上传图片更新

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.IO;
namespace Web
{
    public class Post
    {
        public static string HttpUploadFile(string id, string token, string filepath)
        {

            // 这个可以是改变的，也可以是下面这个固定的字符串 
            string boundary = "c808bb4d-264c-4484-bb95-11d72a277878";
            string url = "https://api.domain.cc/User.updateAvatar";

            // 创建request对象 
            HttpWebRequest webrequest = (HttpWebRequest)WebRequest.Create(url);
            webrequest.ContentType = "multipart/form-data; boundary=" + boundary;
            webrequest.Method = "POST";
            webrequest.UserAgent = "okhttp-okgo/jeasonlzy";

            // 构造发送数据
            StringBuilder sb = new StringBuilder();

            // 文本域的数据
            sb.Append("--" + boundary);
            sb.Append("
");
            sb.Append("Content-Disposition: form-data; name="uid"");
            sb.Append("
");
            sb.Append("Content-Length: 6");
            sb.Append("

");
            sb.Append(id);
            sb.Append("
");


            // 文件域的数据
            sb.Append("--" + boundary);
            sb.Append("
");
            sb.Append("Content-Disposition: form-data; name="token"");
            sb.Append("
");
            sb.Append("Content-Length: 32");
            sb.Append("

");
            sb.Append(token);
            sb.Append("
");
            sb.Append("--" + boundary);
            sb.Append("
");
            sb.Append("Content-Disposition: form-data; name="file"; filename="20200205162320.png"");
            sb.Append("
");
            sb.Append("Content-Type: image/png");
            //少length ？？？
            sb.Append("

");

            string postHeader = sb.ToString();
            byte[] postHeaderBytes = Encoding.UTF8.GetBytes(postHeader);

            //构造尾部数据 
            byte[] boundaryBytes = Encoding.ASCII.GetBytes("
--" + boundary + "--
");

            FileStream fileStream = new FileStream(filepath, FileMode.Open, FileAccess.Read);
            long length = postHeaderBytes.Length + fileStream.Length + boundaryBytes.Length;
            webrequest.ContentLength = length;

            Stream requestStream = webrequest.GetRequestStream();

            // 输入头部数据 
            requestStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);

            // 输入文件流数据 
            byte[] buffer = new Byte[checked((uint)Math.Min(4096, (int)fileStream.Length))];
            int bytesRead = 0;
            while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
                requestStream.Write(buffer, 0, bytesRead);

            // 输入尾部数据 
            requestStream.Write(boundaryBytes, 0, boundaryBytes.Length);
            WebResponse responce = webrequest.GetResponse();
            Stream s = responce.GetResponseStream();
            StreamReader sr = new StreamReader(s);

            // 返回数据流(源码) 
            return sr.ReadToEnd();
        }
    }
}

$filePath='E:1.png'
$url='https://api.domain.cc/updateAvatar'
$fileBin=[System.IO.File]::ReadAllBytes($filePath)
$en=[System.Text.Encoding]::GetEncoding("iso-8859-1")
$fileEnc=$en.GetString($fileBin)
$boundary=[System.Guid]::NewGuid().toString()
$lf="`r`n"
$bodyLines=(
    "--$boundary",
    "Content-Disposition: form-data; name=`"uid`"",
    "Content-Length: 6$lf",
    "310413",
    "--$boundary",
    "Content-Disposition: form-data; name=`"token`"",
    "Content-Length: 32$lf",
    "5aea7d9dbd15de0fd8b7e26fd8220e8b",
    "--$boundary",
    "Content-Disposition: form-data; name=`"file`"; filename=`"20200205162320.png`"",
    "Content-Type: image/png$lf",
    $fileEnc,
    "--$boundary--$lf"
) -join $lf

$r=Invoke-RestMethod -Uri $url -Method Post -ContentType "multipart/form-data; boundary=$boundary" -UserAgent "okhttp-okgo/jeasonlzy" -Body $bodyLines

补充：注意字节的编码方式 不然即使图片上传成功了 也无法正常显示