Question

Baiscally, I’m trying to draw an image, with a big number (my iteration variable’s current value) on it:

var imageList = new List<Image>();

for (int i = 1; i <= totalCount; i++)    
{
    using (Bitmap bmp = new Bitmap(800,2000))
    using (Graphics g = Graphics.FromImage(bmp))
    {
        g.DrawString(i.ToString(), 
                     new Font("Arial", 40), 
                     Brushes.Black, 
                     new PointF(400,1000));   
    }
    imageList.Add(bmp);
}

But I get an error when reading from this image list: Parameter is not valid. What am I doing wrong?

Answer 1

The bitmap is going to be destroyed by the using scope before it’s put into your list. Remove the using.

using will call Dispose on your image, which will invalidate the object. So, when you put it in the List you’re putting in a dead object.

List<Image> imageList = new List<Image>();
for (int i = 1; i <= totalCount; i++)    
{
        Bitmap bmp = new Bitmap(800,2000))
        using (Graphics g = Graphics.FromImage(bmp))
        {
            g.DrawString(i.ToString(), new Font("Arial", 40), Brushes.Black, new PointF(400,1000));   
        }

        imageList.Add(bmp);
}