how to create parameters for http post request.

Hi
I am new to asp.net form. so please forget if any thing is wrong
I am creating a web application which will generate http web request with "post" method and pass multiple parameter which I am concatenating using stringbuilder see below
StringBuilder postData = new StringBuilder(); postData.Append("accountNo=" + HttpUtility.UrlEncode("123") + "&"); postData.Append("accountName=" + HttpUtility.UrlEncode("ABC") );
I want to send different parameter base on different condition.
For example one senerio can be
1) send only account no
2) send only account Name
3) send both in parameter.
Would like to know how to create parameters for http post request.
 
 
any advice (new to web request )
 
Regards
 
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