C# 使用AppendDataBoundItems时，我的2个GridView中的1个视图中存在重复数据

我有两个gridview，分别称为DDLTOC和DDLCase。我使用appenddatabounditems将默认值插入DDL。我的默认值是（“选择成员报告ID”）

我还在DDLTOC上添加了另一个绑定

protected void DDLTOC_SelectedIndexChanged(object sender, EventArgs e)
    {
        using (var connAdd = new SqlConnection("Data Source = localhost; Initial Catalog = project; Integrated Security= SSPI"))
        {
            connAdd.Open();

            var sql = "SELECT memberreportid FROM MemberReport Where typeofcrime ='" + DDLTOC.SelectedValue + "' AND caseprogress='settled'";
            using (var cmdAdd = new SqlDataAdapter(sql, connAdd))
            {
                DataSet ds2 = new DataSet();
                cmdAdd.Fill(ds2);

                DDLCase.DataSource = ds2;
                DDLCase.DataTextField = "memberreportid";
                DDLCase.DataValueField = "memberreportid";
                DDLCase.DataBind();

            }

            sql = "Select username, memberreportid, location, crdatetime, citizenreport, image1, image2, image3, image4, image5 from MemberReport where typeofcrime ='" + DDLTOC.SelectedItem.Text + "' and handle='handled'";
            using (var cmdAdd = new SqlDataAdapter(sql, connAdd))
            {
                DataSet dsSel = new DataSet();
                cmdAdd.Fill(dsSel);
                GVCR.DataSource = dsSel;
                GVCR.DataBind();
            }

            connAdd.Close();
        }


    }

DDLTOC_SelectedIndex中的第一个绑定基本上允许根据DDLTOC中选择的值在dropdownlist上显示DDLCase的值。第二个绑定将在gridview中显示数据库中的必要值。我有2个数据库值，将显示在DDLTOC、帮派和抢劫中。因此，如果我随机选择组，然后选择返回默认值，然后选择组，再返回选择默认值，它将在我的DDLCase上显示两次组的DDLCase值

---

为什么会出现重复数据

在数据绑定之前，只需清除其项集合。将数据绑定代码部分修改为：

DDLCase.Items.Clear();
DDLCase.DataSource = ds2;
DDLCase.DataTextField = "memberreportid";
DDLCase.DataValueField = "memberreportid";
DDLCase.DataBind();
DDLCase.Items.Insert(0, new ListItem("Select Case", ""));
DDLCase.SelectedIndex = 0;

---

或者，您可以在

DDLCase

标记中设置

EnableViewState=“False”

但是在这种情况下，如果页面上发生任何其他回发（而不是

ddlcose

，比如从一个不再填充

DDLCase

的按钮），则

DDLCase

的数据将丢失。它是

DDLCase

的

ViewState

，它保持了它以前的状态，以便在交叉请求中下拉项不会丢失。除非其ViewState被禁用，否则您只是将其添加到其项目集合中。

如果我要插入项目。清除（）；在数据绑定之前，当我选择DDLTOC值时，DDLCase中的默认值将消失。如果我没记错的话，ASP.Net有一个错误，第一个选项无法选择。我尝试启用视图状态，当我在DDLTOC中选择一个选项时，它将仅显示我的默认值

DDLCase

的默认值是什么？您可以清除项目集合，然后进行数据绑定，然后使用

items.InsertAt（0）

插入该值；然后可以使用

SelectedIndex=0

作为要选择的默认值。你能发布

DDLCase

的标记吗？

protected void Page_Load(object sender, EventArgs e)
    {
        if (Page.IsPostBack == false)
        {
            SqlConnection conn = new SqlConnection("Data Source=localhost;" +
                "Initial Catalog=project; Integrated Security = SSPI");

            SqlDataAdapter da = new SqlDataAdapter("SELECT distinct typeofcrime FROM MemberReport where handle='handled' AND caseprogress='settled'", conn);
            conn.Open();

            DataSet ds = new DataSet();
            da.Fill(ds);

            DDLTOC.DataSource = ds;
            DDLTOC.DataTextField = "typeofcrime";
            DDLTOC.DataValueField = "typeofcrime";
            DDLTOC.DataBind();                   

            conn.Close();

        }

    }

protected void DDLTOC_SelectedIndexChanged(object sender, EventArgs e)
    {
        using (var connAdd = new SqlConnection("Data Source = localhost; Initial Catalog = project; Integrated Security= SSPI"))
        {
            connAdd.Open();

            var sql = "SELECT memberreportid FROM MemberReport Where typeofcrime ='" + DDLTOC.SelectedValue + "' AND caseprogress='settled'";
            using (var cmdAdd = new SqlDataAdapter(sql, connAdd))
            {
                DataSet ds2 = new DataSet();
                cmdAdd.Fill(ds2);

                DDLCase.DataSource = ds2;
                DDLCase.DataTextField = "memberreportid";
                DDLCase.DataValueField = "memberreportid";
                DDLCase.DataBind();

            }

            sql = "Select username, memberreportid, location, crdatetime, citizenreport, image1, image2, image3, image4, image5 from MemberReport where typeofcrime ='" + DDLTOC.SelectedItem.Text + "' and handle='handled'";
            using (var cmdAdd = new SqlDataAdapter(sql, connAdd))
            {
                DataSet dsSel = new DataSet();
                cmdAdd.Fill(dsSel);
                GVCR.DataSource = dsSel;
                GVCR.DataBind();
            }

            connAdd.Close();
        }


    }

DDLCase.Items.Clear();
DDLCase.DataSource = ds2;
DDLCase.DataTextField = "memberreportid";
DDLCase.DataValueField = "memberreportid";
DDLCase.DataBind();
DDLCase.Items.Insert(0, new ListItem("Select Case", ""));
DDLCase.SelectedIndex = 0;