DDL row bound in gridview

protected void RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow && gvProduct.EditIndex == e.Row.RowIndex)
    {
        DropDownList product_size= (DropDownList)e.Row.FindControl("ddlproduct_size");
        string query = "select distinct product_size from product";
        SqlCommand cmd = new SqlCommand(query);
        ddlCities.DataSource = GetData(cmd);
        ddlCities.DataTextField = "product_size";
        ddlCities.DataValueField = "product_size";
        ddlCities.DataBind();
        ddlCities.Items.FindByValue((e.Row.FindControl("lblproduct_size") as Label).Text).Selected = true;
    }
}