C# 如何通过API从winform应用程序上传照片？

我有两个项目。一个是Windows窗体项目，另一个是.NET Core 2.0 Web API项目。我可以从Windows窗体应用程序调用我的Web API，并可以调用基本的CRUD操作

我需要贴张照片。我该怎么做？我的帖子是这样的：

private async void AddStudent()
{
    var p = new Student
    {
        FirstName = "Johdn",
        LastName = "Doe",
        Avatar = "Image"; // my photo
    };

    using (var client = new HttpClient())
    {
        var serializedStudent = JsonConvert.SerializeObject(p);
        var content = new StringContent(serializedStudent, Encoding.UTF8, "application/json");
        var result = await client.PostAsync(URI, content);
    }
}

Web API实现如下所示：

public void Post([FromBody] Student student)
{
    var insideStudent = _dbContext.Students.FirstOrDefault(cus => cus.Id == student.Id);
    if (insideStudent != null)
    {
        insideStudent.FirstName = student.FirstName;
        insideStudent.LastName = student.LastName;
        _dbContext.SaveChanges();
    } else {
        _dbContext.Students.Add(new Student
        {
            FirstName = student.FirstName,
            LastName = student.LastName,
            Avatar = student.Avatar // my photo
        });
        _dbContext.SaveChanges();
    }
}

---

但是如何将图像发送到我的Web API？

MultipartFormDataContent

可以是一个选项。假设

Student.Avatar

是一个字节数组：

public byte[] Avatar { get; set; }

并且您拥有图像的

流

，您可以将其作为字节数组内容与字符串内容一起发送：

    private async void AddStudent()
    {
        var stream = //gets image stream...
        var p = new Student
        {
            FirstName = "Johdn",
            LastName = "Doe",
        };
        using (var client = new HttpClient())
        {
            var serializedStudent = JsonConvert.SerializeObject(p);
            var stringContent = new StringContent(serializedStudent, Encoding.UTF8, "application/json");
            var multipartContent = new MultipartFormDataContent();
            using (var mem = new MemoryStream())
            {
                await stream.CopyToAsync(mem);
                var byteContent = new ByteArrayContent(mem.ToArray());
                multipartContent.Add(byteContent, "files", "my file");
                multipartContent.Add(new StringContent(p.FirstName), "FirstName");
                multipartContent.Add(new StringContent(p.LastName), "LastName");
                var response = await client.PostAsync(URI, multipartContent);
            }
        }
    }

然后，您可以在服务器端接收这些信息：

    [HttpPost]
    public async void Post([FromForm]Student student)
    {
        var form = Request.Form;
        var insideStudent = _dbContext.Students.FirstOrDefault(cus => cus.Id == student.Id);
        if (insideStudent != null)
        {
            insideStudent.FirstName = student.FirstName;
            insideStudent.LastName = student.LastName;
            _dbContext.SaveChanges();
        }
        else
        {
            var newStudent = new Student
            {
                FirstName = student.FirstName,
                LastName = student.LastName
            };
            if(form.Files.Any())
            {
                using (var stream = new MemoryStream())
                {
                    await form.Files[0].CopyToAsync(stream);
                    newStudent.Avatar = stream.ToArray();
                }
            }
            _dbContext.Students.Add(newStudent);
            _dbContext.SaveChanges();
        }
    }

---

谢谢你的回答。但是我得到了这个错误；请求失败，写入流的字节数超过了内容长度字节数大小specified@user1436795，你在哪里找到错误的？客户端还是服务器？客户端。代码未转到服务器。当调用client.PostAsync代码时。它可能是一个文件大小限制。尝试使用小文件。顺便说一句，你获取头像的代码流是什么样子的？公共静态流到流（图像图像，图像格式）{var stream=new System.IO.MemoryStream（）；Image.Save（流，格式）；stream.Position=0；return stream；}我用这种方式