StreamContent未加载结束

Question

我有（几）的WebAPI行动（S），其装载的QuickFix日志从数据库（通过EF），并使用该私有方法将其返回为CSV：

private HttpResponseMessage BuildCsvResponse<T>(T[] entries, Func<T, string> row, string fileName) 
{ 
    var response = new HttpResponseMessage(HttpStatusCode.OK); 
    var stream = new MemoryStream(); 
    var writer = new StreamWriter(stream); 
    var i = entries.Length; 
    foreach (var entry in entries) 
    { 
     i--; 
     writer.WriteLine(row(entry)); // simply call to overridden ToString() method 
    } 
    stream.Seek(0, SeekOrigin.Begin); 
    stream.Flush(); 
    response.Content = new StreamContent(stream); 
    response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment") 
    { 
     FileName = fileName, 
    }; 
    response.Content.Headers.ContentType = new MediaTypeHeaderValue("text/csv"); 
    return response; 
} 

的问题是，内容永远不会加载到末尾，并在随后的符号上截断不远。为什么会发生？

可能是很重要的 - 所有的日志字符串包含分隔符0x01

Answer 1

你需要你触摸底层流之前刷新你的StreamWriter的内部缓冲区。

最好是告诉你的StreamWriter通过使用另一个contructor来保持流打开。然后，您可以安全地处置您的Streamwriter，使其在您的内存流实例保持打开状态时刷新其缓冲区，并且不会丢弃。

请注意，您需要选择一个与您的HTTP内容响应相匹配的编码。我在这里选择UTF8，并相应地进行调整。

var stream = new MemoryStream(); 
// notice the true as last parameter, false is the default. 
using(var writer = new StreamWriter(stream, Encoding.UTF8, 8192, true)) 
{ 
    var i = entries.Length; 
    foreach (var entry in entries) 
    { 
     i--; 
     writer.WriteLine(row(entry)); // simply call to overridden ToString() method 
    } 
} 
// your streamwriter has now flushed its buffer and left the stream open 
stream.Seek(0, SeekOrigin.Begin); 
// calling Flush on the stream was never needed so I removed that. 
response.Content = new StreamContent(stream);