Deleting An item from a List Box from a Database

Hi Im trying to delete an item from the listbox which the user selects here you can find my code and a screenshot tnx.

Code:

public void deleteEvent(ListBox list_event)
{
    int i = list_event.SelectedIndex;

    ds.Tables["tblEvents"].Rows[i].Delete();
    da.Update(ds.Tables["tblEvents"]);
}

Im getting开发者_StackOverflow Object reference not set to an instance of an object Exception.

ScreenShot:

• Make sure ds is not null.
• Make sure there is a table called tblEvents in the data set, ds.
• Make sure the number of rows in the tblEvents is large enough so that the index you're using when deleting fits within the number of rows.
• Make sure that the data adapter da is not null.

Without any further information, it's close to impossible to give any more insights.