How to limit ASP.NET ListBox selection while its selection mode is multiple.

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Hello All,

I am binding ListBox in code behind page using data from database. I have set its selection mode to be multiple. However I have to inhibit Listbox from getting selected more that 3 values.

I spent a lots of time on google but no use, Please help me out.

Thanks,

Posted 17-Sep-14 11:07am

NAPorwal(8015059)

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Sergey Alexandrovich Kryukov 17-Sep-14 18:38pm

Why doing so?
—SA

NAPorwal(8015059) 17-Sep-14 18:46pm

On the basis of user attributes, I have to restrict them while selecting items from the ListBox. That's why need to do so.

Sergey Alexandrovich Kryukov 17-Sep-14 19:16pm

This is like saying: "I need to restrict number of selected items in ListBox, because I have to restrict them while selecting items from the ListBox". if you don't want to answer, don't. I suggested you a reasonable solution, please see.
—SA

NAPorwal(8015059) 17-Sep-14 19:31pm

Yes, I am going through those only, I hope it's going to work.

2 solutions

Solution 1

Well, if I look at Google with the search term asp.net listbox multiple selection maximum[^], the first few post themselves are promising and directive enough. Please have a look and show us what you have tried.

If you are still stuck, come back and someone will try to help you with your issue.

Posted 17-Sep-14 11:10am

Manas Bhardwaj

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Sergey Alexandrovich Kryukov 17-Sep-14 18:38pm

Manas,

This information could be useful, but, unfortunately, this is not a solution to the OP's problem. Showing Google queries cannot be adequate in all cases, otherwise this forum would not be needed.
I am sure that real solution is the different UI design. I suggested much more reasonable design and motivated it (as well as the problems of OP's idea) in Solution 2, please see.

—SA

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Sergey Alexandrovich Kryukov · Accepted Answer · 2014-09-17T12:36:00

I would strongly advise you to review your UI design instead. This control is really designed to represent arbitrary selection from 0 to N items, where N is the total number of items. When you try to break this design, the component will strongly resist. Worse, if you succeed, it will be way too confusing to the users who usually expect default and reasonable behavior.

I think at least one more reasonable design is nearly obvious. Instead of having a list box, have a set of combo boxes. Even better, it would be ideal to use an instance of the class System.Web.UI.WebControls.TreeView with combo-boxes on nodes. All you would need is to set the property ShowCheckBoxes and use the property CheckedNodes:

Please see:
http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.treeview%28v=vs.110%29.aspx[^],
http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.treeview.showcheckboxes%28v=vs.110%29.aspx[^],
http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.treeview.checkednodes%28v=vs.110%29.aspx[^].

Now, you want to limit the number of checks. You will need to handle the event TreeNodeCheckChanged. Create some other control and display the checking status, for example "0 of 3 values checked", "1 of 3 values checked"… "3 of 3 values checked". It will provide the user with some feedback, it will become apparent that limited number of checks would be allowed. Always allow unchecking, but block checking more nodes above your limit.

—SA