How To Save Data From DataGridView bound to one datasource to aTableadapter

I have a dataGridView that is bound to a DataTable and I am trying to save the data to a TableAdapter.

This is a VS 2008 C# Windows Application.

I know that I am casting this correctly as I am raising the following error:
Unable to cast object of type 'System.Windows.Forms.BindingSource' to type 'MFG_CAPTURE_DATADataTable'.

Here is the call that is raising the error:
myST_BLL.captureDataTableAdapter().Update((dsStagingTables.MFG_CAPTURE_DATADataTable)dvgDataCapture.DataSource);

Here is the method itself in the myST_BLL class:
static private MFG_CAPTURE_DATATableAdapter _captureDataTableAdapter;

public MFG_CAPTURE_DATATableAdapter captureDataTableAdapter()
{
if (_captureDataTableAdapter == null)
{
_captureDataTableAdapter = new MFG_CAPTURE_DATATableAdapter();
_captureDataTableAdapter.Connection.ConnectionString = _connStr;
}
return _captureDataTableAdapter;
}

The DataTable is one that I have created by combining two tables but the format is identical to the table that the MFG_CAPTURE_DATATableAdapter is connected to.

Can someone give me a little guidance please?

Thank you