Session got kill after posting data to another application & getting back through post even from same destination in ASP.NET ?

Using HttpPost method as per below code:-

public string PreparePOSTForm(System.Web.UI.Page myPage, string formID, string url, System.Collections.Hashtable data) // post form
{
//Set a name for the form
//string formID = "PostForm";
//Build the form using the specified data to be posted.
StringBuilder strForm = new StringBuilder();
strForm.Append("");

foreach (System.Collections.DictionaryEntry key in data)
{
strForm.Append("");
}

strForm.Append("");
//Build the JavaScript which will do the Posting operation.
StringBuilder strScript = new StringBuilder();
strScript.Append("");
strScript.Append("var v" + formID + " = document." +
formID + ";");
strScript.Append("v" + formID + ".submit();");
strScript.Append("");
//Return the form and the script concatenated.
//(The order is important, Form then JavaScript)

myPage.Controls.Add(new LiteralControl(strForm.ToString() + strScript.ToString()));

return strForm.ToString() + strScript.ToString();
}