C#: Why am I getting "the process cannot access the file * because it is being used by another process" with this code?

Question

I'm trying to convert bmp files in a folder to jpg, then delete the old files. The code works fine, except it can't delete the bmp's.

DirectoryInfo di = new DirectoryInfo(args[0]);
FileInfo[] files = di.GetFiles("*.bmp");
foreach (FileInfo file in files)
{
    string newFile = file.FullName.Replace("bmp", "jpg");
    Bitmap bm = (Bitmap)Image.FromFile(file.FullName);
    bm.Save(newFile, ImageFormat.Jpeg);
}
for (int i = 0; i < files.Length; i++)
    files[i].Delete();

The files aren't being used by another program/process like the error indicates, so I'm assuming the problem is here. But to me the code seems fine, since I'm doing everything sequentially. This is all that there is to the program too, so the error can't be caused by code elsewhere.

Answer 1

Try wrap bitmaps with using:

using (Bitmap bm = (Bitmap)Image.FromFile(file.FullName))
{
    bm.Save(newFile, ImageFormat.Jpeg);
}

This will dispose bitmap objects just after they were saved.

Answer 2

The best way to solve the issue with Image.FromFile wherein it leaves file handles open is to use Image.FromStream instead.

using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))
{
   using (Image original = Image.FromStream(fs))
   {
     ...

Using an explicit Dispose(), a using() statement or setting the value to null doesn't solve the issue until a garbage collection happens (and forcing a garbage collection to happen is generally a bad idea).

Answer 3

public static Image LoadImage( string fileFullName )
{
    Stream fileStream = File.OpenRead( fileFullName );
    Image image       = Image.FromStream( fileStream );

    // PropertyItems seem to get lost when fileStream is closed to quickly (?); perhaps
    // this is the reason Microsoft didn't want to close it in the first place.
    PropertyItem[] items = image.PropertyItems;

    fileStream.Close();

    foreach ( PropertyItem item in items )
    {
        image.SetPropertyItem( item );
    }

    return image;
}