Asp.net的DropDownList的IsPostBack是alwasy假 [英] Asp.net DropDownList isPostBack is alwasy false

问题描述

我是新来的ASP和我遇到，我一直在一整天的问题！即时通讯使用的是和我回发不断返回false，因此我的SelectedIndexChanged方法从来没有得到机会运行！

I'm new to ASP and I've come across a problem that I've been at all day! im using a and my postback is constantly returning false, thus my selectedIndexChanged method never gets a chance to run!

下面是我的code：

    <table border="1">
    <tr>
        <th>
            Build version:
        </th>
        <th>
            <%-- Html.DropDownList("Builds", null, new {@onchange = "onChange(this.value);" }) --%>
            <%-- Html.DropDownList("BuildID", (SelectList) ViewBag.Builds, "--Select One--") --%>
            <%-- Html.DropDownList("BuildDD", (IEnumerable<SelectListItem>)ViewBag.Builds, "--Select One--") --%>

            <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="false" 
                DataSourceID="SqlDataSource1" DataTextField="Version" 
                onselectedindexchanged="DropDownList1_SelectedIndexChanged" 
                onprerender="DropDownList1_PreRender" onload="DropDownList1_Load">
            </asp:DropDownList>
            <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
                ConnectionString="<%$ ConnectionStrings:DAContext %>" 
                SelectCommand="SELECT [Version] FROM [Builds]" >
                </asp:SqlDataSource>
        </th>
        <th>
            <asp:Label ID="Label1" runat="server" Text= "--Build Version--"></asp:Label>
        </th>
    </tr>
</table>

和我的背后code（这是在同一个aspx文件作为DropDownList的，不知道如果多数民众赞成好吧）

and my code behind (it's in the same aspx file as the dropdownlist, not sure if thats alright)

<script runat="server">

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
    Response.Write((sender as DropDownList).SelectedItem.Text);
    Label1.Text = DropDownList1.SelectedItem.Text;


}

protected void DropDownList1_PreRender(object sender, EventArgs e)
{
    base.OnPreInit(e);
    DropDownList1.SelectedIndexChanged += new EventHandler(DropDownList1_SelectedIndexChanged);
}

protected void DropDownList1_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        Response.Write("Post Back is False");
        DropDownList1.Items.Clear();
        DropDownList1.DataSourceID = "SqlDataSource1";
        DropDownList1.DataTextField = "Version";
        DropDownList1.DataBind();
    }
}

任何帮助将是AP preciated！ IM pretty卡住而无法得到更进一步没有帮助！谢谢！

Any help would be appreciated! im pretty stuck and can't get much further without help! thanks!!

推荐答案

在您的下拉列表中设置的AutoPostBack =真正的

set AutoPostBack="true" in your dropdown list

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