异步上传

public const int CHUNK_SIZE = 4096;  
public const string UPLOAD_URI = "http://localhost:55087/FileUpload.ashx?filename={0}&append={1}";  
private Stream _data;  
private string _fileName;  
private long 
_bytesTotal;  
private long _bytesUploaded;    
private void UploadFileChunk()  
{ 
    string uploadUri = ""; // Format the upload URI according to wether the it's the first chunk of the file 
    if (_bytesUploaded == 0) 
    { 
        uploadUri = String.Format(UPLOAD_URI,_fileName,0); // Dont't append 
    } 
    else if (_bytesUploaded < _bytesTotal) 
    { 
        uploadUri = String.Format(UPLOAD_URI, _fileName, 1); // append 
    } 
    else 
    { 
        return;  // Upload finished 
    } 
 
    byte[] fileContent = new byte[CHUNK_SIZE]; 
    _data.Read(fileContent, 0, CHUNK_SIZE); 
 
    WebClient wc = new WebClient(); 
    wc.OpenWriteCompleted += new OpenWriteCompletedEventHandler(wc_OpenWriteCompleted); 
    Uri u = new Uri(uploadUri); 
    wc.OpenWriteAsync(u, null, fileContent); 
    _bytesUploaded += fileContent.Length;  
}    
 
void wc_OpenWriteCompleted(object sender, OpenWriteCompletedEventArgs e)  
{ 
    if (e.Error == null) 
    {    
        object[] objArr = e.UserState as object[]; 
        byte[] fileContent = objArr[0] as byte[]; 
        int bytesRead = Convert.ToInt32(objArr[1]); 
        Stream outputStream = e.Result; 
        outputStream.Write(fileContent, 0, bytesRead); 
        outputStream.Close(); 
        if (_bytesUploaded < _bytesTotal) 
        { 
            UploadFileChunk(); 
        } 
        else 
        { 
            // Upload complete 
        } 
    }  
} 

　　

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