pythonnet · Legion-ale · Sep 23, 2025 · Sep 30, 2025
diff --git a/src/runtime/StateSerialization/NoopFormatter.cs b/src/runtime/StateSerialization/NoopFormatter.cs
@@ -5,7 +5,11 @@
 namespace Python.Runtime;

 public class NoopFormatter : IFormatter {
-    public object Deserialize(Stream s) => throw new NotImplementedException();
+
+    public object Deserialize(Stream s) => throw new NotImplementedException(
+        "Cannot deserialize using 'NoopFormatter', implement 'Python.Runtime.RuntimeData.FormatterType' if needed"
+    );
+
    public void Serialize(Stream s, object o) {}

    public SerializationBinder? Binder { get; set; }

diff --git a/src/runtime/StateSerialization/RuntimeData.cs b/src/runtime/StateSerialization/RuntimeData.cs
@@ -15,16 +15,41 @@ namespace Python.Runtime
 {
    public static class RuntimeData
    {
+        //TODO: put it in a utility class instead of inside the RuntimeData Class.
+        private static Version? GetNetVersion(string verToCheck)
+        {
+            // Examples:
+            // ".NET 8.0.0"
+            // ".NET 9.0.0"
+            // ".NET Framework 4.8.1"
+            // ".NET Core 3.1.32"
+            string desc = RuntimeInformation.FrameworkDescription;
+            if (desc.StartsWith(verToCheck, StringComparison.OrdinalIgnoreCase))
+            {
+                var verStr = desc.Split(' ').Last();
+                if (Version.TryParse(verStr, out var ver))
+                    return ver;
+            }
+            return null;
+        }

        public readonly static Func<IFormatter> DefaultFormatterFactory = () =>
        {
-            try
+            //The issue here is that just instancing BynaryFormatter doesn't solve the problem.
+            //you need to use it to generate the exception.
+            /*try
            {
                return new BinaryFormatter();
            }
            catch
            {
                return new NoopFormatter();
+            }*/
+            var ver = GetNetVersion(".NET");
+            if(ver != null && ver.Major >= 9) {
+                return new NoopFormatter();
+            } else {
+                return new BinaryFormatter();
            }
        };