Set default value in custom control

Question

I am creating custom web control(textbox) which allows only integer data type in textbox. On button submit event if there is no data in textbox, custom control should set TextBox1.Text=0, this is what i want. This is code which i wrote.

public class MasIntTextBox : TextBox
{
    private RequiredFieldValidator req;
    private RegularExpressionValidator regex;
    public string ValGrp { get; set; }
    public string IsRequired { get; set; }//give true/yes or false/no values only

    protected override void OnInit(EventArgs e)
    {
        //this.CssClass = "inp-form";
        if (IsRequired == "true" || IsRequired == "yes")
        {
            req = new RequiredFieldValidator();
            req.ControlToValidate = this.ID;
            req.ErrorMessage = "Enter Numeric Value";
            req.Display = ValidatorDisplay.Dynamic;
            if (!string.IsNullOrEmpty(ValGrp))
                req.ValidationGroup = ValGrp;
            Controls.Add(req);
        }
        regex = new RegularExpressionValidator();
        regex.ControlToValidate = this.ID;
        regex.ErrorMessage = "Numeric Value Only";
        regex.Display = ValidatorDisplay.Dynamic;
        regex.ValidationExpression = "^\\d+(\\.\\d+)?$";
        if (!string.IsNullOrEmpty(ValGrp))
            regex.ValidationGroup = ValGrp;
        Controls.Add(regex);
        //base.OnInit(e);
    }

    protected override void Render(HtmlTextWriter w)
    {
        base.Render(w);
        if (IsRequired == "true" || IsRequired == "yes")
            req.RenderControl(w);
        regex.RenderControl(w);
    }
}

I checked few events or methods for this but they got fired after btnA_click event. I am kind of newbie in this. Any event or method i am missing? Any suggestion accepted. Thanks in Advance...

Answer 1

You should try to set the default value on TextBox.LostFocus event. This event fires immediately after focus is lost from the control (TextBox).