图像控制所需的字段验证器

Question

Old Title: Prevent dynamically created control from retaining value

Old Info: The reason I need to do this is because I am trying to create a work around for a required field validator for an Image control. The way my code works is I have a Image control beside a Button, a user clicks on the button and then is prompted to upload an image. I need to ensure that an image is uploaded before the user can move onto the next stage.

Since there is no required field validator for an image control, I created a textbox which is suppose to display the imageURL of the image control every time the image control is recreated on postbacks. However, the textbox always retains the value from the initial creation of the control.

* Note: all controls on the page are dynamically created.

The first thing I do is create the image control and add it to an HTML Table. This works fine. Right after that I find the table cell and add the textbox to the cell that has an image control:

HtmlTableCell tc = (HtmlTableCell)customProperties.FindControl("tcControl_" + (i + 1).ToString());
RadBinaryImage rbi = (RadBinaryImage)customProperties.FindControl("CustomControl" + (i + 1).ToString());

TextBox photoValue = new TextBox();
photoValue.ID = "CustomControl" + (i + 1).ToString() + "_txt";
photoValue.Text = rbi.imageUrl;

This occurs everytime I create all the controls. For all the controls they all retain their values, this is the only control which I don't want this to happen. Does anyone know of how this can be done? Or another way of validating an image control?

Thanks for your time, All comments/answers are appreciated (:

SOLVED:

I created a modified version of a checkboxlist required field validator that I found here. Here is the code: I replaced the namespace with ######## for security reasons.

using System;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;
using Telerik.Web.UI;

namespace #######################################
{
    public class RequiredFieldValidatorForImages :
                        System.Web.UI.WebControls.BaseValidator
    {
        private Control _ctrl;

        public RequiredFieldValidatorForImages()
        {
            base.EnableClientScript = false;
        }

        protected override bool ControlPropertiesValid()
        {
            Control ctrl = FindControl(ControlToValidate);

            if (ctrl != null)
            {
                _ctrl = (Control)ctrl;
                return (_ctrl != null);
            }
            else
                return false;  // raise exception
        }

        protected override bool EvaluateIsValid()
        {
            try
            {
                Image rbi = (Image)_ctrl;
                return rbi.ImageUrl != "~/images/noimages.jpg";
            }
            catch
            {
                RadBinaryImage rbi = (RadBinaryImage)_ctrl;
                return rbi.ImageUrl != "~/images/noimages.jpg";
            }
        }
    }
}

Answer 1

Solved:

I created a modified version of a checkboxlist required field validator that I found here. Here is the code: I replaced the namespace with ######## for security reasons.

using System;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;
using Telerik.Web.UI;

namespace #######################################
{
    public class RequiredFieldValidatorForImages :
                        System.Web.UI.WebControls.BaseValidator
    {
        private Control _ctrl;

        public RequiredFieldValidatorForImages()
        {
            base.EnableClientScript = false;
        }

        protected override bool ControlPropertiesValid()
        {
            Control ctrl = FindControl(ControlToValidate);

            if (ctrl != null)
            {
                _ctrl = (Control)ctrl;
                return (_ctrl != null);
            }
            else
                return false;  // raise exception
        }

        protected override bool EvaluateIsValid()
        {
            try
            {
                Image rbi = (Image)_ctrl;
                return rbi.ImageUrl != "~/images/noimages.jpg";
            }
            catch
            {
                RadBinaryImage rbi = (RadBinaryImage)_ctrl;
                return rbi.ImageUrl != "~/images/noimages.jpg";
            }
        }
    }
}