Best practices for WPF async validations?

Question

Are there any recommendations about performing asynchronous MVVM-ish validations in WPF? Have read about INotifyDataErrorInfo, but unfortunately is only available to Silverlight.

Thanks.

Bahri Gungor · Accepted Answer · 2011-09-08 14:33:57Z

1

IDataErrorInfo is the data validation mechanism for WPF. Don't you just love Microsoft's consistency? ;)

Implement IDataErrorInfo on your ViewModel like this:

public class MyViewModel : IDataErrorInfo
{
       public string Error
        {
            get { 
              return  GetErrorStringForThisViewModelInGeneral();
            }
        }

        public string this[string columnName]
        {
            get
            {
                string result = null;

                switch (columnName)
                {
                    case "Quantity":
                        if (Quantity <= 0)
                            result = "Quantity must be greater than 1.";
                    break;
                }
                return result;
            }

}

Inside of the property (aka this[]) validation, you could use the validator in the EnterpriseLibrary, a custom validator using Attributes, or anything you like. I am just showing a basic implementation to get you started.

edited Sep 8, 2011 at 14:33

answered Sep 8, 2011 at 14:27

Bahri Gungor

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3 Comments

Alberto Over a year ago

Sorry, I was referring to asynchronous validations - i.e Quantity is validated through a web service.

Bahri Gungor Over a year ago

To make the validation asynchronous, you should spin a thread to do the validation (to avoid hanging the application), then when the result returns do a NotifyPropertyChanged on the property being validated (e.g. Quantity). When the Notify happens, WPF will revalidate the field, and you should be able to set a condition so it doesn't revalidate remotely (as the value hasn't changed since the last validation).

Alberto Over a year ago

That's what I thought - shame it requires such a boilerplate code :(

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