Question

I have a textbox in a WPF application bound to a property on a Linq to Entities class that implements IDataErrorInfo. The textbox binding has ValidatesOnExceptions=True and ValidatesOnDataErrors=True. When the textbox is bound to an integer property and the user enters text then the textbox outline displays as red as I haven’t set up a custom style.

In my Save method how do I know the object can’t be saved as it’s invalid? I’d prefer the user clicks the Save button and I can notify them of a problem rather than disabling the Save button.

Cheers,

Dave

Answer 1

I haven’t found an easy way to do it. I found some code around the traps to recurse through all the controls on the form and determine if any of them have validation errors. I ended up turning it into an extension method:

// Validate all dependency objects in a window internal static IList<ValidationError> GetErrors(this DependencyObject node) {     // Check if dependency object was passed     if (node != null)     {         // Check if dependency object is valid.         // NOTE: Validation.GetHasError works for controls that have validation rules attached          bool isValid = !Validation.GetHasError(node);         if (!isValid)         {             // If the dependency object is invalid, and it can receive the focus,             // set the focus             if (node is IInputElement) Keyboard.Focus((IInputElement)node);             return Validation.GetErrors(node);         }     }      // If this dependency object is valid, check all child dependency objects     foreach (object subnode in LogicalTreeHelper.GetChildren(node))     {         if (subnode is DependencyObject)         {             // If a child dependency object is invalid, return false immediately,             // otherwise keep checking             var errors = GetErrors((DependencyObject)subnode);             if (errors.Count > 0) return errors;         }     }      // All dependency objects are valid     return new ValidationError[0]; } 

So then when the user clicks the Save button on a form, I do this:

var errors = this.GetErrors(); if (errors.Count > 0) {     MessageBox.Show(errors[0].ErrorContent.ToString());     return; } 

It’s a lot more work than it should be, but using the extension method simplifies it a bit.