使用POST多部分表单数据- Xamarin.forms

using System;
using System.Net.Http;
using System.Threading.Tasks;
using Xamarin.Forms;

public class FormDataUploader
{
    public async Task UploadFormData(string url, string filePath, string fieldName, string fieldValue)
    {
        using (var httpClient = new HttpClient())
        {
            using (var content = new MultipartFormDataContent())
            {
                // 添加文件
                var fileContent = new ByteArrayContent(await ReadFileAsByteArray(filePath));
                content.Add(fileContent, "file", "filename.jpg");

                // 添加字段
                content.Add(new StringContent(fieldValue), fieldName);

                // 发送请求
                var response = await httpClient.PostAsync(url, content);

                // 处理响应
                if (response.IsSuccessStatusCode)
                {
                    // 请求成功
                    var responseContent = await response.Content.ReadAsStringAsync();
                    Console.WriteLine("上传成功：" + responseContent);
                }
                else
                {
                    // 请求失败
                    Console.WriteLine("上传失败：" + response.StatusCode);
                }
            }
        }
    }

    private async Task<byte[]> ReadFileAsByteArray(string filePath)
    {
        // 读取文件内容并转换为字节数组
        return await DependencyService.Get<IFileService>().ReadFileAsByteArray(filePath);
    }
}