Windows mobile application background problem

Answer 1

First of all, your code needs some clean up:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Reflection;
using Microsoft.WindowsMobile.Status;

namespace My_Mobile
{
    public partial class MainForm : Form
    {

        Globals _globals = new Globals();

        Bitmap backgroundVertical = null;
        public MainForm()
        {
            InitializeComponent();
            backgroundVertical = new Bitmap(_globals.ApplicationPath + @"\Resources\wallpaper.bmp");
        }

        private void MainForm_Load(object sender, EventArgs e)
        {
        }


        protected override void OnPaintBackground(PaintEventArgs e)
        {
            //base.OnPaintBackground(e);
        }


        protected override void OnPaint(PaintEventArgs e)
        {
             using (Bitmap buffer = new Bitmap(this.Width, this.Height))
             using (Graphics gfx = Graphics.FromImage(buffer))
             {
                gfx.Clear(this.BackColor);
                gfx.DrawImage(backgroundVertical, 0, 0);
                //this.Invalidate();  Don't call Invalidate here, it shouldn't be needed
                e.Graphics.DrawImage(buffer, 0, 0);
             }
        }
    }
}

Chris Tacke's classic blog talks about Bitmaps in the CF. You need to be careful:

http://blog.opennetcf.com/ctacke/PermaLink,guid,987041fc-2e13-4bab-930a-f79021225b74.aspx

After all that, I'm not really sure what your question is. Could you be more specific? Like for example, I don't see any P/Invokes, but you said you used some. Where are they?