Asp.NET DropDownList的复位的SelectedIndex回发后 [英] Asp.NET DropDownList Resets SelectedIndex after PostBack

问题描述

做了很多研究联机后，我仍然被这个问题难住了。我有一个加载类的名称和数量成下拉列表的页面。我只能这样做，如果！（Page.IsPostBack）。当的AutoPostBack 触发的SelectedIndex = 0 。我已经尝试了几种不同的东西。这里是我的code：

After doing a lot of research online I'm still stumped by this problem. I have a page that loads the names and count of categories into a drop down list. I only do this if !(Page.IsPostBack). When AutoPostBack fires the SelectedIndex = 0. I've tried several different things. Here is my code:

页

<form id="AddAssignmentForm" runat="server">
<asp:ScriptManager ID="ScriptManager1" EnablePartialRendering="true" runat="server" />

<asp:UpdatePanel ID="CommentUpdate" runat="server">
<ContentTemplate>

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<asp:DropDownList ID="ddlCategory" runat="server" Width="206" OnSelectedIndexChanged="ddlCategory_SelectedIndexChanged" AutoPostBack="true" />
<asp:TextBox ID="txtName" runat="server" Width="200" />
<asp:TextBox ID="txtAbbrv" runat="server" Width="200" />
<asp:TextBox ID="txtDescription" runat="server" Width="200" Height="90" TextMode="MultiLine" />

</ContentTemplate>
</asp:UpdatePanel>
</form>

下面是后端code。

private void Page_Load(object sender, System.EventArgs e)
{
    if (!Page.IsPostBack)
    {
        GetCategories();
    }
}

public void GetCategories()
{
    String strSql = @"SELECT Name, Total
                        FROM MyTable";

    if (con.State == ConnectionState.Closed)
        con.Open();

    OleDbCommand cmdsql = new OleDbCommand(strSql, con);
    OleDbDataReader cmdReader = cmdsql.ExecuteReader();

    if (cmdReader.HasRows)
    {
        while (cmdReader.Read())
        {
            ddlCategory.Items.Add(new ListItem(cmdReader["Category_Name"].ToString(), cmdReader["Total"].ToString()));

        }
        ddlCategory.SelectedIndex = -1;
    }


    cmdReader.Close();
    con.Close();
}

public void FillForm(int index)
{
    ListItem item = ddlCategory.Items[index];
    txtName.Text = item.Text + " " + (Convert.ToInt32(item.Value) + 1).ToString();
    txtAbbrv.Text = item.Text.Substring(0, 1) + (Convert.ToInt32(item.Value) + 1).ToString();
}

public void ddlCategory_SelectedIndexChanged(Object sender, EventArgs e)
{
    //When I break here SelectedIndex always = 1.
    FillForm(ddlCategory.SelectedIndex);
}

我只是希望能够填充基于选择的指数的形式，但我似乎无法得到正确的答案。任何帮助是AP preciated。

I just want to be able to populate the form based on the selected index, but I can't seem to get the correct answer. Any help is appreciated.

推荐答案

我发现了这个问题。从我的SQL语句正在填充值包含了重复的值。出于某种原因，这是导致这使得它让每一个我选择了一个列表项时整个名单将重置奇怪的方式发生故障整个事情。通过确保没有重复的值，在code开始工作完美。感谢大家的帮助。

I discovered the problem. The values being populated from my SQL statement contained values that repeated. For some reason this was causing the entire thing to malfunction in weird ways which made it so that every time I selected a ListItem the whole list would reset. By making sure no values repeated, the code started working perfectly. Thanks for everyone's help.

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