try this
protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
GridViewRow row = (GridViewRow)GridView1.Rows[e.RowIndex];
string id = GridView1.DataKeys[e.RowIndex].Values[0].ToString();
string ddluserType = ((DropDownList)row.FindControl("ddlStatus")).SelectedValue;
SqlCommand cmdUpdate = new SqlCommand("Update Orders set OStatus = '" + ddluserType + "' where OID='" + id + "'", con);
cmdUpdate.ExecuteNonQuery();
con.Close();
GridView1.EditIndex = -1;
databind();
}