c# - 'system.argumentexception' 上传多部分时

Question

我正在尝试使用 System.Net.Http.HttpClient 发布多部分数据，但是当我实例化我的内容时出现此异常:

A first chance exception of type 'System.ArgumentException' occurred in System.Net.Http.DLL
An exception of type 'System.ArgumentException' occurred in System.Net.Http.DLL and wasn't handled before a managed/native boundary
e: System.ArgumentException: The format of value '---###---' is invalid.
Parameter name: boundary
   at System.Net.Http.MultipartContent.ValidateBoundary(String boundary)
   at System.Net.Http.MultipartContent..ctor(String subtype, String boundary)
   at System.Net.Http.MultipartFormDataContent..ctor(String boundary)
   at RestClientUploadFoto.MultipartStackOverflow.<postMultipart>d__2.MoveNext()

• 为什么会这样？

这是我得到异常的方法:

public async Task postMultipart()
{
    var client = new HttpClient();
    client.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type", "multipart/form-data");

    // boundary      
    String boundary = "---###---"; // should never occur in your data

    // This is the postdata
    MultipartFormDataContent content = new MultipartFormDataContent(boundary);
    content.Add(new StringContent("12", Encoding.UTF8), "userId");
    content.Add(new StringContent("78", Encoding.UTF8), "noOfAttendees");
    content.Add(new StringContent("chennai", Encoding.UTF8), "locationName");
    content.Add(new StringContent("32.56", Encoding.UTF8), "longitude");
    content.Add(new StringContent("32.56", Encoding.UTF8), "latitude");

    Console.Write(content);
    // upload the file sending the form info and ensure a result.
    // it will throw an exception if the service doesn't return a valid successful status code
    await client.PostAsync(fileUploadUrl, content)
        .ContinueWith((postTask) =>
        {
            postTask.Result.EnsureSuccessStatusCode();
        });

}

Answer 1

# 在 MIME 边界中无效。

来自 RFC 2046 :

The only mandatory global parameter for the "multipart" media type isthe boundary parameter, which consists of 1 to 70 characters from aset of characters known to be very robust through mail gateways, andNOT ending with white space. (If a boundary delimiter line appears toend with white space, the white space must be presumed to have beenadded by a gateway, and must be deleted.) It is formally specifiedby the following BNF:

boundary := 0*69<bchars> bcharsnospace

bchars := bcharsnospace / " "

bcharsnospace := DIGIT / ALPHA / "'" / "(" / ")" /
                 "+" / "_" / "," / "-" / "." /
                 "/" / ":" / "=" / "?"

所以基本上，您应该使用不包含 # 的边界字符串。我建议使用也不包含连字符的连字符，因为边界 行 无论如何都会有连字符(在开始和结束处)。将它们也放在边界中有点令人困惑。

除非您需要特定边界，否则我建议您只调用无参数构造函数，它将使用随机 GUID 作为边界。