C# 获取值以在回发下拉列表后保持选中状态

我的页面加载中有代码隐藏代码，它设置了一个下拉列表，列出文本和值。每当我选择一个值时，它都会重新加载页面，因为我已经打开了“自动发帖”。我需要该值即使在回发后仍保持选中状态。我该怎么做呢？下面是我的代码：

protected void Page_Load(object sender, EventArgs e)
{
    List<string> list = new List<string>
      { "Month", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12"};

    DropDownListMonth.DataSource = list;
    DropDownListMonth.DataBind();
    DropDownListMonth.SelectedIndex = 0;

    foreach (ListItem item in DropDownListMonth.Items)
    {
        int i = 0;
        string month = Convert.ToString(i);
        item.Value = month;
        i = Convert.ToInt32(month);
        i++;
    }   
}

---

有一个名为的页面属性，它指示页面是第一次呈现还是响应回发而加载

因此，您可以将此属性与if条件块一起使用，以避免ddl的重新绑定

protected void Page_Load(object sender, EventArgs e)
{
    if(!IsPostBack)
    {
      List<string> list = new List<string>
      { "Month", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12"};

    DropDownListMonth.DataSource = list;
    DropDownListMonth.DataBind();
    DropDownListMonth.SelectedIndex = 0;

    foreach (ListItem item in DropDownListMonth.Items)
    {
        int i = 0;
        string month = Convert.ToString(i);
        item.Value = month;
        i = Convert.ToInt32(month);
        i++;
    } 
  }  
}

您需要使用验证：

protected void Page_Load(object sender, EventArgs e)
{
    if(!Page.IsPostBack())
    {
        List<string> list = new List<string>
      { "Month", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12"};

        DropDownListMonth.DataSource = list;
        DropDownListMonth.DataBind();
        DropDownListMonth.SelectedIndex = 0;

        foreach (ListItem item in DropDownListMonth.Items)
        {
            int i = 0;
            string month = Convert.ToString(i);
            item.Value = month;
            i = Convert.ToInt32(month);
            i++;
        }
    }   
}

---

多亏了你和我读的另一页。谢谢你想知道为什么是负数：如果任何答案解决了你的问题，你应该点击旁边的复选标记接受它。

DropDownListMonth.DataSource = list;
DropDownListMonth.DataBind();
DropDownListMonth.SelectedIndex = 0;
string selectedValue=DropDownListMonth.SelectedItem.Tostring();
foreach (ListItem item in DropDownListMonth.Items)
{
       int i = 0;
       string month = Convert.ToString(i);
       item.Value = month;
       i = Convert.ToInt32(month);
       i++;
       if(item.Value.Tostring()==selectedValue)
       {
         item.Selected=true;
       }
}