how to edit select row in wpf

<Window x:Class="Wpf_grid.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="326" Width="946">
    <Grid>
        <DataGrid Name="MyDataGrid" Uid="MyDataGrid" AutoGenerateColumns="False" AlternationCount="2" SelectionMode="Single" Margin="0,31,0,0" >
            <DataGrid.Columns>
                <DataGridTextColumn Binding="{Binding Path=RegId}" IsReadOnly="True" Header="Registration Id" Width="sizeToHeader"/>
                <DataGridTextColumn Binding="{Binding Path=Name}" Header="Name" Width="sizeToHeader" />
                <DataGridTextColumn Binding="{Binding Path=FName}" Header="Father Name" Width="sizeToHeader" />
                <DataGridTextColumn Binding="{Binding Path=ContactNumber}" Header="Contact Number" Width="sizeToHeader" />
                <DataGridTextColumn Binding="{Binding Path=email}" Header="email" Width="sizeToHeader" />
                <DataGridTextColumn Binding="{Binding Path=password}" Header="password" Width="sizeToHeader" />
                <DataGridTextColumn Binding="{Binding Path=paddress}" Header="paddress" Width="sizeToHeader" />
                <DataGridTextColumn Binding="{Binding Path=pcity}" Header="pcity" Width="sizeToHeader" />
                <DataGridTextColumn Binding="{Binding Path=pstate}" Header="pstate" Width="sizeToHeader" />
                <DataGridTextColumn Binding="{Binding Path=ppinCode}" Header="ppinCode" Width="sizeToHeader" />
                <DataGridTextColumn Binding="{Binding Path=caddress}" Header="caddress" Width="sizeToHeader" />
                <DataGridTextColumn Binding="{Binding Path=ccity}" Header="ccity" Width="sizeToHeader" />
                <DataGridTextColumn Binding="{Binding Path=cstate}" Header="cstate" Width="sizeToHeader" />
                <DataGridTextColumn Binding="{Binding Path=cpinCode}" Header="cpinCode" Width="sizeToHeader" />
                <DataGridTemplateColumn Header="Edit Row">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Button Content="Edit" Click="btnEdit_Click"/>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
                <DataGridTemplateColumn Header="Delete Row">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Button Content="Delete" Click="btnDelete_Click"/>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
            </DataGrid.Columns>
        </DataGrid>
        
        <Button Content="LoadCustomer" Name="LoadCustomer" Height="23" HorizontalAlignment="Left" VerticalAlignment="Top" Width="75" Margin="0,5,0,0" Click="LoadCustomer_Click" />
    </Grid>
</Window>

private void btnEdit_Click(object sender, RoutedEventArgs e)
     {
         try
         {
             gridDataContext datacontext = new gridDataContext();
             registration registrationRow = MyDataGrid.SelectedValue as registration;
             int m = registrationRow.RegId;

             registration Registration = datacontext.registrations.Where(A => A.RegId == m).Single();
             Registration.Name = registrationRow.Name;
             Registration.FName = registrationRow.FName;
             datacontext.SubmitChanges();
             MessageBox.Show("Row Updated Successfully");
             LoadCustomerDetail();
         }
         catch (Exception ex)
         {
             MessageBox.Show(ex.Message);
             return;
         }
     }