public class MySyntax : RadSyntaxEditor
{
    protected override bool IsInputChar(char charCode)
    {
        return base.IsInputChar(charCode) || char.IsLetterOrDigit(charCode); 
    }
    public override string ThemeClassName
    {
        get
        {
            return typeof(RadSyntaxEditor).FullName;
        }
        set
        {
            base.ThemeClassName = value;
        }
    }
}