Infopath Validation Gotcha

30 Dec 2010

In an InfoPath form I've been working on, I've used the Validating event to attach some code to do some more complex validation (ie, something that I can't achieve through rules). It's actually not too complicated, and follows the following general syntax:

public void MyField_Validating(object sender, XmlValidatingEventArgs e)
{
    //clear any existing errors
    try {
        this.Errors.Delete("MyErrorName");
    } catch (ArgumentException ex) { /* Error does not exist / has not been added. */ };

    if(MyErrorTest())
    {
        this.Errors.Add(e.Site, "NoEmailsFound", "My error message.");
    }
}

However, it's important to note that during the Validating event the underlying form XML data is placed into a read-only state. This means that if you try and update a "notification" or "errormessage" field as part of a Validating event handler like I was, you will encounter an "InvalidOperationException: Operation is not valid due to the current state of the object". The MSDN reference on the XmlEvent.Validating event also mentions this somewhere on the page.

Hope you've all had a fantastic Christmas, and are looking forward to an exciting new year!

[Edit: I've been having trouble getting the red border to appear when using e.ReportError / this.Errors.Add() for a People Picker control; the validation works as expected as submission is disabled and Ctrl+Shift+I brings up the validation error message, but there is no visual indicator for the error, which is rather annoying. This thread was the only thing I could find about this error, but isn't particularly helpful as it suggests using design-time rules which I would use instead of code-behind, if it were possible...]