How to Use CheckBox Selection Limit in ASP.NET

In this article I will teach you how to limit the number of selected items among all the checkboxes on a webpage. The first step is to create an "ASP.NET Empty Web Application".

Since we have started with an Empty Web Application we need to add a page now. Go to Project > Add New Item (Ctrl+Shift+A); a screen will pop up; add a web form from it and name it "SelectionLimit.aspx".

The explorer will have SelectionLimit.aspx open for you with some default code. Add a Check Box List either from a toolbox or write the code. Since we need to limit the number of selections we need to call a function or submit our form every time a selection is made in the check box list. For this we will use the property AutoPostBack; set it to "true" since we need to call a function on every Post Back to trigger an event when the selection changes. To do this go to the properties on the bottom-right corner.





As soon as you double-click the SelectedIndexChanged, "SelectionLimit.aspx.cs" will show up where you will write code.

We will have the following two functions there:

protected void Page_Load(object sender, EventArgs e), and
protected void MyCheckBoxList_SelectedIndexChanged(object sender, EventArgs e)

Since we have just added CheckBoxList and not added any items to it, so in the "Page_Load" Function we will add items to the CheckBoxList:



And in the "MyCheckBoxList_SelectedIndexChanged" function we will do the main coding part:

That is all. Debug your page, you might have noticed in the "if" condition that I used count > 2 i.e. I'm limiting the selection to two selections only i.e. only two items can be selected.