Remove multiple items by value from dropdownlist C#

Question

I have one dropdownlist named drpdemo and consist some listitems as shown below

Design Code:

<asp:DropDownList ID="drpdemo" runat="server">
    <asp:ListItem Value="213">Select</asp:ListItem>
    <asp:ListItem Value="0">0</asp:ListItem>
    <asp:ListItem Value="2">2</asp:ListItem>
    <asp:ListItem Value="3">3</asp:ListItem>
    <asp:ListItem Value="4">4</asp:ListItem>
    <asp:ListItem Value="5">5</asp:ListItem>
    <asp:ListItem Value="0">0</asp:ListItem>
</asp:DropDownList>

Inline Code:

protected void Page_Load(object sender, EventArgs e)
{
    drpdemo.Items.Remove(drpdemo.Items.FindByValue("0"));
}

Current Output:

Select
  2
  3
  4
  5
  0

Above output comes with the 0, which i don't want it in output.

Expected Output:

Select
   2
   3
   4
   5

Note: Dont want to use any loop.

Please explain your aversion to loops. – canon Jan 09 '15 at 14:03 — canon, Jan 09 '15 at 14:03

score 5 · Accepted Answer · answered Jan 09 '15 at 13:52

You'll have to use a loop because Remove takes one ListItem and FindByValue returns only one ListItem.

To get the items to delete, we can do:

var toDelete = drpDemo.Items
               .Cast<ListItem>()
               .Where(i => i.Value == "0");

Then you can do:

foreach (var item in toDelete)
{
    drpDemo.Items.Remove(item);
}

Or if you're functionally inclined, do:

toDelete.ForEach(i => drpDemo.Items.Remove(i));

And all in one:

drpDemo.Items
    .Cast<ListItem>()
    .Where(i => i.Value == "0")
    .ToList()
    .ForEach(i => drpDemo.Items.Remove(i));

http://stackoverflow.com/questions/27936466/merge-2-or-more-rows-of-a-column-if-other-column-has-same-values-text-in-sqlserv — , Jan 14 '15 at 06:09

Christos · Answer 2 · 2015-01-09T14:30:30.840

1

If you look carefully to your drop down list, you will notice that there are two items with the same value, 0. So the method FindByValue finds the first and then you remove only this. If you had only one ListItem with value 0, then you wouldn't have seen it.

edited Jan 09 '15 at 14:30

answered Jan 09 '15 at 13:49

Christos

53,228
8
76
108

@Pranav you are correct I tested my code and I deleted it. Thanks :). – Christos Jan 09 '15 at 14:30

decPL · Answer 3 · 2015-01-09T14:27:22.743

1

Dropdown list does not support any method for removing multiple items at once so you will have to use a loop.

If you're ok with using a loop internally, but simply don't want to write one, you can always use LINQ (though I'll leave it for you to judge if it improves readability vs. using a loop).

drpdemo.Items
       .OfType<ListItem>()
       .Where(li => li.Value == "0")
       .ToList()
       .ForEach(li => drpdemo.Items.Remove(li));

edited Jan 09 '15 at 14:27

answered Jan 09 '15 at 13:53

decPL

5,384
1
26
36

@canon - I don't believe anything I wrote suggests doing so. If I missed anything, would you kindly point me to it? – decPL Jan 09 '15 at 14:08
Getting Error-does not contain a definition for 'Remove' and no extension method 'Remove' accepting a first argument of type 'System.Web.UI.WebControls.DropDownList' could be found (are you missing a using directive or an assembly reference?) – Jan 09 '15 at 14:10

Remove multiple items by value from dropdownlist C#

3 Answers3

Linked