Creating new instance

Hi, I am very new to C#, and have an error on click of the save button. I have created a simple WPF application using Visual Studio, and have a SQL databased linked in. I have 3 buttons on the page, one to go to the next record, one to nacigate to the previous, and one to save.

CollectionViewSource tblOrdersViewSource = null;
PO2DataSet PO2DataSet = null;
PO2DataSetTableAdapters.TblOrdersTableAdapter pO2DataSetTblOrdersTableAdapter;

private void Window_Loaded(object sender, RoutedEventArgs e)

WPFPurchaseOrders.PO2DataSet pO2DataSet = ((WPFPurchaseOrders.PO2DataSet)(this.FindResource("pO2DataSet")));
// Load data into the table TblOrders. You can modify this code as needed.
pO2DataSetTblOrdersTableAdapter = new WPFPurchaseOrders.PO2DataSetTableAdapters.TblOrdersTableAdapter();
tblOrdersViewSource = ((System.Windows.Data.CollectionViewSource)(this.FindResource("tblOrdersViewSource")));
// Load data into the table TblItem. You can modify this code as needed.
WPFPurchaseOrders.PO2DataSetTableAdapters.TblItemTableAdapter pO2DataSetTblItemTableAdapter = new WPFPurchaseOrders.PO2DataSetTableAdapters.TblItemTableAdapter();
System.Windows.Data.CollectionViewSource tblOrdersTblItemViewSource = ((System.Windows.Data.CollectionViewSource)(this.FindResource("tblOrdersTblItemViewSource")));

private void previousButton_Click(object sender, RoutedEventArgs e)

private void nextButton_Click(object sender, RoutedEventArgs e)

private void saveButton_Click(object sender, RoutedEventArgs e)
if (pO2DataSetTblOrdersTableAdapter.Update PO2DataSet.TblOrders) > 0)
MessageBox.Show("Changes were saved");
MessageBox.Show("No changes were made or saved");

The error is on the first line of the if statement. The error message 'NullReferenceException was unhandled'. When reading the troubleshooting tips it mentions creating a instance for the class, but I thought this was already done at the top of the code?

Any suggestions/explinations is much appriciated.

Many thanks.
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