DropDownList所选项目始终是列表中的第一项 [英] DropDownList selected item always first item in list

问题描述

我在用户控件中有一个DropDownList；但是，无论我做什么，我都无法正确填充任何选定"属性(SelectedItem，SelectedIndex，SelectedValue).无论实际上选择了哪个项目，这三个属性的值都是我列表中的第一项.

I have a DropDownList in a user control; however, no matter what I do I can't get any of the "selected" properties (SelectedItem, SelectedIndex, SelectedValue) to populate correctly. The value of all three of these properties is the first item in my list no matter which item was actually selected.

<asp:DropDownList ID="ParticipantsSelectList" runat="server">
    <asp:ListItem Value="">Please select a team...</asp:ListItem>
    <asp:ListItem value="{D37EFA0C-988A-4A2A-8D6E-80E3BAE00DEE}">Blue Team</asp:ListItem>
    <asp:ListItem value="{7543E282-C9B8-435A-86A2-70E8E3BB38E5}">Green Team</asp:ListItem>
    <asp:ListItem value="{F6BEF34A-215E-4179-9F4C-68F7C43D755F}">Orange Team</asp:ListItem>
    <asp:ListItem value="{D50AD44A-686A-4BD3-B62E-D70ABF153AE5}">Red Team</asp:ListItem>
    <asp:ListItem value="{DEFB7DA6-B0FF-4C36-A015-F3E8BC7AECA2}">Yellow Team</asp:ListItem>
    <asp:ListItem value="{D37EFA0C-988A-4A2A-8D6E-80E3BAE00DEE},{7543E282-C9B8-435A-86A2-70E8E3BB38E5},{F6BEF34A-215E-4179-9F4C-68F7C43D755F},{D50AD44A-686A-4BD3-B62E-D70ABF153AE5},{DEFB7DA6-B0FF-4C36-A015-F3E8BC7AECA2}">All Teams</asp:ListItem>
</asp:DropDownList>
<asp:Button runat="server" Text="Submit" />

---

private void Page_Load(object sender, EventArgs e)
{
    if (!String.IsNullOrEmpty(ParticipantsSelectList.SelectedValue)) // SelectedValue is always empty string (value of the first item in the list)
    {
        resultsPanel.Visible = true;
        selectTeamLabel.Visible = false;
        GenerateResultsTable();
    }
    else
    {
        resultsPanel.Visible = false;
        selectTeamLabel.Visible = true;
    }
}

推荐答案

尝试在 Page_Load

private void Page_Load(object sender, EventArgs e)
{

    if (!Page.IsPostBack)
    { 
        //Your Code....
    }
}

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