[求助] 用 IE 上传文件就差这一步了，报错（Required MultipartFile parameter 'file' is not present）

用下述代码，生成参数，发送请求头后，返回：{"code":501,"msg":"Required MultipartFile parameter 'file' is not present"}，求指导。

模拟提报代码：
sub Main（）
Dim FileName As String
FileName = "C:\Users\danl.txt"
With CreateObject("winhttp.winhttprequest.5.1")
.Open "POST", "https://datasource/localConnection/uploadFile", False
.setRequestHeader "Content-Type", "multipart/form-data; boundary=---------------------------1997060815188" '要与下面SendBody里的一致
.setRequestHeader "Accept-Encoding", "gzip, deflate, br"
.setRequestHeader "Cookie", MyCookie
.setRequestHeader "Connection", "Keep-Alive"
.send SendBody(FileName) '发送字串
Debug.Print .responseText '可以登录论坛到发帖页面查看是否有“未使用附件”
End With
end sub

参数生成代码：
Function SendBody(ByVal Fn As String)
Dim MyStr As String
Dim b() As Byte
Dim StrByte() As Byte
Dim sLen As Long

MyStr = "-----------------------------1997060815188" '系统产生的随机数字   '头部
MyStr = MyStr & vbCrLf & "Content-Disposition: form-data; name=""config""" & vbCrLf & vbCrLf & "%7B%22fileType%22%3A0%2C%22delimiter%22%3A0%7D"
MyStr = MyStr & vbCrLf & "-----------------------------1997060815188" '系统产生的随机数字   '头部
MyStr = MyStr & vbCrLf & "Content-Disposition: form-data; name=""file""; filename=""danl.csv"""
MyStr = MyStr & vbCrLf & "Content-Type: application/vnd.ms-excel" & vbCrLf
MyStr = MyStr & vbCrLf

' MsgBox MyStr
StrByte = StrConv(MyStr, vbFromUnicode128) '将之前的字符串转为byte

b = FileToByte(Fn) '将要上传的文件转为byte
'    合并字符串及文件成一个byte

Debug.Print b
sLen = UBound(StrByte)
ReDim Preserve StrByte(sLen + UBound(b) - 1)
For i = 2 To UBound(b)
    StrByte(sLen + i - 1) = b(i)
Next

MyStr = vbCrLf & "-----------------------------1997060815188--"  '结束多2杆
MyStr = MyStr & vbCrLf

' MsgBox MyStr
b = StrConv(MyStr, vbFromUnicode128)
' Debug.Print b

sLen = UBound(StrByte)
ReDim Preserve StrByte(sLen + UBound(b) + 1)
For i = 0 To UBound(b)
    StrByte(sLen + i + 1) = b(i)
Next

SendBody = StrByte
Debug.Print SendBody

End Function
Function FileToByte(ByVal Fn As String)

 With CreateObject("adodb.stream")
    .Open
    .LoadFromFile Fn
    .Charset = "GB2312"
    .Type = 1
    FileToByte = .Read
    .Close
End With

End Function