inherit from asp:validationsummary

Question

i have the requirement to show a nicely formatted error-message on top of the page (or control).

therefore i implemented the render method of a new created server control. the new created control inherits from ValidationSummary.

public class AgValidationSummary : ValidationSummary
{
    protected override void Render(System.Web.UI.HtmlTextWriter writer)
    {
        if(this.Enabled)
        {
            if (Page.IsPostBack && !Page.IsValid)
            {

my problem is now, that if an button is fired and his property CausesValidation is set to false my validationsummary will throw an exception because i ask about the Page.IsValid property (and this is only set if there was an call to Page.validate().

has somebody a solution for the problem?

Answer 1

the solution is somehow easy:
just don't parse the Page.IsValid flag :) instead do something like that in your void Render(HtmlTextWriter writer):

if (!this.Enabled)
{
    return;
}

if (this.Page != null)
{
    this.Page.VerifyRenderingInServerForm(this);
}
else
{
    return;
}

var failedValidators = this.Page.Validators.OfType<BaseValidator>().Where(bv => string.Equals(bv.ValidationGroup, this.ValidationGroup) && !bv.IsValid).ToList();

if (failedValidators.Any())
{
    writer.Write(this.HeaderText);
    foreach (var failedValidator in failedValidators)
    {
        writer.Write(failedValidator.ErrorMessage);
    }
}

The reason why this works:
The control, which causes the postback, has got the information about

1. CausesValidation
2. ValidationGroup
3. and other stuff

So the ASP.net-engine itself will execute the associated validators and set them to IsValid or not.

edit
To get rid of the original HeaderText (which is still rendered):

protected override void AddAttributesToRender(HtmlTextWriter writer)
{
    // overwrite to hide the original HeaderText
}