53

在 Windows 8 中；我想将 MemoryStream 的内容传递给接受 Windows.Storage.Streams.IRandomAccessStream 类型参数的类。有没有办法将此 MemoryStream 转换为 IRandomAccessStream？

4

7 回答 7

98

要使用扩展：您必须添加“使用 System.IO”

在 Windows8 中，.NET 和 WinRT 类型通常在后台转换为兼容类型/从兼容类型转换，因此您不必关心它。

但是，对于流，有一些帮助方法可以在 WinRT 和 .NET 流之间进行转换：对于从 WinRT 流 -> .NET 流进行转换：

InMemoryRandomAccessStream win8Stream = GetData(); // Get a data stream from somewhere.
System.IO.Stream inputStream = win8Stream.AsStream()

从 .NET 流转换 -> WinRT 流：

Windows.Storage.Streams.IInputStream inStream = stream.AsInputStream();
Windows.Storage.Streams.IOutputStream outStream = stream.AsOutputStream();

更新：2013-09-01

不要说微软不听它的开发者社区；）

在.NET FX 4.5.1 的公告中，微软声明：

你们中的许多人一直想要一种将 .NET 流转换为 Windows 运行时 IRandomAccessStream 的方法。让我们称之为 AsRandomAccessStream 扩展方法。我们无法将此功能添加到 Windows 8 中，但它是我们首次添加到 Windows 8.1 Preview 中的功能之一。

您现在可以编写以下代码，使用 HttpClient 下载图像，将其加载到 BitmapImage 中，然后设置为 Xaml Image 控件的源。

    //access image via networking i/o
    var imageUrl = "http://www.microsoft.com/global/en-us/news/publishingimages/logos/MSFT_logo_Web.jpg";
    var client = new HttpClient();
    Stream stream = await client.GetStreamAsync(imageUrl);
    var memStream = new MemoryStream();
    await stream.CopyToAsync(memStream);
    memStream.Position = 0;
    var bitmap = new BitmapImage();
    bitmap.SetSource(memStream.AsRandomAccessStream());
    image.Source = bitmap;

HTH。

于 2011-10-13T18:42:21.773 回答
7

找到了一个更优雅的解决方案： 

public static class MicrosoftStreamExtensions
{
    public static IRandomAccessStream AsRandomAccessStream(this Stream stream)
    {
        return new RandomStream(stream);
    }

}

class RandomStream : IRandomAccessStream
{
    Stream internstream;

    public RandomStream(Stream underlyingstream)
    {
        internstream = underlyingstream;
    }

    public IInputStream GetInputStreamAt(ulong position)
    {
        //THANKS Microsoft! This is GREATLY appreciated!
        internstream.Position = (long)position;
        return internstream.AsInputStream();
    }

    public IOutputStream GetOutputStreamAt(ulong position)
    {
        internstream.Position = (long)position;
        return internstream.AsOutputStream();
    }

    public ulong Size
    {
        get
        {
            return (ulong)internstream.Length;
        }
        set
        {
            internstream.SetLength((long)value);
        }
    }

    public bool CanRead
    {
        get { return this.internstream.CanRead; }
    }

    public bool CanWrite
    {
        get { return this.internstream.CanWrite; }
    }

    public IRandomAccessStream CloneStream()
    {
        throw new NotSupportedException();
    }

    public ulong Position
    {
        get { return (ulong)this.internstream.Position; }
    }

    public void Seek(ulong position)
    {
        this.internstream.Seek((long)position, SeekOrigin.Begin);
    }

    public void Dispose()
    {
        this.internstream.Dispose();
    }

    public Windows.Foundation.IAsyncOperationWithProgress ReadAsync(IBuffer buffer, uint count, InputStreamOptions options)
    {
        return this.GetInputStreamAt(this.Position).ReadAsync(buffer, count, options);
    }

    public Windows.Foundation.IAsyncOperation FlushAsync()
    {
        return this.GetOutputStreamAt(this.Position).FlushAsync();
    }

    public Windows.Foundation.IAsyncOperationWithProgress WriteAsync(IBuffer buffer)
    {
        return this.GetOutputStreamAt(this.Position).WriteAsync(buffer);
    }
}
于 2011-10-06T16:06:31.607 回答
5

