How can i upload files by using asp.net?

I assume you want to prompt the user to upload a file.

The server side form must include:

ENCTYPE="Multipart/Form-Data"

Now, we need to create the HtmlInputFile class instance,

<input type="file" id="ID"  runat="server" />

<![CDATA[<%-- The Web Form with the EncType property set to Multipart/Form-Data --%>
<form method="Post" enctype="Multipart/Form-Data"  runat="server">

   <%-- The File upload Html control --%>
   Choose Your File  To Upload <br>
   <input id="MyFile" type="File"  runat="server">
   <br>

   <%-- A button - when clicked the form is submitted and the
            Upload_Click event handler is fired... --%>
   <input type="Submit" value="Upload">
             OnServerClick="Upload_Click" RunAt="Server">

   ...
</input></br></input></br></form>