How Can I Prevent File Access Errors When Updating PictureBox Images?

Maintain file access when modifying PictureBox images

In desktop applications, modifying a PictureBox's image using the new Bitmap() constructor may cause a file access error if the original image file is already in use. This problem occurs when the PictureBox keeps a reference to the initial file, preventing access to the file when a new image is loaded.

To solve this problem, a memory-friendly way is to use File.ReadAllBytes() to load the image into a MemoryStream and then use Image.FromStream() to create a new image. This way, the original file will be unlocked while allowing you to display the new image in the PictureBox without file access violations.

The following is a modified code example:

public static Image FromFile(string path)
{
    byte[] bytes = File.ReadAllBytes(path);
    using (MemoryStream ms = new MemoryStream(bytes))
    {
        Image img = Image.FromStream(ms);
        return img;
    }
}

pbAvatar.Image = FromFile(filePath);

This method not only solves the file access problem, but also improves performance. Testing has shown that loading images using this technique takes about 0.26 milliseconds per image, while copying from a bitmap takes about 0.50 milliseconds per image. The smaller memory footprint of byte arrays and the single image creation operation contribute to efficiency.

Please note that if the generated image needs to be a Bitmap object, you can use (Bitmap)Image.FromStream(ms) to convert the returned Image. In order to ensure the correct release of resources, we use the using statement to manage MemoryStream.

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