Datagrid in WPF does not get refreshed

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C#

WPF

C#4.0

ASP.NET4

Hi,
I have created a WPF application. I have a textbox in which I give input which is saved to database on button click, adjacently I have a Datagrid present which will populate the data in database. Now when I add new data it gets stored in database but is not reflected on datagrid.
I guess I will have to refresh the datagrid so I used DataGrid.Items.Refresh() but this does not work for my application.
Plz help how to solve this issue.
Thanks

Code Snippet:

private void btnSubmit_Click(object sender, RoutedEventArgs e)
{
//Here is the code to save the data to XML
}

My datagrid gets bind as follows in wpf .xaml file :

<Window.Resources>
        <XmlDataProvider Source="C:\Output.xml"  
                         XPath="Data" x:Key="DataFile" />
    </Window.Resources>

<DataGrid AutoGenerateColumns="False" Height="177" HorizontalAlignment="Left" Margin="322,62,0,0" Name="dgData" VerticalAlignment="Top" Width="149" ItemsSource="{Binding Source={StaticResource DataFile},XPath=*}">
            <DataGrid.Columns>
                <DataGridTextColumn Header="Type" Binding="{Binding XPath=@Type}" />
                <DataGridTextColumn Header="Expense" Binding="{Binding XPath=@Value}" />
            </DataGrid.Columns>
        </DataGrid>

My XML looks as follows :

<Data>
   <Record>
     <Type>
       ABC
     </Type>
     <Expense>
       125
     </Expense>
   </Record>
   <Record>
     <Type>
       DEF
     </Type>
     <Expense>
       250
     </Expense>
   </Record>
</Data>

I just want to update the grid after the data is added to xml .