Serialization problem when storing image in session while implementing sqlserver session state mode

I am implementing Session state to sql server mode in my web site and I am facing problem at this point

public void setCoverImage()
        {
            DateTime dt = new Da开发者_JAVA百科teTime();
            int dd = dt.Day;
            int mm = dt.Month;
            int yy = dt.Year;
            int hr = dt.Hour;
            int min = dt.Minute;
            int sec = dt.Second;
            int msec = dt.Millisecond;
            int tm = dd + mm + yy + hr + min + sec + msec;
            imgShowLogo.Src = "../../supportfiles/epub/cover.jpg?state=[" + tm + "]";
            //imgShowLogo.ImageUrl = "../../supportfiles/epub/cover.jpg?state=[" + tm + "]";
            Session["BookLogo"] = imgShowLogo;
        }

I am Facing problem here

"Unable to serialize the session state. In 'StateServer' and 'SQLServer' mode, ASP.NET will serialize the session state objects, and as a result non-serializable objects or MarshalByRef objects are not permitted. The same restriction applies if similar serialization is done by the custom session state store in 'Custom' mode. "

Please Help me ASAP and Thanks in advance.

Well, I think it would be enough to save only image url in session, not whole image.