties
-            switch ((union.HasId, union.HasMethod))
+            return union switch
             {
-                case (true, true):
-                    // Messages with both method and id are requests
-                    Debug.Assert(union.Method is not null, "HasMethod should only be true when Method is non-null");
-                    return new JsonRpcRequest
-                    {
-                        JsonRpc = union.JsonRpc,
-                        Id = union.Id,
-                        Method = union.Method!,
-                        Params = union.Params
-                    };
-
-                case (true, false):
-                    // Messages with an id but no method are responses
-                    if (union.HasError)
-                    {
-                        Debug.Assert(union.Error is not null, "HasError should only be true when Error is non-null");
-                        return new JsonRpcError
-                        {
-                            JsonRpc = union.JsonRpc,
-                            Id = union.Id,
-                            Error = union.Error!
-                        };
-                    }
+                // Messages with both method and id are requests
+                { HasId: true, HasMethod: true } => new JsonRpcRequest
+                {
+                    JsonRpc = union.JsonRpc,
+                    Id = union.Id,
+                    Method = union.Method!,
+                    Params = union.Params
+                },
+
+                // Messages with an id and error are error responses
+                { HasId: true, HasError: true } => new JsonRpcError
+                {
+                    JsonRpc = union.JsonRpc,
+                    Id = union.Id,
+                    Error = union.Error!
+                },
 
-                    if (union.HasResult)
-                    {
-                        return new JsonRpcResponse
-                        {
-                            JsonRpc = union.JsonRpc,
-                            Id = union.Id,
-                            Result = union.Result
-                        };
-                    }
+                // Messages with an id and result are success responses
+                { HasId: true, HasResult: true } => new JsonRpcResponse
+                {
+                    JsonRpc = union.JsonRpc,
+                    Id = union.Id,
+                    Result = union.Result
+                },
 
-                    throw new JsonException("Response must have either result or error");
+                // Messages with an id but no method, error, or result are invalid
+                { HasId: true } => throw new JsonException("Response must have either result or error"),
 
-                case (false, true):
-                    // Messages with a method but no id are notifications
-                    Debug.Assert(union.Method is not null, "HasMethod should only be true when Method is non-null");
-                    return new JsonRpcNotification
-                    {
-                        JsonRpc = union.JsonRpc,
-                        Method = union.Method!,
-                        Params = union.Params
-                    };
+                // Messages with a method but no id are notifications
+                { HasMethod: true } => new JsonRpcNotification
+                {
+                    JsonRpc = union.JsonRpc,
+                    Method = union.Method!,
+                    Params = union.Params
+                },
 
-                default:
-                    throw new JsonException("Invalid JSON-RPC message format");
-            }
+                // All other cases are invalid
+                _ => throw new JsonException("Invalid JSON-RPC message format")
+            };
         }
 
         /// <inheritdoc/>