ASP:ListBox Get Selected Items - One Liner?

问题

I am trying to get the selected items of an asp:ListBox control and put them in a comma delimited string. There has got to be a simpler way of doing this then:

foreach (ListItem listItem in lbAppGroup.Items)
{
    if (listItem.Selected == true)
    {
        Trace.Warn("Selected Item", listItem.Value);
    }
}

Is there a way to get this into one line? like my pseudo code here:

string values = myListBox.SelectedItems;

I am using ASP.NET and C# 3.5.

Thanks for any help!!

回答1:

Using LINQ:

string values = String.Join(", ", lbAppGroup.Items.Cast<ListItem>()
                                                  .Where(i => i.Selected)
                                                  .Select(i => i.Value));

回答2:

I don't think there is anything built in but you could do something like this:

  <asp:ListBox runat="server" ID="listBox" SelectionMode="Multiple">
    <asp:ListItem Selected="True" Text="text1" Value="value1"></asp:ListItem>
    <asp:ListItem Selected="false" Text="text2" Value="value2"></asp:ListItem>
    <asp:ListItem Selected="True" Text="text3" Value="value3"></asp:ListItem>
    <asp:ListItem Selected="True" Text="text4" Value="value4"></asp:ListItem>
</asp:ListBox>

    IEnumerable<string> selectedValues = from item in listBox.Items.Cast<ListItem>()
                                             where item.Selected
                                             select item.Text;

        string s = string.Join(",", selectedValues);

回答3:

var selectedQuery = listBox.Items.Cast<ListItem>().Where(item => item.Selected); 
string selectedItems =  String.Join(",", selectedQuery).TrimEnd();

回答4:

Actually there IS something built in:

ListBox.getSelectedItems

http://msdn.microsoft.com/en-us/library/aa297606(v=vs.60).aspx

回答5:

Another way is to use the Request Form object which contains everything that was posted back. eg:

string values = Request.Form(lbAppGroup.UniqueID);  //returns "a,b" if they were selected

This by default returns a comma delimited list of selected items. I sometimes use this way when I don't want or need to bind the data again but still want to get the selected values for processing.

来源：https://stackoverflow.com/questions/8478992/asplistbox-get-selected-items-one-liner