static dropdown select option

Question

here is my code , i want to get the selected index in c#. how to  get it in c# any hekp will be appreciated 

 

 

<select class="form-control" id="selectProduct" style="height: 35px">

<option id="optEmpty"></option>

<option id="optYES">YES</option>

<option id="optNO">NO</option>

</select>