dropdown box populate all values in datagridview r selected

This is what I've got so far. I am receiving errors however on what is highlighted in yellow.

 private void button1_Click(object sender, EventArgs e)
        {
            foreach (var c in advancedDataGridView1.SelectedCells)
            {
                db_reconDataSet.Rows[c.RowIndex][c.ColumnIndex] = c.Value;
            }

            advancedDataGridView1.DataSource = db_reconDataSet;
        }

how do I get the row number for the of the selected rows of datagridview?

So when ever some one presses the button "Update Selected Datagridview" I want the value of "Mike" to replace the highlighted blue values in the datagridview. Is that possible?

 

so how do we send values selected from dropdown box into selected  (highlighted)datagridview?