Silverlight Validation Using INotifyPropertyChanged

If we want to perform validation in silverlight we have to use INotifyPropertyChanged interface which notifies clients that a property value has changed.

Create a user class and implement INotifyPropertyChanged interface.

public class User : INotifyPropertyChanged

{

        //Delegate.

        public event PropertyChangedEventHandler PropertyChanged;

        //Username.

        private string userName;

        public string UserName

        {

            get { return userName; }

            set

            {

                //Validate the username for 6 chars.

                if (value.Length < 6)

                {

                    throw new ArgumentException("User Name should contain atleast 6 chars");

                }

                userName = value;

                RaisePropertyChanged("UserName");

            }

        }

        //Password.

        private string password;

        public string Password

        {

            get { return password; }

            set

            {

                //Validate the password for 6 chars.

                if (value.Length < 6)

                {

                    throw new ArgumentException("Password should contain atleast 6 chars");

                }

                password = value;

                RaisePropertyChanged("Password");

            }

        }

        //Occurs when a property value changes.

        private void RaisePropertyChanged(string propertyName)

        {

            if (this.PropertyChanged != null)

            {

                this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));

            }

        }

}

In Login.xaml page:-

<Grid x:Name="LayoutRoot">

        <Grid.RowDefinitions>

            <RowDefinition Height="30"></RowDefinition>

            <RowDefinition Height="30"></RowDefinition>

            <RowDefinition Height="30"></RowDefinition>

        </Grid.RowDefinitions>

        <Grid Grid.Row="0">

            <Grid.ColumnDefinitions>

                <ColumnDefinition Width="250"></ColumnDefinition>

                <ColumnDefinition Width="100"></ColumnDefinition>

            </Grid.ColumnDefinitions>

            <sdk:Label Height="28" Grid.Column="0" HorizontalAlignment="Left"  Name="lblUserName" Content="Enter User Name:" VerticalAlignment="Top" Width="100"/>

            <TextBox Grid.Column="0"  HorizontalAlignment="Right"  Name="txtUserName" VerticalAlignment="Top" Width="150">

                <TextBox.Text>

                    <!--Binding should be twoway-->

                    <Binding Mode="TwoWay" Path="UserName" NotifyOnValidationError="True" ValidatesOnExceptions="True"/>

                </TextBox.Text>

            </TextBox>

        </Grid>

        <Grid Grid.Row="1">

            <Grid.ColumnDefinitions>

                <ColumnDefinition Width="250"></ColumnDefinition>

                <ColumnDefinition Width="100"></ColumnDefinition>

            </Grid.ColumnDefinitions>

            <sdk:Label Height="28" Grid.Column="0" HorizontalAlignment="Left"  Name="lblPassword" Content="Enter Password:" VerticalAlignment="Top" Width="100"/>

            <TextBox Grid.Column="0"  HorizontalAlignment="Right"  Name="txtPassword" VerticalAlignment="Top" Width="150">

                <TextBox.Text>

                    <!--Binding should be twoway-->

                    <Binding Mode="TwoWay" Path="Password" NotifyOnValidationError="True" ValidatesOnExceptions="True"/>

                </TextBox.Text>

            </TextBox>

        </Grid>

        <Button Grid.Row="2" Content="Login" Height="23" HorizontalAlignment="Left" Name="btnLogin" VerticalAlignment="Top" Width="75" />

    </Grid>

In constructor:-

public partial class Login: UserControl

    {

        public Login()

        {

            InitializeComponent();

            //User object.

            User objUser = new User();

            LayoutRoot.DataContext = objUser;

        }

    }

Run the appliction without debugging.

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