CheckBoxList

Checkboxlist is used to provide a list of checkboxes that can be created dynamically by binding it to the data source.Checkbox is used to select a single value while checkboxlist is used to get a group of information from the user.
How t Bind a Checkboxlist to Datasource:

To bind a checkboxlist to datasource first add the checkboxlist control into your page.When the checkboxlist control is added to your page then a smart tag appears which allows you to specify a datasource or add a items manually to the checkboxlist.Also click on Edit Items to open the ListItem collection editor and add items as shown infigure below:

How to Add items Programmatically in CheckBoxLIst:
If you want to add items to checkboxlist programmatically, use the following code.

protected void Page_Load(object sender, EventArgs e)

    {

        if (!Page.IsPostBack)

        {

            cblMulti.Items.Add(new ListItem("Items 1", "Items 1"));

            cblMulti.Items.Add(new ListItem("Items 2", "Items 2"));

            cblMulti.Items.Add(new ListItem("Items 3", "Items 3"));

        }

    }

Here in the code cblmulti.Items.Add take the augument of New ListItem whereas ListItem takes two argument first is Text and Second is Value.