C# Stream.Copyto相关问题

Question

我获取一个图片流，然后想赋值给BitmapImage变量用于绑定。

发现用以下代码，直接赋值是无效的

MemoryStream ms = new MemoryStream();
Stream responseStream = GetSteamResponse(url);
responseStream.CopyTo(ms);
BitmapImage image = new BitmapImage();
image.BeginInit();
image.StreamSource = ms;
image.EndInit();
return image;

需要先把流转成字节数组，然后再用这个数组new一个新的MemeryStream赋值才能成功

MemoryStream ms = new MemoryStream();
Stream responseStream = GetSteamResponse(url);
responseStream.CopyTo(ms);
byte[] bytes = ms.GetBuffer();
ms.Close();
BitmapImage image = new BitmapImage();
image.BeginInit();
image.StreamSource = new MemoryStream(bytes);
image.EndInit();
return image;

copyto的流和new出来的有什么区别，为什么会造成这种情况？

Answer 1

你好,

可以直接赋值的，不过需要把memory.Position 设为0, 下面的代码，你可以参考一下。

using (MemoryStream memory = new MemoryStream())
            {
                Stream stream = GetSteamResponse(url);
                stream.CopyTo(memory);
                BitmapImage bitmapimage = new BitmapImage();
                stream.Close();
                memory.Position = 0;
                bitmapimage.BeginInit();
                bitmapimage.CacheOption = BitmapCacheOption.OnLoad;
                bitmapimage.StreamSource = memory;
                bitmapimage.EndInit();
                return bitmapimage;
 }

Best regards,

Zhanglong

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