我有一个按钮，点击后会创建一个下拉列表。这部分代码正在运行。但是当再次单击相同的按钮时，我想删除新创建的下拉列表。删除下拉部分无效。总体目标是在用户需要时动态创建下拉列表，如果他想在创建后删除它，他应该可以。
<div style="border-style: dotted; font-family: 'Segoe UI'; border-width: 1px; height: 14%; position: relative;
width: 100%; top: 0px; left: 0px;">
<table style="width: 52%; position: relative; left: 90px; font-size: small; font-weight: 400;
top: 10px;">
<tr>
<td class="style1">
<span class="style5" style='color: red;'>*</span>Date:
</td>
<td>
<asp:TextBox ID="Date" runat="server" Style="position: relative; font-family: 'Segoe UI'; width: 100%" OnTextChanged="Date_TextChanged" AutoPostBack="True"></asp:TextBox>
<asp:CalendarExtender ID="Date_CalendarExtender" runat="server" TargetControlID="Date">
</asp:CalendarExtender>
</td>
<td colspan="2">
<asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server"
ErrorMessage="Enter Date" ControlToValidate="Date"
ValidationGroup="Submit_Validators"></asp:RequiredFieldValidator>
</td>
</tr>
<tr>
<td class="style1">
Day:</td>
<td>
<asp:TextBox ID="Day" runat="server" Style="position: relative; font-family: 'Segoe UI'; width: 100%"></asp:TextBox>
</td>
<td colspan="2">
</td>
</tr>
<tr>
<td class="style1">
Weather</td>
<td>
<asp:DropDownList ID="Weather" runat="server"
Style="position: relative; width: 100%" Font-Names="Segoe UI"
DataSourceID="WeatherOptions" DataTextField="Weather_Status"
DataValueField="Weather_Status">
</asp:DropDownList>
</td>
<td>
<asp:PlaceHolder ID="PlaceHolder1" runat="server">
</asp:PlaceHolder>
<asp:Button ID="Add_weather" runat="server" Text="+" OnClick="AddTextBox"
/>
</td>
<td>
</td>
</tr>
<tr>
<td class="style1">
Temperature</td>
<td>
<asp:TextBox ID="Temperature" runat="server"
Style="position: relative; font-family: 'Segoe UI'; width: 100%"></asp:TextBox>
</td>
<td colspan="2">
</td>
</tr>
<tr>
<td class="style1">
<span class="style5" style='color: red;'>*</span>Job #:
</td>
<td>
<asp:TextBox ID="JobNumber" runat="server" Style="position: relative; font-family: 'Segoe UI'; width: 100%"></asp:TextBox>
</td>
<td colspan="2">
<asp:RequiredFieldValidator ID="RequiredFieldValidator4" runat="server"
ErrorMessage="Enter Job Number" ControlToValidate="JobNumber"
ValidationGroup="Submit_Validators"></asp:RequiredFieldValidator>
</td>
</tr>
<tr>
<td class="style1">
Ticket #:</td>
<td>
<asp:TextBox ID="TicketNumber" runat="server"
Style="position: relative; font-family: 'Segoe UI'; width: 100%"
ReadOnly="True"></asp:TextBox>
</td>
<td colspan="2">
</td>
</tr>
<tr>
<td class="style1">
Customer Name:
</td>
<td>
<asp:TextBox ID="CustomerName" runat="server"
Style="position: relative; font-family: 'Segoe UI'; width: 100%"></asp:TextBox>
</td>
<td colspan="2">
</td>
</tr>
<tr>
<td class="style1">
Location/Project Name:
</td>
<td>
<asp:TextBox ID="Location" runat="server" Style="position: relative; font-family: 'Segoe UI'; width: 100%"></asp:TextBox>
</td>
<td colspan="2">
</td>
</tr>
<tr>
<td class="style1">
Project Manager:</td>
<td>
<asp:DropDownList ID="Manager" runat="server" DataSourceID="Product_Manager"
DataTextField="Name" DataValueField="Name"
Style="position: relative; width: 102%" Font-Names="Segoe UI">
<asp:ListItem></asp:ListItem>
</asp:DropDownList>
</td>
<td colspan="2">
</td>
</tr>
</table>
<br />
<table style="width: 52%; position: relative; left: 90px; font-size: small;">
<tr>
<td class="style47">
Start Time</td>
<td class="style47">
Finish Time</td>
<td class="style47">
Total Hours</td>
</tr>
<tr>
<td class="style42">
<asp:DropDownList ID="Start_Time" runat="server"
Style="position: relative; font-family: 'Segoe UI'; width: 100%"
AutoPostBack="True" onselectedindexchanged="Start_Time_SelectedIndexChanged">
</asp:DropDownList>
</td>
<td class="style42">
<asp:DropDownList ID="Finish_Time" runat="server"
Style="position: relative; font-family: 'Segoe UI'; width: 100%"
AutoPostBack="True" onselectedindexchanged="Finish_Time_SelectedIndexChanged">
</asp:DropDownList>
</td>
<td class="style42">
<asp:TextBox ID="Tkt_Total_Hours" runat="server"
Style="position: relative; font-family: 'Segoe UI'; width: 100%"
AutoPostBack="True" ontextchanged="Tkt_Total_Hours_TextChanged"></asp:TextBox>
</td>
</tr>
</table>
</div>
代码背后：
protected void AddTextBox(object sender, EventArgs e)
{
foreach (Control item in pnlPageRefresh2.Controls.OfType<DropDownList>())
{
if (item.ID == "weather2")
{
pnlPageRefresh2.Controls.Remove(item);
break;
}
}
create_cntrl();
}
protected void create_cntrl()
{
DropDownList weather2 = new DropDownList();
weather2.DataSourceID = "WeatherOptions";
weather2.DataTextField ="Weather_Status" ;
weather2.DataValueField = "Weather_Status";
pnlPageRefresh2.ContentTemplateContainer.Controls.Add(weather2);
PlaceHolder1.Controls.Add(weather2);
}
答案 0 :(得分：0)
请注意，在foreach循环中将其删除后，您只是再次创建下拉列表。
更新如下.. 如果找到了控件，则在未找到的情况下将其删除，然后按下面的方式创建它
protected void AddTextBox(object sender, EventArgs e)
{
bool found = false;
foreach (Control item in pnlPageRefresh2.Controls.OfType<DropDownList>())
{
if (item.ID == "weather2")
{
found = true;
pnlPageRefresh2.Controls.Remove(item);
break;
}
}
//check if not found then create it
if(!found)
{
create_cntrl();
}
}