将PushStreamContent C#代码转换为VB.Net WebAPI 2时出错

本文关键字：Net WebAPI 2时 出错 VB PushStreamContent 代码 转换 | 更新日期: 2023-09-27 18:29:05

我在将这段C#代码转换为WebAPI 2 VB.Net项目时遇到了一些困难。

这是原始的C#代码

[HttpGet]
public HttpResponseMessage FromImages() {
    var imageStream = new ImageStream();
    Func<Stream, HttpContent, TransportContext, Task> func = imageStream.WriteToStream;
    var response = Request.CreateResponse();
    response.Content = new PushStreamContent(func);
    response.Content.Headers.Remove("Content-Type");
    response.Content.Headers.TryAddWithoutValidation("Content-Type", "multipart/x-mixed-replace;boundary=" + imageStream.Boundary);
    return response;
}
internal class ImageStream {
    public object Boundary { get; private set; } = "HintDesk";
    public async Task WriteToStream(Stream outputStream, HttpContent content, TransportContext context) {
        byte[] newLine = Encoding.UTF8.GetBytes("'r'n");
        foreach (var file in Directory.GetFiles(@"TestData'Images", "*.jpg")) {
            var fileInfo = new FileInfo(file);
            var header = $"--{Boundary}'r'nContent-Type: image/jpeg'r'nContent-Length: {fileInfo.Length}'r'n'r'n";
            var headerData = Encoding.UTF8.GetBytes(header);
            await outputStream.WriteAsync(headerData, 0, headerData.Length);
            await fileInfo.OpenRead().CopyToAsync(outputStream);
            await outputStream.WriteAsync(newLine, 0, newLine.Length);
            await Task.Delay(1000 / 30);
        }
    }
}

这是VB.Net翻译的

    <HttpGet> _
    Public Function FromImages() As HttpResponseMessage
        Dim imageStream = New ImageStream()
        Dim func As Func(Of Stream, HttpContent, TransportContext, Task) = imageStream.WriteToStream
        Dim response = Request.CreateResponse()
        response.Content = New PushStreamContent(func)
        response.Content.Headers.Remove("Content-Type")
        response.Content.Headers.TryAddWithoutValidation("Content-Type", "multipart/x-mixed-replace;boundary=" + imageStream.Boundary)
        Return response
    End Function
    Friend Class ImageStream
        Public Function WriteToStream(outputStream As Stream, content As HttpContent, context As TransportContext) As Task
            Dim newLine As Byte() = Encoding.UTF8.GetBytes(vbCr & vbLf)
            For Each file As var In Directory.GetFiles("TestData'Images", "*.jpg")
                Dim fileInfo = New FileInfo(file)
                Dim header = "--{Boundary}" & vbCr & vbLf & "Content-Type: image/jpeg" & vbCr & vbLf & "Content-Length: {fileInfo.Length}" & vbCr & vbLf & vbCr & vbLf
                Dim headerData = Encoding.UTF8.GetBytes(header)
                Await outputStream.WriteAsync(headerData, 0, headerData.Length)
                Await fileInfo.OpenRead().CopyToAsync(outputStream)
                Await outputStream.WriteAsync(newLine, 0, newLine.Length)
                Await Task.Delay(1000 / 30)
            Next
        End Function
    End Class

我看到两个问题：

  1. 此行中有一个"Argument not specified for parameter"context"of"Public Function WriteToStream…"

    Dim func As func（Of Stream，HttpContent，TransportContext，Task）=imageStream。WriteToStream

  2. 重载解析失败，因为无法使用这些参数调用可访问的"New"

    response.Content=新建PushStreamContent（函数）

我想我没有正确地翻译这个，但我很难在VB.Net中找到我想要完成的任何例子。有人能告诉我我做错了什么吗？

将PushStreamContent C#代码转换为VB.Net WebAPI 2时出错

主要问题是您没有使用"AddressOf"-这是VB的等价物：

Option Infer On
Imports Microsoft.VisualBasic
<HttpGet>
Public Function FromImages() As HttpResponseMessage
    Dim imageStream = New ImageStream()
    Dim func As Func(Of Stream, HttpContent, TransportContext, Task) = AddressOf imageStream.WriteToStream
    Dim response = Request.CreateResponse()
    response.Content = New PushStreamContent(func)
    response.Content.Headers.Remove("Content-Type")
    response.Content.Headers.TryAddWithoutValidation("Content-Type", "multipart/x-mixed-replace;boundary=" & imageStream.Boundary)
    Return response
End Function
Friend Class ImageStream
    Private privateBoundary As Object = "HintDesk"
    Public Property Boundary() As Object
        Get
            Return privateBoundary
        End Get
        Private Set(ByVal value As Object)
            privateBoundary = value
        End Set
    End Property
    Public Async Function WriteToStream(ByVal outputStream As Stream, ByVal content As HttpContent, ByVal context As TransportContext) As Task
        Dim newLine() As Byte = Encoding.UTF8.GetBytes(ControlChars.CrLf)
        For Each file In Directory.GetFiles("TestData'Images", "*.jpg")
            Dim fileInfo = New FileInfo(file)
            Dim header = $"--{Boundary}" & ControlChars.CrLf & "Content-Type: image/jpeg" & ControlChars.CrLf & "Content-Length: {1}" & ControlChars.CrLf & ControlChars.CrLf
            Dim headerData = Encoding.UTF8.GetBytes(header)
            Await outputStream.WriteAsync(headerData, 0, headerData.Length)
            Await fileInfo.OpenRead().CopyToAsync(outputStream)
            Await outputStream.WriteAsync(newLine, 0, newLine.Length)
            Await Task.Delay(1000 ' 30)
        Next file
    End Function
End Class
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