在Httpclient 上传文件时 需要显示进度，需要添加 ProgressMessageHandler 在NuGet中添加 引用
Microsoft.AspNet.WebApi.Client 一下是全部代码包括文件上传

private async void button2_Click(object sender, EventArgs e)
{
HttpClientHandler handler = new HttpClientHandler();
ProgressMessageHandler progressMessageHandler = new ProgressMessageHandler(handler);
progressMessageHandler.HttpSendProgress += ProgressMessageHandler_HttpSendProgress;
var httpClient = new HttpClient(progressMessageHandler);
httpClient.Timeout = Timeout.InfiniteTimeSpan;
var url = "http://10.141.40.176:5236/main/Uploadfile";
var content = new MultipartFormDataContent();
content.Add(new StringContent("ulami"), "Department");
content.Add(new StringContent("1"), "taskname");
content.Add(new StringContent("false"), "cover");
// StringContent loginContent = new StringContent("{\"username\":\"admin\",\"password\":\"123456\"}", Encoding.UTF8, "application/json");
var filepath = textBox1.Text;//97.6MB
using var fileStream = new FileStream(filepath, FileMode.Open, FileAccess.Read);
using var streamContent = new StreamContent(fileStream, 102400);
content.Add(streamContent, "file", "测试文件1.ppt");
var response = await httpClient.PostAsync(url, content);
var str = await response.Content.ReadAsStringAsync();
textBox2.Text = str;
// try
// {
// //上传服务器的地址（web服务）
// string address = "http://10.141.40.176:7245/main/dwj";
// //上传后文件保存的名称
// string saveName = DateTime.Now.ToString("yyyyMMddHHmmss");
// int count = FileUpload.UpLoad_Request(address, filePath, saveName,progressBar1);
// if (count > 0)
// {
// MessageBox.Show("上传文件成功！");
// }
// else
// {
// MessageBox.Show("上传文件失败！");
// }
// }
// catch (Exception ex)
// {

        //        Console.WriteLine(ex.Message);  
        //    }  
    }

    private void ProgressMessageHandler\_HttpSendProgress(object sender, HttpProgressEventArgs e)  
    {  
        Console.WriteLine(e.ProgressPercentage + "%");  
    }