As i'm searching for solution to my problem there are no ways to make option within optgroup as a combobox.
Only design is what i got in w3schools.
<div class="form-group">
<label class="control-label" for="txt_ClientName">Option Group <span style="color: red;">*</span></label>
<select name="cars" id="cars" class="form-control">
<optgroup label="Swedish Cars">
<option value="volvo">Volvo</option>
<option value="saab">Saab</option>
</optgroup>
<optgroup label="German Cars">
<option value="mercedes">Mercedes</option>
<option value="audi">Audi</option>
</optgroup>
</select>
</div>
Are their any alternative to make it a combobox within optgroup that option should behave as a checkbox.