Data Input Validation In WPF: Validation With Exception

Introduction to Validation with Exception

Validating from exceptions is one of the simplest validation mechanisms for WPF. Normally the binding of catch exceptions are thrown by get/set blocks of bound properties. This mechanism will throw an exception when we get incorrect data.

ValidatesOnExceptions will indicate the error on the control if a get/set block throws an exception.

Demo

http://www.c-sharpcorner.com/UploadFile/91c28d/data-input-validation-in-wpf-part-1-validation-with-except/Images/WPF.jpg

We have two TextBoxes for account number and Zip code, you can see ValidatesOnExceptions=True in the Zip code binding.

public partial  class ValidationWithException : UserControl, INotifyPropertyChanged  
    {  
        public ValidationWithException()  
        {  
            InitializeComponent();  
        }  
        #region INotifyPropertyChanged Members  
   
        public event  PropertyChangedEventHandler PropertyChanged;  
        public void  OnPropertyChanged(string txt)  
        {  
   
            PropertyChangedEventHandler handle = PropertyChanged;  
            if (handle != null)  
            {  
                handle(this, new  PropertyChangedEventArgs(txt));  
            }  
        }  
        #endregion  
        private int  accountNumber;  
   
        public int  AccountNumber  
        {  
            get { return accountNumber; }  
            set { accountNumber = value; }  
        }  
   
        private string  zipCode;  
   
        public string  ZipCode  
        {  
            get { return zipCode; }  
            set {  
                if (zipCode != value)  
                {  
                    ValidateZipCode(value);  
                    zipCode = value;  
                    OnPropertyChanged("ZipCode");  
                }  
               
            }  
        }  
        private void  ValidateZipCode(string value)  
        {  
            if (!string.IsNullOrEmpty(value) && value.Length < 5)  
            {  
                throw new  ArgumentException("Invalid Zip Code");  
            }  
        }  
           
    }

In the class file we have one method, validateZipCode, that will check the length of the Zip code. If the Zip code length is less than 5 then it will throw an ArgumentException. We will call this method before setting the Zip code value in the set block. One of the advantages of using this is you can prevent an incorrect value before setting.

Run the application. Type something such as a Zip code and press the Tab key.

http://www.c-sharpcorner.com/UploadFile/91c28d/data-input-validation-in-wpf-part-1-validation-with-except/Images/WPF1.jpg
Now you can see the Red box on the control. WPF controls have a built-in error template that simply puts a Red box around the control.

See Also

How to: Implement Binding Validation
INotifyDataErrorInfo Interface