Question

Using Visual C# 2008 Exp Edition, I’ve noticed that with my project loaded the process is consuming ~70,000K of memory. After a few hours this builds up to about ~500,000K.

At this point a UserControl containing a PictureBox (within a Panel) shows a memory error in Visual C# Express. The picture box contains a bitmap and grid of rectangles, drawn with System.Drawing.Graphics.

Here’s the code:

This segement occurs just once when the UserControl is initialised.

Bitmap myBitmap = new Bitmap(a, b);
Graphics g = null;
g = Graphics.FromImage(myBitmap);
g.FillRectangle(Brushes.SteelBlue, 0, 0, c, d);

//Paint Rows & Columns
for (int x = 0; x <= e - 1; x++)
{
    for (int y = 0; y <= f - 1; y++)
    {
        g.DrawRectangle(Pens.LightBlue, g, h, i);
    }
}
//Release Resources
g.Dispose();
//Add bitmap with grid to BG
ScorePictureBox.Image = myBitmap;

This piece of code is quite frequent:

for (int EventIndex = 0; EventIndex <= MidiNoteDownArray.Length - 1; EventIndex++)
{
    //Paint notes to grid

    e.Graphics.FillRectangle(Brushes.LightBlue, j, k, l, m);
    e.Graphics.DrawRectangle(Pens.Purple, o, p, q, r);
}
e.Dispose();

Am I not releasing resources properly? How can I do this correctly?

Answer 1

You’re not releasing your bitmap. Depending on how often your code runs the garbage collector may not be able to keep up.

using (Bitmap myBitmap = new Bitmap(a, b))
using (Graphics g = Graphics.FromImage(myBitmap)) {
    for (int x = 0; x <= e - 1; x++) {
        for (int y = 0; y <= f - 1; y++) {
            g.DrawRectangle(Pens.LightBlue, g, h, i);
        }
    }

    ScorePictureBox.Image = myBitmap;
}

You will want to check other parts of your code that use GDI for unreleased resources as well.