错误：异常详细信息：System.ArgumentOutOfRangeException：'dropdownlist1'具有SelectedValue，该ListValue无效，因为它在项列表中不存在。参数名称：value [英] Error: Exception Details: System.ArgumentOutOfRangeException: 'dropdownlist1' has a SelectedValue which is invalid because it does not exist in the list of items. Parameter name: value

问题描述

当数据库是空的从分贝检索数据时进入下拉列表给出了这样的eror



异常详细信息：System.ArgumentOutOfRangeException： '' dropdownlist1 '' 具有的SelectedValue这是无效的，因为它不存在于项目列表中。

参数名称：值



i尝试了这个：

when the database is empty gives this eror when retrieving data from db into dropdownlist.

Exception Details: System.ArgumentOutOfRangeException: ''dropdownlist1'' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value

i have tried this one:

if (dt.Rows[rowIndex]["Zone"].ToString() == null || dt.Rows[rowIndex]["Zone"].ToString() == "")

                           dropdownlist1.SelectedValue = null;
                       else
                          dropdownlist1.SelectedValue = dt.Rows[rowIndex]["Zone"].ToString();

但是问题是它在这种情况下需要数据的第一个值，我已经绑定了下拉列表...

如果没有数据，我怎么能省空？

BUT the problem is that it takes in this case the first value of the datable, i have bind the dropdownlist...
HOW CAN I LEAVE IT EMPTY WHEN THERE IS NO DATA??

推荐答案

只需将一个空项添加到下拉列表中就可以解决这个问题了，然后选择它？



类似于：

Would it be a solution for you to just add an empty item to the dropdownlist, and then select it?

something like:

dropdownlist1.Items.Insert(0, "");
dropdownlist1.SelectedIndex(0);

您只需要设置选项如果下拉列表中有任何记录。尝试：

You need to set the option only if there is any record in dropdown. Try:

if (dt.Rows.Count > 0)
{
  // Your logic regarding data - setting control values , etc
  ...
  ...
  dropdownlist1.SelectedValue = dt.Rows[rowIndex]["Zone"].ToString();
  ...
  ...
}

这篇关于错误：异常详细信息：System.ArgumentOutOfRangeException：'dropdownlist1'具有SelectedValue，该ListValue无效，因为它在项列表中不存在。参数名称：value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！