listview database bind not reflects back

Question

i have listview bounded to a database.i have textboxes to update data in table.

 

but when i enter data it updates on listview.

if i close and open the application sometimes data may be there and sometimes not,

when i checked my database table,the data not updated there

 

here's my xaml :

 

<Window x:Class="DatabaseApplication.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="554" Width="1134" Loaded="Window_Loaded" Background="White">
    <Grid  Background="White">

        <ListView Margin="8,9,738,284" Name="listView1" ItemsSource="{Binding}" MinWidth="250" MinHeight="100" IsSynchronizedWithCurrentItem="True">
            <ListView.View>
                <GridView>
                    <GridViewColumn Header="Item Number" DisplayMemberBinding="{Binding Path=ItemNumber}"></GridViewColumn>
                    <GridViewColumn Header="Item Name" DisplayMemberBinding="{Binding Path=ItemName}"></GridViewColumn>
                    <GridViewColumn Header="Item Price" DisplayMemberBinding="{Binding Path=ItemPrice}"></GridViewColumn>
                    <GridViewColumn Header="Margin" DisplayMemberBinding="{Binding Path=ItemMargin}"></GridViewColumn>
                    <GridViewColumn Header="Stock" DisplayMemberBinding="{Binding Path=ItemStock}"></GridViewColumn>
                </GridView>
            </ListView.View>
        </ListView>
        <TextBox Margin="92,238,738,252" Name="textBox1"  Height="23" DataContext="{Binding ElementName=listView1,Path=SelectedItem}" Text="{Binding Path=ItemName}" />
        <TextBox Height="23" Margin="92,0,738,224" Name="textBox2" VerticalAlignment="Bottom" DataContext="{Binding ElementName=listView1,Path=SelectedItem}" Text="{Binding Path=ItemPrice}" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="92,295,0,0" DataContext="{Binding ElementName=listView1,Path=SelectedItem}" Text="{Binding Path=ItemMargin}" Name="textBox3" VerticalAlignment="Top" Width="282" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="92,326,0,0" Name="textBox4" VerticalAlignment="Top" Width="282" DataContext="{Binding ElementName=listView1,Path=SelectedItem}" Text="{Binding Path=ItemStock}"/>


        <Label Margin="8,236,1026,254" Name="label1"  Height="23" >Item Name :</Label>
        <Label Height="23" Margin="8,0,1030,224" Name="label2" VerticalAlignment="Bottom">Item Price :</Label>
        <Label Content="Margin:" Height="25" HorizontalAlignment="Left" Margin="8,295,0,0" Name="label3" VerticalAlignment="Top" />
        <Label Content="Stock:" Height="28" HorizontalAlignment="Left" Margin="8,321,0,0" Name="label4" VerticalAlignment="Top" Width="61" />



        <Button Height="26" Margin="92,0,956,134" Name="btnAdd" VerticalAlignment="Bottom" Click="btnAdd_Click">Add</Button>
        <Button Height="26" Margin="234,0,0,134" Name="btnUpdate" VerticalAlignment="Bottom" Click="btnUpdate_Click" HorizontalAlignment="Left" Width="67">Update</Button>
        <Button Height="26" Margin="162,0,0,134" Name="btnDelete" VerticalAlignment="Bottom" Click="btnDelete_Click"  HorizontalAlignment="Left" Width="66" >Delete</Button>
        <Button Height="26" Margin="307,0,738,134" Name="btnClear" VerticalAlignment="Bottom" Click="btnClear_Click">Clear</Button>

    </Grid>


</Window>

here's my code:

 

using System.Data.SqlClient;
using System.Data;

namespace DatabaseApplication
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            ShowData();
        }
        private void btnAdd_Click(object sender, RoutedEventArgs e)
        {
            string itemname = textBox1.Text;
            string itemprice = textBox2.Text;
            string itemmargin = textBox1.Text;
            string itemstock = textBox2.Text;
            SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database1.mdf;Integrated Security=True;User Instance=True");
            con.Open();
            SqlCommand comm = new SqlCommand("insert into stock(ItemName,ItemPrice,ItemMargin,ItemStock) values(@itemname,@itemprice,@itemmargin,@itemstock)", con);
            comm.Parameters.AddWithValue("@itemname", textBox1.Text);
            comm.Parameters.AddWithValue("@itemprice", textBox2.Text);
            comm.Parameters.AddWithValue("@itemmargin", textBox3.Text);
            comm.Parameters.AddWithValue("@itemstock", textBox4.Text);
            comm.ExecuteNonQuery();
            con.Close();
            ShowData();
        }

        private void btnClear_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text = "";
            textBox2.Text = "";
            textBox3.Text = "";
            textBox4.Text = "";
        }
        public void ShowData()
        {
            SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database1.mdf;Integrated Security=True;User Instance=True");
            con.Open();
            SqlCommand comm = new SqlCommand("Select * from stock", con);
            DataTable dt = new DataTable();
            SqlDataAdapter da = new SqlDataAdapter(comm);
            da.Fill(dt);
            listView1.DataContext = dt.DefaultView;
        }

        private void btnDelete_Click(object sender, RoutedEventArgs e)
        {
            if (listView1.SelectedItems.Count > 0)
            {
                DataRowView drv = (DataRowView)listView1.SelectedItem;
                string id = drv.Row[0].ToString();
                SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database1.mdf;Integrated Security=True;User Instance=True");
                con.Open();
                SqlCommand comm = new SqlCommand("delete from stock where ItemNumber=@ItemNumber", con);
                comm.Parameters.AddWithValue("@ItemNumber", id);
                comm.ExecuteNonQuery();
                ShowData();
            }
        }

        private void btnUpdate_Click(object sender, RoutedEventArgs e)
        {
            if (listView1.SelectedItems.Count > 0)
            {
                DataRowView drv = (DataRowView)listView1.SelectedItem;
                string itemnumber = drv.Row[0].ToString();
                SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database1.mdf;Integrated Security=True;User Instance=True");
                con.Open();
                SqlCommand comm = new SqlCommand("update stock  set ItemName=@itemname,ItemPrice=@itemprice,ItemMargin=@itemmargin,ItemStock=@itemstock where ItemNumber=@itemnumber", con);
                comm.Parameters.AddWithValue("@itemnumber",itemnumber );
                comm.Parameters.AddWithValue("@itemname", textBox1.Text);
                comm.Parameters.AddWithValue("@itemprice", textBox2.Text);
                comm.Parameters.AddWithValue("@itemmargin",textBox3.Text);
                comm.Parameters.AddWithValue("@itemstock",textBox4.Text);
                comm.ExecuteNonQuery();
                con.Close();
                ShowData();
            }

        }


    }
}

 please give me a solution