DataGridView.BSource.Filter error w/ db update

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C#

DataGridView

Hi,

I am writing a C# app using a DataGridView bound to a MySQL database. Nothing too unusual, except that I wanted the users to be able to edit data directly in the DGV. To make this work, I used this link as a guide:
Auto Saving DataGridView Rows to a SQL Server Database[^]

I added a right-click context menu to the DGV with some hard-coded filters (Users can't customize). When I filter on one criteria, it works...then I (with another menu) reset it, and that works, but whether I reset it or not, the second time I try to filter on different criteria, I get a null reference exception (see code below).

I understand why it's happening. I am just not sure the best way to fix it. Any help would be appreciated!

	  private void bSource_PositionChanged(object sender, EventArgs e)
	  {
		 bSource.EndEdit();
		 // if the user moves to a new row, check if the last row was changed
		 BindingSource thisBindingSource = (BindingSource)sender;
		 DataRow ThisDataRow = ((DataRowView)thisBindingSource.Current).Row; // <- This is where it breaks
		 if (ThisDataRow == LastDataRow)
		 {
			// we need to avoid writing a datarow to the database when it is still processing. Otherwise
			// we get a problem with the event handling of the DataTable.
			return;
		 }
		 UpdateRowToDatabase();
		 // track the current row for next PositionChanged event
		 LastDataRow = ThisDataRow;
	  }

/* Example for two of the context menu buttons */
	  private void toolStripMenu_40hour_Click(object sender, EventArgs e)
	  {
		 bSource.Filter = "colHours = 40";
	  }
	  private void toolStripMenu_Overtime_Click(object sender, EventArgs e)
	  {
		 bSource.Filter = "colHours = 0 OR colHours > 40";
	  }
	  private void toolStripMenu_Reset_Click(object sender, EventArgs e)
	  {
		 bSource.RemoveFilter();
	  }