How do I get a DataRow from a row in a DataGridView

DataRow row = ((DataRowView)DataGridViewRow.DataBoundItem).Row

Assuming you've bound an ordinary DataTable.

MyTypedDataRow row = (MyTypedDataRow)((DataRowView)DataGridViewRow.DataBoundItem).Row

Assuming you've bound a typed datatable.

See the article on MSDN for more information.

DataTable table = grdMyGrid.DataSource as DataTable;
DataRow row = table.NewRow();
row = ((DataRowView)grdMyGrid.SelectedRows[0].DataBoundItem).Row;