解锁功能目标

Question

I have a Dictionary of byte[], Func as below:

 public class ImageSizeReader : IDisposable
 {

    private Dictionary<byte[], Func<BinaryReader, Size>> imageFormatDecoders;

    public ImageSizeReader()
    {
        imageFormatDecoders = new Dictionary<byte[], Func<BinaryReader, Size>>()
        {
            { new byte[] { 0x42, 0x4D }, DecodeBitmap },
            { new byte[] { 0x47, 0x49, 0x46, 0x38, 0x37, 0x61 }, DecodeGif },
            { new byte[] { 0x47, 0x49, 0x46, 0x38, 0x39, 0x61 }, DecodeGif },
            { new byte[] { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A }, DecodePng },
            { new byte[] { 0xff, 0xd8 }, DecodeJfif }};
    }

    private Size DecodeBitmap(BinaryReader binaryReader)
    {
    ....
    }

    private Size DecodeGif(BinaryReader binaryReader)
    {
        ...
    }

    private Size DecodePng(BinaryReader binaryReader)
    {
      ...
    }

    private Size DecodeJfif(BinaryReader binaryReader)
    {
       ...
    }

}

After using Memory Profiler I notice that this Dictionary is preventing garbage collection on it's parent class:

I am assuming it is because the Func delegate is still wired up. How would I 'unhook' this delegate list correctly?

Answer 1

I came back to this and eventually found that the code in the image above was compiler generated from a linq statement:

int maxMagicBytesLength = imageFormatDecoders.Keys.OrderByDescending(x => x.Length).First().Length;

I removed this method and did the same in a foreach loop which resolved the issue.