Parameterized Query expects parameter which was not supplied.

Hello .....

I am developing a project where I am to retrieve image from database to display in GridView control. My image was stored on database in Binary Format not as a link. I am also using Handler.ashx file for to process my request and return a response to the browser. But unfortunately I am getting this error:

Parameterized Query '(@ImageId int)Select Image_Content, Image_Type from ImageGallery' expects parameter @ImageId, which was not supplied. Statement(s) could not be prepared.


My Handler.ashx Page Code

public void ProcessRequest (HttpContext context)
    {
          //context.Response.ContentType = "text/plain";
          //context.Response.Write("Hello World");
          SqlConnection myConnection = new SqlConnection(ConfigurationManager.ConnectionStrings["DatabaseConnectionString1"].ConnectionString);
          myConnection.Open();
          string sql = "Select Image_Content, Image_Type from ImageGallery where Img_Id=@ImageId";
          SqlCommand cmd = new SqlCommand(sql, myConnection);
          cmd.Parameters.Add("@ImageId", SqlDbType.Int).Value = context.Request.QueryString["id"];
          cmd.Prepare();
          SqlDataReader dr = cmd.ExecuteReader();   // there is my error
          dr.Read();
          context.Response.ContentType = dr["Image_Type"].ToString();
          context.Response.BinaryWrite((byte[])dr["Image_Content"]);
          dr.Close();
          myConnection.Close();
    }


My Default.aspx Page Code

                    EmptyDataText="There are no data records to display." Width="540px">
           
               
               
               
                   
                   
                   
               
           
           
       
                    ProviderName="<%$ ConnectionStrings:DatabaseConnectionString1.ProviderName %>"
            SelectCommand="SELECT [Img_Id], [Image_Content], [Image_Type], [Image_Size] FROM [ImageGallery]">
       




In Handler.ashx page I am getting error, I have underlined above in code.


Please fix it.........