to solve this error "Unable to cast object of type 'NullStream' to type 'System.IConvertible'."

Question

 SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\cms.mdf;Integrated Security=True;User Instance=True");
        con.Open();
        SqlCommand cmd = new SqlCommand("selecthome", con);
        cmd.Parameters.Add("@monthlyachiever", SqlDbType.NVarChar).Value = monthlyachiever.Text;
        cmd.Parameters.Add("@topachiever", SqlDbType.NVarChar).Value = txttopachiever.Text;
        cmd.Parameters.Add("@training", SqlDbType.NVarChar).Value = txttraining.Text;
        cmd.Parameters.Add("@otherinformation", SqlDbType.NVarChar).Value = txtotherinformationhome.Text;
        cmd.Parameters.Add("@image", SqlDbType.Image).Value = Convert.ToByte( fileupload.FileContent);
        cmd.CommandText = "selecthome";
        string c1 = (string)cmd.Parameters["@monthlyachiever"].Value;
        Label6.Text = c1;
        string c2 = (string)cmd.Parameters["@topachiever"].Value;
        Label4.Text = c2;
        string c3 = (string)cmd.Parameters["@training"].Value;
        Label2.Text = c3;
        string c4 = (string)cmd.Parameters["@otherinformation"].Value;
        Label3.Text = c4;
        Image c5 = (Image)cmd.Parameters["@image"].Value;
        Image1 = c5;

    cmd.CommandType = CommandType.StoredProcedure;
    cmd.ExecuteNonQuery();
    con.Close();

Answer 1

The problem is this line: Convert.ToByte( fileupload.FileContent);

Since FileContent is a Stream you have to read the data from it, you cannot directly convert it to byte array.

See Creating a byte array from a stream on how to do that.