How to clear all fields like DropDownList TextBox after Form submission in ASP.Net

hi , i am using html input fields for inserting data to db e.g.:

   <input type="text" runat="server" ClientIDMode="Static" id="StreetNo" class="form-control input-mask-phone"/>

and a submit button for submitting all data :

<button class="btn btn-info btn-block"  style="height: 40px;" OnServerClick="SubmitProject_OnServerClick" ValidationGroup="Date" type="button" runat="server" ClientIDMode="Static" id="SubmitProject"> Submit   </button>

also i am using an update panel to trigger this button click event ( to avoid postbacks and page refreshing ) . i want to clear out all my fields after submition of data , but it won't happens , even i tried on submit_click's event also , i did :

/// after submittion

StreetNo.Value = string.Empty;

but nothing happend ..