I’m currently at a customer in Hannover and was asked how to change the background color of a textbox from the client side validation method called by a CustomValidator control.
Here is a sample how to access the pages validation properties including the one from the custom validator:
function validateRequired(sender, args)
{
if (args.Value == null) return;
if (args.Value.length > 0) return;
args.IsValid = false;
var txt = $get(sender.controltovalidate);
if (txt)
{
txt.style.backgroundColor = '#ff0000';
}
}
I wrapped the stuff in a server control derived from the custom validator control:
public class RequiredValidator
: CustomValidator
{
protected override void OnInit(EventArgs e)
{
var ctrl = Parent.FindControl(ControlToValidate);
if (ctrl == null)
{
throw new InvalidOperationException(
"ControlToValidate not found.");
}
var txt = ctrl as TextBox;
if (txt == null)
{
throw new InvalidOperationException(
"ControlToValidate is not a textbox.");
}
if (!Page.ClientScript.IsClientScriptBlockRegistered(
typeof(CustomValidator), "RequiredValidator"))
{
Page.ClientScript.RegisterClientScriptBlock(
typeof(CustomValidator),
"RequiredValidator",
string.Concat(
"<script type=\"text/javascript\">\n//<![CDATA[\n",
Resources.RequiredValidator,
"\n//]]>\n</script>"));
}
base.OnInit(e);
ClientValidationFunction =
string.Concat(
"validateRequired");
ServerValidate += RequiredValidator_ServerValidate;
EnableClientScript = true;
ValidateEmptyText = true;
}
private void RequiredValidator_ServerValidate(
object source,
ServerValidateEventArgs args)
{
var ctrl = Parent.FindControl(ControlToValidate);
if (ctrl == null)
{
throw new InvalidOperationException(
"ControlToValidate not found.");
}
var txt = ctrl as TextBox;
if (txt == null)
{
throw new InvalidOperationException(
"ControlToValidate is not a textbox.");
}
if (!string.IsNullOrEmpty(txt.Text)) return;
txt.BackColor = Color.Red;
args.IsValid = false;
}
}