如何在C#中设计并实现一个用于发送HTTP请求的封装类？

在C#中设计一个用于发送HTTP请求的封装类，通常会使用HttpClient类，这是一个高效且功能丰富的库，专门用于处理网络通信。以下是一个简单的封装示例：

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

public class HttpRequestClient
{
    private readonly HttpClient httpClient;

    public HttpRequestClient()
    {
        httpClient = new HttpClient();
    }

    // 发送GET请求
    public async Task<string> GetAsync(string url)
    {
        HttpResponseMessage response = await httpClient.GetAsync(url);
        response.EnsureSuccessStatusCode(); // 检查状态码是否成功
        return await response.Content.ReadAsStringAsync();
    }

    // 发送POST请求
    public async Task<string> PostAsync(string url, string requestBody)
    {
        using (var content = new StringContent(requestBody, Encoding.UTF8, "application/json"))
        {
            HttpResponseMessage response = await httpClient.PostAsync(url, content);
            response.EnsureSuccessStatusCode();
            return await response.Content.ReadAsStringAsync();
        }
    }

    // 示例：发送带文件的POST请求
    public async Task<string> UploadFilePostAsync(string url, string filePath)
    {
        MultipartFormDataContent formData = new MultipartFormDataContent();
        using (FileStream fileStream = File.OpenRead(filePath))
        {
            HttpContent fileContent = new StreamContent(fileStream);
            fileContent.Headers.ContentType = MediaTypeHeaderValue.Parse("application/octet-stream");
            formData.Add(fileContent, "file", Path.GetFileName(filePath));
        }
        HttpResponseMessage response = await httpClient.PostAsync(url, formData);
        response.EnsureSuccessStatusCode();
        return await response.Content.ReadAsStringAsync();
    }
}

// 使用示例
public static async Task Main()
{
    HttpRequestClient client = new HttpRequestClient();
    string result = await client.GetAsync("https://api.example.com/data");
    Console.WriteLine(result);
}