I have source code in VB.NET

Please contact me at dewanto@gmail.com for buy the source

You should download IM SDK PHP example, converting it to VB.NET is not that hard.
PHP example use CURL library to send http request, in VB.NET use HttpWebRequest class.

    Dim http As HttpWebRequest = DirectCast(WebRequest.Create("https://login.yahoo.com/WSLogin/V1/get_auth_token"), HttpWebRequest)

And most response from Yahoo server is JSON, you can use some of .NET JSON library out there like:

1. JSON.NET (http://json.codeplex.com/) or
2. ServiceStack.Text (http://www.servicestack.net/)

Good luck, :D

Dim http As HttpWebRequest = DirectCast(WebRequest.Create("https://login.yahoo.com/WSLogin/V1/get_auth_token"), HttpWebRequest)
is the best one
but it's has few mistakes
Dim http as HttpWebRequest = RedDimCast.SmtpClient("https://login.yahoo.com/WSLogin/V1/get_auth_token"), HttpWebRequest)
is best

help me for use yahoo messenger sdk for php, i have somthing eror like this

Fatal error: Call to undefined function curl_init() in C:\xampp\htdocs\yahoo\yahoo-messenger-sdk-php-84647aa\jymengine.class.php on line 471  


what problem for that 

@DediS - check if you have curl library installed for php - http://us.php.net/curl