✅ Why I'm getting ArgumentException/System.Windows.Markup.XamlParseException exception?

System.Windows.Markup.XamlParseException: ''Failed to create a 'AutoGeneratingColumn' from the text 'dg_input_AutoGeneratingColumn'.' Line number '16' and line position '32'.'
ArgumentException: Cannot bind to the target method because its signature or security transparency is not compatible with that of the delegate type.

  public partial class ManualInputWindow : Window
  {
      private DataTable _input;
      public ManualInputWindow(DataTable input)
      {
          InitializeComponent();
          ...

    class CustomDataGrid : DataGrid
    {
        public CustomDataGrid() : base()
        {
        }
  ...

        private void Dg_input_AutoGeneratingColumn(object sender, DataGridAutoGeneratingColumnEventArgs e)
        {
            if (e.Column is DataGridTextColumn column)
            {
                ((Binding)column.Binding).Converter = new StringEmpty_to_Null_Converter();
            }
            else if (e.Column is DataGridCheckBoxColumn column1)
            {
                if (_input.Columns[e.PropertyName].AllowDBNull)
                {
                    column1.IsThreeState = true;
                    ((Binding)column1.Binding).Converter = new NullToDBNullConverter();
                }
            }
        }