C# 使用Windows.Web.Http将文件从UWP应用上载到WebAPI Web服务

我的Windows 10 UWP应用程序正在调用我创建的WebAPI web服务。我需要从UWP应用程序向服务器发送一个JPG文件，以便服务器可以将其存储到另一个应用程序中

我正在使用

使用Windows.Web.Http

推荐用于UWP并使用Windows身份验证连接到服务器

当我使用以下代码执行POST时，我得到irandomaccesstream不支持GetInputStreamAt方法，因为它需要克隆错误，如下所示

我能够将

HttpStringContent

发布到同一个web服务上，并在没有任何问题的情况下收到回复

问题在于尝试使用

HttpStreamContent

将文件发送到web服务时

public async void Upload_FileAsync(string WebServiceURL, string FilePathToUpload)
{

    //prepare HttpStreamContent
    IStorageFile storageFile = await StorageFile.GetFileFromPathAsync(FilePathToUpload);
    IBuffer buffer = await FileIO.ReadBufferAsync(storageFile);
    byte[] bytes = System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeBufferExtensions.ToArray(buffer);
    Stream stream = new MemoryStream(bytes);
    Windows.Web.Http.HttpStreamContent streamContent = new Windows.Web.Http.HttpStreamContent(stream.AsInputStream());


    //send request
    var myFilter = new Windows.Web.Http.Filters.HttpBaseProtocolFilter();
    myFilter.AllowUI = false;
    var client = new Windows.Web.Http.HttpClient(myFilter);
    Windows.Web.Http.HttpResponseMessage result = await client.PostAsync(new Uri(WebServiceURL), streamContent);
    string stringReadResult = await result.Content.ReadAsStringAsync();

}

完全错误：

{System.NotSupportedException:此IRandomaccesstream不支持GetInputStreamAt方法，因为它需要克隆，而此流不支持克隆。 在System.IO.NetFxToWinRtStreamAdapter.throwcloningnotsupported处（字符串方法名） 在System.IO.NetFxToWinRtStreamAdapter.GetInputStreamAt处（UInt64位置） ---来自引发异常的上一个位置的堆栈结束跟踪--- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess（任务任务） 在System.Runtime.CompilerServices.TaskWaiter.HandleNonSuccessAndDebuggerNotification（任务任务）中 在System.Runtime.CompilerServices.TaskAwaiter`1.GetResult（）中 at}

---

请帮忙

获取文件并开始创建

HttpStreamContent

实例后，可以尝试使用该方法获取

irandomaccesstream

对象，然后将其作为

HttpStreamContent

对象构造函数参数

代码是这样的，你可以试试

public async void Upload_FileAsync(string WebServiceURL, string FilePathToUpload)
{

    //prepare HttpStreamContent
    IStorageFile storageFile = await StorageFile.GetFileFromPathAsync(FilePathToUpload);

    //Here is the code we changed
    IRandomAccessStream stream=await storageFile.OpenAsync(FileAccessMode.Read);
    Windows.Web.Http.HttpStreamContent streamContent = new Windows.Web.Http.HttpStreamContent(stream);

    //send request
    var myFilter = new Windows.Web.Http.Filters.HttpBaseProtocolFilter();
    myFilter.AllowUI = false;
    var client = new Windows.Web.Http.HttpClient(myFilter);
    Windows.Web.Http.HttpResponseMessage result = await client.PostAsync(new Uri(WebServiceURL), streamContent);
    string stringReadResult = await result.Content.ReadAsStringAsync();
}

在Web API控制器中

public IHostingEnvironment _environment;
public UploadFilesController(IHostingEnvironment environment) // Create Constructor 
{
    _environment = environment;
}

[HttpPost("UploadFiles")]
public Task<ActionResult<string>> UploadFiles([FromForm]List<IFormFile> allfiles)
{
    string filepath = "";
    foreach (var file in allfiles)
    {
        string extension = Path.GetExtension(file.FileName);
        var upload = Path.Combine(_environment.ContentRootPath, "FileFolderName");
        if (!Directory.Exists(upload))
        {
            Directory.CreateDirectory(upload);
        }
        string FileName = Guid.NewGuid() + extension;
        if (file.Length > 0)
        {
            using (var fileStream = new FileStream(Path.Combine(upload, FileName), FileMode.Create))
            {
                file.CopyTo(fileStream);
            }
        }
        filepath = Path.Combine("FileFolderName", FileName);
    }
    return Task.FromResult<ActionResult<string>>(filepath);
}

希望这段代码能帮助你

但是请记住

formContent.Add（fileContent，“allfiles”，file.Name）行很重要，
allfiles
是在web api方法中获取文件的参数名
“公共任务上载文件（[FromForm]列表**allfiles**）”

谢谢
 谢谢你的回复！这段代码消除了这个错误。但是，WebAPI web服务端上的函数捕获此调用的样子是什么？我尝试了
public async Task uploadDocumentsSync（byte[]fileUploadRequest）
和
public async Task uploadDocumentsSync（[FromBody]byte[]fileUploadRequest）
，也尝试了
IFormFile
的方法，但它没有捕获随此调用发送的请求。请帮忙！请看这里的其他问题：谢谢你的帮助！！
using Windows.Storage;
using Windows.Storage.Pickers;
.....
StorageFile file;
......

private async void btnFileUpload_Click(object sender, RoutedEventArgs e) // Like Browse button 
{
    try
    {
        FileOpenPicker openPicker = new FileOpenPicker();
        openPicker.ViewMode = PickerViewMode.Thumbnail;
        openPicker.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
        openPicker.FileTypeFilter.Add(".pdf");
        file = await openPicker.PickSingleFileAsync();
        if (file != null)
        {
            //fetch file details
        }
    }
    catch (Exception ex)
    {

    }
}

//When upload file
var http = new HttpClient();
var formContent = new HttpMultipartFormDataContent();
var fileContent = new HttpStreamContent(await file.OpenReadAsync());
formContent.Add(fileContent, "allfiles", file.Name);
var response = await http.PostAsync(new Uri("Give API Path" + "UploadFiles", formContent);
string filepath = Convert.ToString(response.Content); //Give path in which file is uploaded