How to dispose bitmap

[lufuguo]

public D2D.Bitmap LoadBitmapFromFile(String filename,int frameIndex = 0)
{
D2D.Bitmap bitmap = null;
NativeFileStream fileStream = new NativeFileStream(filename, NativeFileMode.Open, NativeFileAccess.Read);
BitmapDecoder bitmapDecoder = new BitmapDecoder(_imagingFactory, fileStream, DecodeOptions.CacheOnDemand);
BitmapFrameDecode frame = bitmapDecoder.GetFrame(0);
FormatConverter converter = new FormatConverter(_imagingFactory);
converter.Initialize(frame, SharpDX.WIC.PixelFormat.Format32bppPRGBA);

        bitmap = SharpDX.Direct2D1.Bitmap1.FromWicBitmap(_renderTarget, converter);
        return bitmap;
    }

When I load bitmap from file continuous using this code ,memory increase all the time . [Bitmap object] dispose function have no effect, [GC.Collect] have no effect also.This [Bitmap object] how to dispose.Help me please.

[mrvux]

There are quite a lot of other variables in your function that are also disposable, so enclosing those in "using directive" will help:

using (NativeFileStream fileStream = new NativeFileStream(filename, NativeFileMode.Open, NativeFileAccess.Read))
        {
            
using (BitmapDecoder bitmapDecoder = new BitmapDecoder(imagingFactory, fileStream, DecodeOptions.CacheOnDemand))
            {
                using (BitmapFrameDecode frame = bitmapDecoder.GetFrame(frameIndex))
                {
                    using (FormatConverter converter = new FormatConverter(imagingFactory))
                    {
                        converter.Initialize(frame, SharpDX.WIC.PixelFormat.Format32bppPRGBA);
                        return SharpDX.Direct2D1.Bitmap1.FromWicBitmap(dc, converter);
                    }
                }
            }
        } `