ASP.NET

__doPostBack('RAISE_Your_Event','specify_argument_here_if_needed');

if (this.IsPostBack)
{
    // Insure that the __doPostBack() JavaScript method is created...
    this.GetPostBackEventReference(this, string.Empty);

    string eventTarget = (this.Request["__EVENTTARGET"] == null) ? string.Empty : this.Request["__EVENTTARGET"];


    if (eventTarget == "RAISE_Your_Event")
    {
        string argumentValue  =  (this.Request["__EVENTARGUMENT"] == null) ? string.Empty : this.Request["__EVENTARGUMENT"];
    }
}

string query = "SELECT Image FROM TAB_Employee WHERE EmpID='" + EmpID + "'";
SqlCommand cmdImg = new SqlCommand(query, gCnn);
byte[] image = (byte[])cmdImg.ExecuteScalar();
MemoryStream mstream = new MemoryStream(image);
Bitmap bitmap = new Bitmap(System.Drawing.Image.FromStream(mstream));
Response.ContentType = "image/gif";
bitmap.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Gif);
bitmap.Dispose();