SelectetValue不返回ASP.NET DropDownList中的选定值

Question

I'm slowly going mad over the following problem: In my ASP.NET page (target: .NET 4.0) I have the following declaration of a DropDownList :

<asp:DropDownList ID="cmbRequestState" runat="server" EnableViewState="true">
    <asp:ListItem Text="Pending" Value="0"></asp:ListItem>
    <asp:ListItem Text="Open" Value="1"></asp:ListItem>
    <asp:ListItem Text="Closed" Value="2"></asp:ListItem>
</asp:DropDownList> 

In the Page_Load event in code-behind I set the cmbRequestState value to "2" for example - everything's fine, the value shown in the combo box in the browser is "Closed", as the respective <option> tag in HTML has the selected="selected" attribute.

Then I select "Open" and perform a postback using a "Save"-button on my page. When I retrieve the SelectedValue for cmbRequestState in the button's code, it is still "2" even though I've selected "1".

Now I don't write ASP.NET applications too often, but I do have some knowledge in HTML and PHP programming and from my WinForms and WPF background I'd expect the SelectedValue to contain the value that is currently selected... Also, I do not want to perform a postback every time a user selects a value from the list.

What am I missing here? How would I make sure that when opening the page, the current request state is selected and still get the new selection if the user makes a change?

Answer 1

According to the page lifecycle , the selectedvalue you are assigning in the Page_Load event overwrites the value you are setting in the button's OnClick event. You should try to match the page lifecycle when assigning values to your controls.

Answer 2

In Page_Load, do a check if it's a postback request. If it is, don't initialize your combo box.

if (!IsPostback) {
    cmbRequestState.SelectedValue = "2";
}