I am trying to create check box control field data type from contour check box and having problem with Mandatory field set up.

When i add this new data type on form with Mandatory requirement ON - i get this below error when i try to run the form which has this control.

Control 'b1998910_dd75_4dc2_bf58_563b5779dfca' referenced by the ControlToValidate property of 'mandatory' cannot be validated.

This is my full code for the extension. Please help. Thanks in advance.

namespace CheckedCheckBox.FieldType
{
    public class CheckedCheckBox : Umbraco.Forms.Core.FieldType
    {
        public Control.CheckedCheckBox chkCheckBox;
        public List<Object> Value;

    
        public CheckedCheckBox()
        {
            Id = new Guid("1A78EF46-E782-461C-AA6B-E6C30D9746B9");
           
            Name = "Check box - default Checked";
            Description = "Check box with default checked";

            Icon = "checkbox.png";
            DataType = FieldDataType.Bit;

            chkCheckBox = new Control.CheckedCheckBox();

            Value = new List<object>();
        }


        public override WebControl Editor
        {
            get
            {
                return chkCheckBox;
            }
            set { base.Editor = value; }
        }
      
        public override List<Object> Values
        {
            get
            {
                if (chkCheckBox.Checked)
                {
                    Value.Clear();
                    Value.Add(true);
                }
                else
                {
                    Value.Clear();
                    Value.Add(false);
                }
                return Value;
            }
            set { Value = value; }
        }

        public override string RenderPreview()
        {
            return "<INPUT TYPE=\"checkbox\" id=\"check-CheckBox\" checked />";
       
        }

        public override string RenderPreviewWithPrevalues(List<object> prevalues)
        {
            return RenderPreview();
        }

        public override bool SupportsRegex
        {
            get { return true; }
        }
 
    }
}