GridView中实现DropDownList联动

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;

public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }
    protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        //如果是数据绑定行
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            DropDownList ddlParent = (DropDownList)e.Row.FindControl("ddlParent");
            GetParent(ddlParent);
        }
    }


    private void GetParent(DropDownList ddl)
    {
        string sql = "select * from Models where ParentModuleID=0";
        DataTable dt = DB.CreateDT(sql);
        ddl.DataTextField = "ModuleName";
        ddl.DataValueField = "ID";
        ddl.DataSource = dt;
        ddl.DataBind();
    }
    protected void ddlParent_SelectedIndexChanged(object sender, EventArgs e)
    {
        GridViewRow row = (GridViewRow)((sender) as Control).NamingContainer;
        DropDownList ddlParent = (sender) as DropDownList;

        int ddlParentID=Convert.ToInt32(ddlParent.SelectedValue);

        DropDownList ddlChildren = row.FindControl("ddlChildren") as DropDownList;
        GetChildren(ddlChildren,ddlParentID);
        
    }

    private void GetChildren(DropDownList ddl, int parentID)
    {
        string sql = "select * from Models where ParentModuleID=" + parentID + "";
        DataTable dt = DB.CreateDT(sql);
        ddl.DataTextField = "ModuleName";
        ddl.DataValueField = "ID";
        ddl.DataSource = dt;
        ddl.DataBind();
    }
}