asp.net - 更改嵌套转发器内下拉列表的选定值

Question

我尝试从 C# 代码更改下拉列表选定的值:

<repeater >
   <repeater> 
      <dropdown>

我将 aspx 页面中的数据源添加到下拉列表中一切正常..但我想更改下拉列表中选定的值编辑表格时能够向用户显示之前选择的名称

protected void PrepairDropDownList(object sender,EventArgs e)
    {
        shiftrepeater.DataBind();
        if (shiftrepeater.Items.Count > 0)
        {
            for (int shiftcount = 0; shiftcount < shiftrepeater.Items.Count; shiftcount++)
            {
                Repeater temp = (Repeater)shiftrepeater.Items[shiftcount].FindControl("saturdayrepeater");
                if (temp.Items.Count > 0)
                {
                    for (int count = 0; count < temp.Items.Count; count++)
                    {
                        DropDownList ds = (DropDownList)temp.Items[count].FindControl("userdropdown");
                        HiddenField hf = (HiddenField)temp.Items[count].FindControl("hiddenid");//contain the id if the field 
                        SarcShiftUser user = CRUD<SarcShiftUser>.Get(int.Parse(hf.Value)); //a method to select a user with a specific id and add it to object from class sarcshiftuser

                        if (user.id == 0)
                            ds.SelectedValue = "";
                        else
                        {
                            ds.SelectedValue = user.user_id + "";

                        }
                    }
                }

            }
        }
        shiftrepeater.DataBind();
    }

我将此方法添加到中继器的 Onload 中:但没有任何变化，以前的名字也没有显示

P.S:用户对象是正确的，user.user_id也是正确的P.S 2:我尝试添加 ds.DataBind();更改所选内容后但出现错误:

System.ArgumentOutOfRangeException: 'userdropdown' has a SelectedValue which is invalid because it does not exist in the list of items.

Answer 1

设置 DropdownList 的 SelectedItem 的最安全方法是设置 SelectedIndex，如下所示:

ds.SelectedIndex = ds.Items.IndexOf(ds.Items.FindByValue(user.user_id.ToString()));