“DropDownList1”有一个无效 SelectedValue，因为它不在项目列表中。
2个表table1,table2
table1列：id,name        
table2列：id,name,sort1 //table1的name=table2的sort1

DropDownList1绑定table1
GridView1绑定table2
点修改，DropDownList1显示相应的 一级分类

protected void Page_Load(object sender, EventArgs e)

    {

        if (!IsPostBack)

        {

            SqlConnection conn = new SqlConnection(ConnectionString);

            string sql = "select * from table1";

            SqlDataAdapter da = new SqlDataAdapter(sql, conn);

            DataSet ds = new DataSet();

            da.Fill(ds);



            DropDownList1.DataSource = ds;

            DropDownList1.DataTextField = "name";

            DropDownList1.DataValueField = "name";

            DropDownList1.DataBind();



            string sql2 = "select * from table2";

            SqlDataAdapter da2 = new SqlDataAdapter(sql2, conn);

            DataSet ds2 = new DataSet();

            da2.Fill(ds2);

            GridView1.DataSource = ds2;

            GridView1.DataBind();

        }

    }

    protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)

    {

        int index = int.Parse(e.CommandArgument.ToString());

        int id = int.Parse(this.GridView1.DataKeys[index].Value.ToString());

        if (e.CommandName == "Edit")

        {

            SqlConnection conn = new SqlConnection(ConnectionString);

            string sql = "select * from table2 where id=" + id + "";

            SqlDataAdapter da = new SqlDataAdapter(sql, conn);

            DataSet ds = new DataSet();

            da.Fill(ds);

      &nbs