i was also facing the same issue so here is the solution
<input type="text" id="txtNumber1" name="txtNumber1" value="@Request["txtNumber1"]"/>
<input type="text" id="txtNumber2" name="txtNumber2" value="@Request["txtNumber2"]"/>
<input type="submit" id="btnSubmit" value="Add" />
<input type="text" id="txtNumber3" name="txtNumber3" value="@Request["txtNumber3"]"/>
actually when you post form the values get submitted to the server and a new form loads up
so this simple syntax allot the value property simply
value = "@Request["name of the text input"]"
and so on you can do for other text inputs