VC.Net How to use BitmapData to make a UserControl (OnPaint)?

I write a UserControl. The UserControl can show Speed. So I must use Bitmap.LockBits and then get Bitmap Start Address( BitmapData.Scan0 ). The code put UserControl OnPaint Event.

The code like following.

namespace CTest

{

  public partial class uc_Thermometer_08 : UserControl
  {

      //protected override void OnPaint(PaintEventArgs e)

      {

           .........

           unsafe
            {
             ...........
                bmpdat_Tmp = bmp_Tmp.LockBits(new Rectangle(0, 0, bmp_Tmp.Width-1,bmp_Tmp.Height-1),ImageLockMode.ReadWrite,PixelFormat.Format24bppRgb);
    
    
    byte_Ptr = (byte*)bmpdat_Tmp.Scan0;

        int_Stride = bmpdat_Tmp.Stride;
        ........fill Color           
                    
        bmp_Tmp.UnlockBits(bmpdat_Tmp);
    }

   }

 }

I open other new project and put my UserControl on the form. It's ok. But I Close all project. And then I open again in vs2010. But the UserControl show error message as following situation.

But if I select the code edit page and close all project. I reopen all projects then select form design page. It show OK. Please give me a idea. Thanx.