C#

 Bitmap currentStitch = null;
       private void StitchImage(object sender)
       {
           for (int i = 0; i < FrameList.Count; i++)
           {
               if (currentStitch == null) currentStitch = (Bitmap)FrameList[i].Clone();
               else
                   AddCurretnSlice(FrameList[i]);
           }
       }

private void AddCurretnSlice(Bitmap Slice)
       {
           Bitmap newStitch = new Bitmap(currentStitch.Width + Slice.Width, Slice.Height);
           BitmapData destinationData = newStitch.LockBits(new Rectangle(0, 0, newStitch.Width, newStitch.Height), ImageLockMode.ReadWrite, currentStitch.PixelFormat);
           BitmapData overlayData = currentStitch.LockBits(new Rectangle(0, 0, currentStitch.Width, currentStitch.Height), ImageLockMode.ReadOnly, currentStitch.PixelFormat);
           BitmapData sourceData = Slice.LockBits(new Rectangle(0, 0, Slice.Width, Slice.Height), ImageLockMode.ReadOnly, Slice.PixelFormat);
           try
           {
               int dstHeight = destinationData.Height;
               int src1Height = overlayData.Height;
               int src2Height = sourceData.Height;

               int src1Stride = overlayData.Stride;
               int src2Stride = sourceData.Stride;
               int dstStride = destinationData.Stride;

               int pixelSize = System.Drawing.Image.GetPixelFormatSize(sourceData.PixelFormat) / 8;
               int copySize1 = overlayData.Width * pixelSize;
               int copySize2 = sourceData.Width * pixelSize;

               // do the job
               unsafe
               {
                   byte* src1 = (byte*)overlayData.Scan0.ToPointer();
                   byte* src2 = (byte*)sourceData.Scan0.ToPointer();
                   byte* dst = (byte*)destinationData.Scan0.ToPointer();

                   // for each line
                   for (int y = 0; y < dstHeight; y++)
                   {
                       if (y < src1Height)
                           AVision.SystemTools.CopyUnmanagedMemory(dst, src1, copySize1);
                       if (y < src2Height)
                           AVision.SystemTools.CopyUnmanagedMemory(dst + copySize1, src2, copySize2);

                       src1 += src1Stride;
                       src2 += src2Stride;
                       dst += dstStride;
                   }
               }

           }
           finally
           {
               newStitch.UnlockBits(destinationData);
               currentStitch.UnlockBits(overlayData);
               Slice.UnlockBits(sourceData);

               currentStitch.Dispose();
               currentStitch = newStitch;
           }
       }

Thread allows the highest degree of control; you can Abort() or Suspend() or Resume() a thread (though this is a very bad idea)

// Windows Form

namespace skbtInstaller
{
    public partial class frmMainWindow : Form
    {
        public frmMainWindow()
        {
            InitializeComponent();
	
	    // coxArmaPath = Combo Box (simple drop down)
            this.cBoxArmaPath.ValueMember = "Key";
            this.cBoxArmaPath.DisplayMember = "Value";
	    // ....
        }

        public void addServerPathItem(String Key, String Value)
	{
            this.cBoxArmaPath.Items.Add(new KeyValuePair<String, String>(Key,Value));
	    // This works fine, only the "DisplayMember" is displayed and the "ValueMember" is hidden.
        }

	// This acts differently with the same types???
        public void setServerPathDatasource(List<KeyValuePair<String, String>> source)
        {
            this.cBoxArmaPath.DataSource = new BindingSource(source, null);
        }
    }

    public class skbtServerControl
    {
        private frmMainWindow frmMainWindowHandle;
        public void refreshformWindow()
        {
            // Clear Drop Box (empties drop box)
            this.frmMainWindowHandle.clearPathBox();

	    //skbtServerConfig is very simple property object
            foreach (KeyValuePair<String, skbtServerConfig> pair in CoreConfig.getServerConfigList())
            {
                // Populate Drop Box
                this.frmMainWindowHandle.addServerPathItem(pair.Key, pair.Value.getTextualName()); // this works as intended
                // cBox gets items like: Some Display Text, Some Display Text, Some Display Text (PERFECT!)
            }
        }
	
	// This works absolutely fine. ValueMembers are hidden.
        public void refreshformWindowWithSTATICDatasource()
        {
            // Clear Drop Box
            this.frmMainWindowHandle.clearPathBox();

            var pathDataSource = new List<KeyValuePair<String, String>>() 
            {
                new KeyValuePair<String, String>("testKey1", "somevalue1"),
                new KeyValuePair<String, String>("testKey2", "somevalue2"),
                new KeyValuePair<String, String>("testKey3", "somevalue3")
            };

            // Populate Drop Box
            this.frmMainWindowHandle.setServerPathDatasource(pathDataSource);
	    // cBox gets items like: Some Display Text, Some Display Text, Some Display Text (PERFECT!)
        }
	
	// ** HERE IS THE PROBLEM?? **
	// This creates a type that seems different to the above function which works fine...
        public void refreshformWindowWithDatasource()
        {
            // Clear Drop Box
            this.frmMainWindowHandle.clearPathBox();

            var pathDataSource = new List<KeyValuePair<String, String>>();

            //skbtServerConfig is very simple property object
            foreach (KeyValuePair<String, skbtServerConfig> pair in CoreConfig.getServerConfigList())
            {
                pathDataSource.Add(new KeyValuePair<String, String>(pair.Key, pair.Value.getTextualName()));
            }

            // Populate Drop Box
            this.frmMainWindowHandle.setServerPathDatasource(pathDataSource);
	    // cBox gets items like [asjAETJQ5785d45,Some Display Text], [asawfgQ5785d45,Some Display Text], [asjAhrrQ5785d45,Some Display Text]
	    // ????? surely this function should act exactly like the function above??
        }
    }
}