<!--LayoutRoot is the root grid where all page content is placed-->

    <Grid x:Name="LayoutRoot" Background="Transparent">

        <Grid.RowDefinitions>

            <RowDefinition Height="Auto"/>

            <RowDefinition Height="*"/>

        </Grid.RowDefinitions>

        <!--TitlePanel contains the name of the application and page title-->

        <StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">

            <TextBlock x:Name="ApplicationTitle" Text="My Application  " Style="{StaticResource PhoneTextNormalStyle}"/>

            <TextBlock x:Name="PageTitle" Text="Textbox Demo" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>

        </StackPanel>

        <!--ContentPanel - place additional content here-->

        <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">

            <TextBlock Height="42" HorizontalAlignment="Left" Margin="30,6,0,0" Name="lblEmpDetails" Text="Employee Details" VerticalAlignment="Top" Width="366" DataContext="{Binding}" FontSize="32" />

            <TextBlock Height="50" HorizontalAlignment="Left" Margin="30,75,0,0" Name="lblName" Text="Emp Name" VerticalAlignment="Top" Width="165" FontSize="28" />

            <TextBox Height="72" HorizontalAlignment="Left" Margin="191,63,0,475" Name="txtName" Text="" VerticalAlignment="Center" Width="230" />

            <TextBlock Height="60" HorizontalAlignment="Left" Margin="35,163,0,0" Name="lblAddress" Text="Address" VerticalAlignment="Top" Width="118" FontSize="28" />

            <TextBox Height="72" HorizontalAlignment="Left" Margin="192,150,0,0" Name="txtAddress" Text="" VerticalAlignment="Top" Width="230" />

            <TextBlock Height="44" HorizontalAlignment="Left" Margin="36,247,0,0" Name="lblMobNo" Text="Mobile No." VerticalAlignment="Top" Width="144" FontSize="28" />

            <TextBox Height="72" HorizontalAlignment="Left" Margin="192,235,0,0" Name="txtMobNo" Text="" VerticalAlignment="Top" Width="229" />

            <Button Content="Submit" Height="72" HorizontalAlignment="Left" Margin="176,344,0,0" Name="btnSubmit" VerticalAlignment="Top" Width="160" Click="btnSubmit_Click" />

        </Grid>

    </Grid>

using System.Windows;

using Microsoft.Phone.Controls;

namespace textBoxDemo

{

    public partial class MainPage : PhoneApplicationPage

    {

        // Constructor

        public MainPage()

        {

            InitializeComponent();

        }

        private void btnSubmit_Click(object sender, RoutedEventArgs e)

        {

            if (txtName.Text.Equals(string.Empty) || txtAddress.Text.Equals(string.Empty) || txtMobNo.Text.Equals(string.Empty))

                MessageBox.Show("Please fill all enteries");

            else

            MessageBox.Show("Data Successfull Submitted");

        }

    }

}