经过一些试验，我发现以下代码可以正常工作。

using System;
using System.IO;
using System.Threading.Tasks;
using Windows.Storage.Streams;

partial class MainPage
{
    public MainPage()
    {
        var memoryStream = new MemoryStream(new byte[] { 65, 66, 67 });
        ConvertToRandomAccessStream(memoryStream, UseRandomAccessStream);
        InitializeComponent();
    }

    void UseRandomAccessStream(IRandomAccessStream stream)
    {
        var size = stream.Size;
    } // put breakpoint here to check size

    private static async void ConvertToRandomAccessStream(MemoryStream memoryStream,
         Action<IRandomAccessStream> callback)
    {
        var randomAccessStream = new InMemoryRandomAccessStream();
        var outputStream = randomAccessStream.GetOutputStreamAt(0);
        var dw = new DataWriter(outputStream);
        var task = new Task(() => dw.WriteBytes(memoryStream.ToArray()));
        task.Start();
        await task;
        await dw.StoreAsync();
        var success = await outputStream.FlushAsync();
        callback(randomAccessStream);
    }
}

更新：我还尝试了更优雅的方法实现：

    private static void ConvertToRandomAccessStream(MemoryStream memoryStream,
        Action<IRandomAccessStream> callback)
    {
        var randomAccessStream = new InMemoryRandomAccessStream();
        var outputStream = randomAccessStream.GetOutputStreamAt(0);
        RandomAccessStream.Copy(memoryStream.AsInputStream(), outputStream);
        callback(randomAccessStream);
    }

奇怪的是，它不起作用。当我stream.Size稍后打电话时，我得到零。

更新我更改了函数以返回 IRandomAccessStream 而不是使用回调函数

public static async Task<IRandomAccessStream> ConvertToRandomAccessStream(MemoryStream memoryStream)
{
    var randomAccessStream = new InMemoryRandomAccessStream();

    var outputStream = randomAccessStream.GetOutputStreamAt(0);
    var dw = new DataWriter(outputStream);
    var task = new Task(() => dw.WriteBytes(memoryStream.ToArray()));
    task.Start();

    await task;
    await dw.StoreAsync();

    await outputStream.FlushAsync();

    return randomAccessStream;
}
于 2011-10-06T15:53:10.457 回答
4

Windows 8 上没有内置方式方法。对于 Windows 8.1，我们添加了 Stream.AsRandomAccessStream() 扩展方法：

internal static IRandomAccessStream ToRandomAccessStream(byte[] array)
{
    MemoryStream stream = new MemoryStream(array);
    return stream.AsRandomAccessStream();
}
于 2013-06-28T00:21:11.020 回答
3

今天以上都不适用于我（可能在发布答案后发生了一些 API 更改）。唯一可行的方法是

IRandomAccessStream inMemoryStream = new InMemoryRandomAccessStream();
using (var inputStream = stream.AsInputStream())
{
    await RandomAccessStream.CopyAsync(inputStream, inMemoryStream);
}
inMemoryStream.Seek(0);
于 2013-03-12T10:17:06.900 回答
0

此代码片段将流 ( stream) 转换为 InMemoryRandomAccessStream( ims) 实现IRandomAccessStream。诀窍是必须在后台线程上调用 CopyTo。

        InMemoryRandomAccessStream ims = new InMemoryRandomAccessStream();
        var imsWriter = ims.OpenWrite();
        await Task.Factory.StartNew(() => stream.CopyTo(imsWriter));
于 2011-11-14T16:46:28.097 回答
0

看看这个链接：

如何将字节数组转换为 IRandomAccessStream

它还提供了字节数组构造函数的示例和实现（以及一个用于 .NET 流的构造函数），如果您想使用类的SetSourceorSetSourceAsync方法BitmapImage（如我的例子），这很有用。

希望这可以帮助某人...

于 2013-08-28T08:17:30.980 回答