dotnet/wpf · warning · ArgumentException

SR.SerializerProviderNotRegistered

Error message

SR.SerializerProviderNotRegistered

What it means

SerializerProvider.UnregisterSerializer deletes the registry subkey '{DisplayName}/{AssemblyName}/{AssemblyVersion}/{WinFXVersion}' for the given descriptor. If no such key exists, it throws ArgumentException (SR.SerializerProviderNotRegistered) with the serializer key as paramName — you cannot unregister a serializer that was never registered.

Solutions

  1. Verify registration first (open the registry key or attempt RegisterSerializer semantics) before calling UnregisterSerializer
  2. Catch ArgumentException and treat 'not registered' as a no-op success in uninstall code
  3. Ensure the descriptor passed matches the original registration exactly (same DisplayName, AssemblyName, AssemblyVersion, WinFXVersion)
  4. Manually delete the stale plugin subkey under the serializer plugins registry path if descriptors cannot be reconstructed

Example fix

// before
SerializerProvider.UnregisterSerializer(descriptor); // throws if absent
// after
try { SerializerProvider.UnregisterSerializer(descriptor); }
catch (ArgumentException) { /* not registered - nothing to do */ }
Defensive patterns

Strategy: try-catch

Validate before calling

using Microsoft.Win32;
bool SerializerKeyExists(RegistryKey root, string pluginsPath, SerializerDescriptor d) {
    using var plugins = root.OpenSubKey(pluginsPath);
    var key = $"{d.DisplayName}/{d.AssemblyName}/{d.AssemblyVersion}/{d.WinFXVersion}";
    using var k = plugins?.OpenSubKey(key);
    return k != null;
}

Try / catch

try { SerializerProvider.UnregisterSerializer(descriptor); }
catch (ArgumentException) { /* not registered - no-op */ }

Prevention

When it happens

Trigger: Calling UnregisterSerializer with a descriptor whose registration key is absent: never registered, already uninstalled, or registered with different DisplayName/AssemblyName/AssemblyVersion/WinFXVersion values than the descriptor passed now.

Common situations: Uninstaller removing a plugin twice; unregistration using a descriptor whose version differs from the one originally registered; cleaning a machine where the plugin registry was manually edited.

Understand the failure class

Background: Record Not Found Errors: "not found", RecordNotFound, and "was not found" — what they mean and how to fix them — this error's family across 28 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/be645e87166d9770. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Documents/Serialization/SerializerProvider.cs:105

        /// <summary>
        /// Un-Registers the serializer plug-in identified by serializerDescriptor in the registry
        /// </summary>
        /// <remarks>
        ///     Removes a previously installed plug-n serialiazer from the registry
        ///
        ///     This method currently requires full trust to run.
        /// </remarks>
        public static void UnregisterSerializer(SerializerDescriptor serializerDescriptor)
        {

            ArgumentNullException.ThrowIfNull(serializerDescriptor);

            RegistryKey plugIns = _rootKey.CreateSubKey(_registryPath);
            string serializerKey = $"{serializerDescriptor.DisplayName}/{serializerDescriptor.AssemblyName}/{serializerDescriptor.AssemblyVersion}/{serializerDescriptor.WinFXVersion}";

            if (plugIns.OpenSubKey(serializerKey) == null)
            {
                throw new ArgumentException(SR.SerializerProviderNotRegistered, serializerKey);
            }

            plugIns.DeleteSubKeyTree(serializerKey);
        }

        /// <summary>
        /// Create a SerializerWriter identified by the passed in SerializerDescriptor on the passed in stream
        /// </summary>
        /// <remarks>
        ///     With a SerializerProvider (which requires full trust to ctor) and a SerializerDescriptor (which requires
        ///     full trust to obtain) create a SerializerWriter
        ///
        ///     This method currently requires full trust to run.
        /// </remarks>
        public SerializerWriter CreateSerializerWriter(SerializerDescriptor serializerDescriptor, Stream stream)
        {

            SerializerWriter serializerWriter = null;

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