Why can't I pass my Object into session created in Webservice

Question

Why can't I pass my Object into session created in Webservice?

[WebMethod]
public void UpdatedData(string CountryName, string CountryCode,
                        string City, string RegionCode, string RegionName) 
{            
    Chat ch = new Chat();
    ch.CountryName = CountryName;
    ch.CountryCode = CountryCode;
    ch.City = City;
    ch.RegionCode = RegionCode;
    ch.RegionName = RegionName;
    Session["Chat"] = ch;  //object Refrence not set to instance of an object
}

Answer 1

请在上面的方法上方放置以下代码：

[System.Web.Services.WebMethod(EnableSession=true)]

Answer 2

 [ WebMethod(Description="Per session Hit Counter",EnableSession=true)]
public void UpdatedData(string CountryName, string CountryCode, string City, string RegionCode, string RegionName) 
{
Chat ch = new Chat(); 
ch.CountryName = CountryName; 
ch.CountryCode = CountryCode; 
ch.City = City; ch.RegionCode = RegionCode; 
ch.RegionName = RegionName; 
Session["Chat"] = ch;
}