的EnableViewState不DropDownList的工作 [英] EnableViewState not working in DropDownList

问题描述

Default.aspx页面有一个的DropDownList 这是在人口仅次于code，当它不是一个回发。当选择一个值的方法被称为填补一个文字与所选值。它按预期工作。问题是，当我不的EnableViewState 使其在的DropDownList 控制只设置页面。在这种情况下，当回发的的DropDownList 失去了它的项目。我已经安装一个新的Web项目只是为了测试这一点。有没有高手页面，使其更简单。

The default.aspx page has a DropDownList which is populated in the code behind only when it is not a postback. When a value is selected a method is called which fills a Literal with the selected value. It works as expected. The problem is when I set the page to not EnableViewState enabling it in the DropDownList control only. In this case when posted back the DropDownList loses its items. I have setup a new Web project just to test this. There is no master page to make it simpler.

Default.aspx的：

Default.aspx:

<%@ Page Title="Home Page" Language="C#" AutoEventWireup="true"
    CodeBehind="Default.aspx.cs" Inherits="WebApplication4._Default" 
    EnableViewState="false" %>

<asp:DropDownList ID="DDL" runat="server" 
    OnSelectedIndexChanged="DDL_OSIC" 
    AutoPostBack="true" 
    EnableViewState="true">
</asp:DropDownList>

<asp:Literal ID="Literal1" runat="server"></asp:Literal>

Default.aspx.cs：

Default.aspx.cs:

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        DDL.Items.Add("red");
        DDL.Items.Add("green");
        DDL.Items.Add("blue");
    }
}
protected void DDL_OSIC(object sender, EventArgs e)
{
    Literal1.Text = DDL.SelectedValue;
}

为什么不工作的EnableViewState？

Why isn't EnableViewState working?

推荐答案

找到了已删除的答案的帮助答案。被删除的答案是错的，只是因为它是不完整的。与暗示我发现的ViewStateMode属性页

Found the answer with the help of a deleted answer. The deleted answer was wrong just because it was incomplete. With that hint I found the ViewStateMode Property page.

总结它禁用所有控件的ViewState中并启用它只是用于已选定的：

Summarizing it to disable all controls' ViewState and enable it just for the choosen ones:

• 设置两个页面，所有控件的的EnableViewState 属性真正。这是默认的，因此没有必要写什么


• 设置页面 ViewStateMode 到禁用


• 设置 ViewStateMode 到在你想要启用ViewState的控制已启用

• Set both the page and all the control's EnableViewState property to true. This is the default so it is not necessary to write anything
• Set the page ViewStateMode to Disabled
• Set ViewStateMode to Enabled in the control where you want ViewState enabled

这篇关于的EnableViewState不DropDownList的工作的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！