Custom Server Control Textfield

[m_bo]

Hi,
I wrote my Server Control Textfield by inherits from Ext.Net.Textfield.
When I use it in a form I get always empty string in it's Text value in code behind during form submit.
It happens only with my textfield because if I use the basic textfield I have no problem.
Do I miss something? Thank you
My Server Control code

    public class MyTextField : Ext.Net.TextField
    {
        [Category("Text")]
        string _id = "";

        public MyTextField():base()
        {
          
        }

        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);
            this.ID = id;
            
        }

        public string id
        {
            get { return _id; }
            set
            {
                _id = value;

            }
        }
}