Try the below
protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
{
foreach (GridViewRow row in GridView1.Rows)
{
string value = row.Cells[DesiredcolumnIndex].Text;
}
int i = e.NewEditIndex;
string value = GridView1.Rows[i].Cells[DesiredcolumnIndex].Text;
}