asp.net web form to Db

I have very long old asp.net web form with alot of fields, and I hope to save the data. However, since there is so many fields over 500+, doing it manually will take so much time.

I hope I can use the id e.g. field1 as xml child and the value, and loop all of the fields inside of <form runat=server></form>

e.g.
<xml>
<trans>
<field1>field1_value</field>
</trans>
</xml>

Then, I take the xml string and save it into table1. I know how to save the xml string into table1.
But I do not know how to code that xml, and loop inside of the <form></form> in code behind c#