Dynamically add DropDownCheckBoxes using C# in ASP.Net

Hi ganesh.gholap...,

Use below code.

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        var listBox = new Saplin.Controls.DropDownCheckBoxes
        {
            ID = "DropDownCheckBoxes1",
            UseSelectAllNode = false
        };

        ListItem item1 = new ListItem();
        item1.Text = "XYZ";
        item1.Value = "0";
        listBox.Items.Add(item1);

        ListItem item2 = new ListItem();
        item2.Text = "Testing XYZ";
        item2.Value = "1";
        listBox.Items.Add(item2);

        ListItem item3 = new ListItem();
        item3.Text = "Testing XYZ1";
        item3.Value = "2";
        listBox.Items.Add(item3);

        ListItem item4 = new ListItem();
        item4.Text = "Testing XYZ2";
        item4.Value = "3";
        listBox.Items.Add(item4);

        ListItem item5 = new ListItem();
        item5.Text = "Testing XYZ4";
        item5.Value = "4";
        listBox.Items.Add(item5);

        ListItem item6 = new ListItem();
        item6.Text = "Testing XYZ5";
        item6.Value = "5";
        listBox.Items.Add(item6);

        ListItem item7 = new ListItem();
        item7.Text = "Testing XYZ6";
        item7.Value = "6";
        listBox.Items.Add(item7);

        form1.Controls.Add(listBox);
    }
}

It will be rendered in the page as below when you do inspect. 

<div class="dd_chk_select" id="DropDownCheckBoxes1_sl" style="display: inline-block; position: relative;">
    <div id="caption">
        Select
    </div>
    <div class="dd_chk_drop" id="DropDownCheckBoxes1_dv" style="display: block; position: absolute;">
        <div id="checks">
            <span id="DropDownCheckBoxes1">
                <input name="DropDownCheckBoxes1$0" id="DropDownCheckBoxes1_0" type="checkbox" value="0"><label for="DropDownCheckBoxes1_0">XYZ</label><br>
                <input name="DropDownCheckBoxes1$1" id="DropDownCheckBoxes1_1" type="checkbox" value="1"><label for="DropDownCheckBoxes1_1">Testing XYZ</label><br>
                <input name="DropDownCheckBoxes1$2" id="DropDownCheckBoxes1_2" type="checkbox" value="2"><label for="DropDownCheckBoxes1_2">Testing XYZ1</label><br>
                <input name="DropDownCheckBoxes1$3" id="DropDownCheckBoxes1_3" type="checkbox" value="3"><label for="DropDownCheckBoxes1_3">Testing XYZ2</label><br>
                <input name="DropDownCheckBoxes1$4" id="DropDownCheckBoxes1_4" type="checkbox" value="4"><label for="DropDownCheckBoxes1_4">Testing XYZ4</label><br>
                <input name="DropDownCheckBoxes1$5" id="DropDownCheckBoxes1_5" type="checkbox" value="5"><label for="DropDownCheckBoxes1_5">Testing XYZ5</label><br>
                <input name="DropDownCheckBoxes1$6" id="DropDownCheckBoxes1_6" type="checkbox" value="6"><label for="DropDownCheckBoxes1_6">Testing XYZ6</label></span>
        </div>
    </div>
</div>