清除后更新下拉列表的值 [英] updating value of drop down list after clear them

问题描述

我有2个具有sql值的下拉列表，这些sql列表也具有初始值，因此从第一个下拉列表中选择后第二个下拉列表也会更改，因此我应该在第一笔更改发生后清除第二个下拉列表的值，但先清除第一个下拉列表后列出我的初始值没有出现，我应该如何在清除代码后显示我的初始值?

第一个下拉列表:

I have 2 dropdown list with sql value that have initial value too that second drop down list changes after selecting from first drop down list so I should clear second drop down list value after changes happen in fist one but after clearing first drop down list my intial value doesn''t appear what should I do in my behind code to show my initial value after clearing?

first dropdown:

<asp:dropdown ID="OrderNo" runat="server"   MaxLength="0" style="display: inline;"  AppendDataBoundItems="True" DataSourceID="OrderNo_SqlDS" DataTextField="OrderNo"  DataValueField="OrderNo" onselectedindexchanged=" OrderNo_SelectedIndexChanged" AutoPostBack="true"> <asp:ListItem Text="--Select One--" Value="" /></asp:dropdown> 

第二个下拉菜单:

Second dropdown:

<asp:dropdown ID="Part" runat="server"   MaxLength="0" style="display: inline;"  AppendDataBoundItems="True" DataSourceID="Part_SqlDS" DataTextField="Part"  DataValueField="Part" onselectedindexchanged=" Part_SelectedIndexChanged" AutoPostBack="true"> <asp:ListItem Text="--Select One--" Value="" /></asp:dropdown>

并在我的背后代码中:

and in my behind code:

protected void OrderNo_SelectedIndexChanged(object sender, EventArgs e)     
{ 
Part.Items.Clear(); 
Part.DataBind();  
   }

推荐答案

亲爱的朋友，

从您的问题中我了解到的是，如果是这种情况，则要检索第一个下拉列表的初始值，则只需在更改或清除之前(在您的情况下)将初始值保存在隐藏字段中，然后然后将数据绑定到第一个下拉列表之后再次选择相同的字段，如:-

Dear Friend,

What I understood from your question is that you want to retrieve the initial value of the first drop-down if this is the case then you just have to save the initial value in the hidden field before changing or clearing it (in your case) and then select the same field again after binding data to the first drop down like :-

//Before changing or clearing the drop down data
HiddenField hdnID= ddlFirst.SelectedValue;
//After binding data again
ddlFirst.SelectedValue=hdnID.Value;

希望这能解决您的问题.

谢谢

I hope this will solve your problem.

Thanks

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