Merge two images to create a single image in C#.Net

private void Merge _Click(object sender, EventArgs e)
{
}
DirectoryInfo directory=new DirectoryInfo("D:\\Images");
if(directory!=null)
{
    FileInfo[]files = directory.GetFiles();
    MergeImages(Image);
}

private void MergeImages(FileInfo[] Image)
{
    //change the location to store the final image.
    string FImage= @"D:\\Images\\FImage.jpg";
    List imageHeights = new List();
    int nIndex = 0;
    int width = 0;
    foreach (FileInfo file in files)
    {
        Image img = Image.FromFile(file.FullName);
        imageHeights.Add(img.Height);
        width += img.Width;
        img.Dispose();
    }
    imageHeights.Sort();
    int height = imageHeights[imageHeights.Count - 1];
    Bitmap NewImg = new Bitmap(width, height);
    Graphics Gr= Graphics.FromImage(NewImg);
    Gr.Clear(SystemColors.AppWorkspace);
    foreach (FileInfo file in files)
    {
        Image img = Image.FromFile(file.FullName);
        if (nIndex == 0)
        {
            Gr.DrawImage(img, new Point(0, 0));
            nIndex++;
            width = img.Width;
        }
        else
        {
            Gr.DrawImage(img, new Point(width, 0));
            width += img.Width;
        }
            img.Dispose();
    }
    Gr.Dispose();
    NewImg .Save(FImage, System.Drawing.Imaging.ImageFormat.Jpeg);
    NewImg .Dispose();
    imageLocation.Image = Image.FromFile(FImage);
}

I have api for that at http://bookingbillboard.com/API. This api will combine 2 pictures. 1 picture is your images/design/poster, and other images is photo of billboard. by using API , you can see how your design/images/poster looks like in the photo of billboard