C# asp.net 中的列表框未获取所选项目
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Listbox in asp.net not getting selected items
提问by Learning
I have multiple dropdown & listbox in my webpage.
我的网页中有多个下拉列表和列表框。
I am trying to get a list of CategoryIDfrom a lstCatIDlistbox i am able to populate the listbox with category name.
我正在尝试CategoryID从lstCatID列表框中获取一个列表，我可以使用类别名称填充列表框。
If i remember correctly in first attempt my code worked fine, after that i made some change then it stated to always get the first item selected x No. of time
如果我在第一次尝试时没记错的话，我的代码运行良好，之后我做了一些更改，然后它声明始终选择第一个项目 x 时间
<asp:ListBox ID="lstCatID" runat="server" DataTextField="CategoryName"
DataValueField="CategoryID" SelectionMode="Multiple" CssClass="lstListBox">
</asp:ListBox>
protected void Button1_Click(object sender, EventArgs e)
{
string CatID = string.Empty;
foreach (ListItem li in lstCatID.Items)
{
if (li.Selected == true)
{
// Response.Write();
CatID += lstCatID.SelectedItem.Value + ",";
}
}
Response.Write(CatID);
}
I am not sure what is going wrong i checkd MSDN it show exactly the same way of doing it.
我不确定出了什么问题，我检查了 MSDN，它显示的方法完全相同。
May be i am doing something wrong.
可能是我做错了什么。
Just to add using firefox i am able to see multiple selected value have selected property.
只需使用 Firefox 添加，我就可以看到多个选定的值具有选定的属性。
<option value="3" selected="selected">One</option>
<option value="2">Two</option>
<option value="29" selected="selected">Three</option>
<option value="25" selected="selected">Four</option>
<option value="22" >Five</option>
My output in this case will be 3,3,3
在这种情况下我的输出将是 3,3,3
I would appreciate help in this regard
我将不胜感激这方面的帮助
采纳答案by MikeSmithDev
You are setting it to the same value every time:
您每次都将其设置为相同的值：
foreach (ListItem li in lstCatID.Items)
{
if (li.Selected == true)
{
// you are always using lstCatID.SelectedItem.Value.
CatID += lstCatID.SelectedItem.Value + ",";
}
}
When you actually want the value of the item in your loop that is selected:
当您真正想要循环中所选项目的值时：
foreach (ListItem li in lstCatID.Items)
{
if (li.Selected == true)
{
// get the value of the item in your loop
CatID += li.Value + ",";
}
}
回答by Rahul
Try to add Page.IsPostbackon your Page_Load like
尝试在您的 Page_Load 上添加Page.IsPostback
protected void Page_Load(object sender, EventArgs e)
{
// Do your API code here unless you want it to occur only the first
// time the page loads, in which case put it in the IF statement below.
if (!Page.IsPostBack)
{
}
}
Code:
代码：
protected void Button1_Click(object sender, EventArgs e)
{
string CatID = string.Empty;
foreach (ListItem li in lstCatID.Items)
{
if (li.Selected )
{
// TODO: Whatever you are doing with a selected item.
}
}
Response.Write(CatID);
}
Once i was facing the same problem and i made Postback mistake.
一旦我遇到同样的问题并且我犯了回发错误。
Hope it works.
希望它有效。
回答by Learning
I am not sure what is wrong with the logic i am using.
我不确定我使用的逻辑有什么问题。
I came across a nice solution using LINQ.
我使用 LINQ 遇到了一个很好的解决方案。
This single statement works great & gets me the desired results.
这个单一的语句效果很好，让我得到了想要的结果。
string values = String.Join(", ", lstCatID.Items.Cast<ListItem>().Where(i => i.Selected).Select(i => i.Value).ToArray());
RESULT: 3,29,25
结果：3,29,25
回答by waris kantroo
Get the selected items using linq
使用 linq 获取所选项目
var selected = lstCatID.Items.Where(i => i.Selected);
回答by user2596200
Minutes later I found a solution:
几分钟后，我找到了一个解决方案：
If lstLocations.Items.Count > 0 Then
For i As Integer = 0 To lstLocations.Items.Count - 1
If lstLocations.Items(i).Selected Then
'insert command
Dim selectedItem As String = lstLocations.Items(i).Text
End If
Next
End If
This worked fine in my scenario
这在我的场景中运行良好
