如何解析包含多个文件的 XHR multipart/form-data 请求

Question

我在网上看到了 multipart/form-data 解析器的多个示例，但其中 none 可以在我的网站上运行。我正在使用 Kendo 上传控件设置为异步模式并启用批量上传，生成的请求如下所示：

BOUNDARY
Content-Disposition: form-data; name="Param_1"

Param_1 Value
BOUNDARY
Content-Disposition: form-data; name="Param_2"

Param_2 Value
BOUNDARY
Content-Disposition: form-data; name="files[]"; filename="A.docx"
Content-Type: application/octet-stream

[Binary Data Here]
BOUNDARY
Content-Disposition: form-data; name="files[]"; filename="B.docx"
Content-Type: application/octet-stream

[Binary Data Here]
BOUNDARY--

我在网上找到的每个库都成功地检索了参数和第一个文件，但有些库从来没有看到第二个，而那些确实保存不正确的库。 SO WCF multipart/form data with multiple files 上有一个类似的问题，但该解决方案仅适用于文本文件而不适用于二进制文件。

Answer 1

其他解决方案对二进制文件的问题是它们将响应转换为字符串进行解析，然后将该字符串转换回文件，这不适用于二进制数据。我想出了一个解决方案，我没有将响应转换为字符串来解析它，而是将其保留为 byte[]，并使用找到的代码 here 通过分隔符将其拆分为 byte[]。完成后将每个片段转换为字符串以查看它是参数还是文件，如果是参数则读取它，否则将其写入文件。这是工作代码，假设您将 Stream 作为 byte[] 并将分隔符作为字符串：

// given byte[] streamByte, String delimiterString, and Encoding encoding
Regex regQuery;
Match regMatch;
string propertyType;

byte[] delimiterBytes = encoding.GetBytes(delimiterString);
byte[] delimiterWithNewLineBytes = encoding.GetBytes(delimiterString + "\r\n");
// the request ends DELIMITER--\r\n
byte[] delimiterEndBytes = encoding.GetBytes("\r\n" + delimiterString + "--\r\n");
int lengthDifferenceWithEndBytes = (delimiterString + "--\r\n").Length;

// seperate by delimiter + newline
// ByteArraySplit code found at 
byte[][] separatedStream = ByteArraySplit(streamBytes, delimiterWithNewLineBytes);
streamBytes = null;
for (int i = 0; i < separatedStream.Length; i++)
{
    // parse out whether this is a parameter or a file
    // get the first line of the byte[] as a string
    string thisPieceAsString = encoding.GetString(separatedStream[i]);

    if (string.IsNullOrWhiteSpace(thisPieceAsString)) { continue; }

    string firstLine = thisPieceAsString.Substring(0, thisPieceAsString.IndexOf("\r\n"));

    // Check the item to see what it is
    regQuery = new Regex(@"(?<=name\=\"")(.*?)(?=\"")");
    regMatch = regQuery.Match(firstLine);
    propertyType = regMatch.Value.Trim();

    // get the index of the start of the content and the end of the content
    int indexOfStartOfContent = thisPieceAsString.IndexOf("\r\n\r\n") + "\r\n\r\n".Length;

    // this line compares the name to the name of the html input control, 
    // this can be smarter by instead looking for the filename property
    if (propertyType != "files")
    {
        // this is a parameter!
        // if this is the last piece, chop off the final delimiter
        int lengthToRemove = (i == separatedStream.Length - 1) ? lengthDifferenceWithEndBytes : 0;
        string value = thisPieceAsString.Substring(indexOfStartOfContent, thisPieceAsString.Length - "\r\n".Length - indexOfStartOfContent - lengthToRemove);
        // do something with the parameter
    }
    else
    {
        // this is a file!
        regQuery = new Regex(@"(?<=filename\=\"")(.*?)(?=\"")");
        regMatch = regQuery.Match(firstLine);
        string fileName = regMatch.Value.Trim();

        // get the content byte[]
        // if this is the last piece, chop off the final delimiter
        int lengthToRemove = (i == separatedStream.Length - 1) ? delimiterEndBytes.Length : 0;
        int contentByteArrayStartIndex = encoding.GetBytes(thisPieceAsString.Substring(0, indexOfStartOfContent)).Length;
        byte[] fileData = new byte[separatedStream[i].Length - contentByteArrayStartIndex - lengthToRemove];
        Array.Copy(separatedStream[i], contentByteArrayStartIndex, fileData, 0, separatedStream[i].Length - contentByteArrayStartIndex - lengthToRemove);
        // save the fileData byte[] as the file
    }

}

如何解析包含多个文件的 XHR multipart/form-data 请求

How to parse XHR multipart/form-data request with multiple files

c#

wcf

kendo-upload