For Windows Phone Beginners

 Here is the code a simple sample for Windows Phone 8.1 login. Please user the following hard coded value for user name and password

UserName = "Tamil"
Pass Word = "Tamil"

Code used

<Grid>

        <TextBlock x:Name="userName1" HorizontalAlignment="Left" Height="40" Margin="45,91,0,0" TextWrapping="Wrap" FontSize="20" Text="User Name" VerticalAlignment="Top" Width="180"/>
        <TextBox x:Name="userName" HorizontalAlignment="Left" Height="43" Margin="45,130,0,0" TextWrapping="Wrap" FontSize="20" TextChanged="userName_TextChanged" Text="" VerticalAlignment="Top" Width="311"/>
        <TextBlock x:Name="passWord1"  HorizontalAlignment="Left" Height="34" Margin="45,228,0,0" TextWrapping="Wrap" FontSize="20" Text="Pass Word" VerticalAlignment="Top" Width="105"/>
        <TextBox x:Name="passWord" HorizontalAlignment="Left"  Height="43" Margin="45,262,0,0" TextWrapping="Wrap" FontSize="20" TextChanged="userName_TextChanged"  Text="" VerticalAlignment="Top" Width="311"/>
        <Button x:Name="exit" Content="Exit" HorizontalAlignment="Left" Height="54" Margin="45,355,0,0" VerticalAlignment="Top" Width="157" Click="Button_Click"/>
        <Button x:Name="login" Content="Login" HorizontalAlignment="Left" Height="26" Margin="202,355,0,0" VerticalAlignment="Top" Width="154" Click="Button_Click_1"/>
        <TextBlock x:Name="messageBlock" FontSize="35" HorizontalAlignment="Left" Height="120" Margin="45,468,0,0" TextWrapping="Wrap" Text="" VerticalAlignment="Top" Width="311"/>

    </Grid>

 private void Button_Click(object sender, RoutedEventArgs e)
        {
            this.login.Visibility = this.exit.Visibility = this.userName1.Visibility = this.userName.Visibility = this.passWord1.Visibility = this.passWord.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
            this.messageBlock.Text = "Thank you";
            this.messageBlock.Margin = new Thickness(0);
        }

        private void Button_Click_1(object sender, RoutedEventArgs e)
        {
            if(this.userName.Text =="Tamil" || this.passWord.Text =="Tamil")
            {
                 if(this.userName.Text =="Tamil" && this.passWord.Text =="Tamil")
                 {
                     this.login.Visibility = this.exit.Visibility = this.userName1.Visibility = this.userName.Visibility = this.passWord1.Visibility = this.passWord.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
                     this.messageBlock.Text = "Welcome to Enchanting Tamil Nadu";
                     this.messageBlock.Margin = new Thickness(0);
                 }
                 else if(this.userName.Text !="Tamil")
                 {
                     this.messageBlock.Text = "User is wrong";
                 }
                 else
                 {
                     this.messageBlock.Text = "Password is wrong";
                 }

            }
            else
            {
                this.messageBlock.Text = "UserName and Password are wrong";
            }
        }

        private void userName_TextChanged(object sender, TextChangedEventArgs e)
        {
            this.messageBlock.Text = string.Empty;
        }