C# Http Request Wrapper (NOOB)

request.cs

        private async Task<HttpResponseMessage> Request(string url, HttpMethod method, Dictionary<string, string> headers, string body)
        {
            HttpClientHandler clientHandler = new HttpClientHandler();

            clientHandler.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
            clientHandler.Proxy = null;
            clientHandler.UseProxy = false;
            clientHandler.UseCookies = false;
            clientHandler.AllowAutoRedirect = false;

            using (HttpClient client = new HttpClient(clientHandler))
            {
                try
                {
                    foreach(var header in headers)
                    {
                        client.DefaultRequestHeaders.TryAddWithoutValidation(header.Key, header.Value);
                    }

                    if (method == HttpMethod.Get)
                    {
                        HttpResponseMessage res = await client.GetAsync(url);

                        return res;
                    } else if(method == HttpMethod.Post || method == HttpMethod.Put)
                    {
                        var parameters = new Dictionary<string, string>();
                        {
                        };

                        var parts = body.Split('&');
                        foreach(var part in parts)
                        {
                            var param = part.Split('=');
                            if (param.Length >= 2)
                            {
                                parameters.Add(param[0], param[1]);
                            }
                        }

                        var content = new FormUrlEncodedContent(parameters);

                        var request = new HttpRequestMessage(method, url);
                        request.Content = content;

                        HttpResponseMessage res = await client.SendAsync(request);

                        return res;
                    }

                } catch(Exception ex)
                {
                    MessageBox.Show(ex.ToString()); // デバッグ用
                    return null; // nullを代入し、この関数を呼び出した関数ルーチン (button_Click) で適切な戻り値かどうか判断できるようにする
                }
            }

            return null;
        }
        
        usage:
        
        private async void button1_Click(object sender, EventArgs e)
        {
            await Task.Factory.StartNew(async () =>
            {
                var headers = new Dictionary<string, string>();

                headers.Add("User-Agent", "Google BOT chan");
                headers.Add("HELLO", "BOYZ");

                var response = Request("http://localhost/test.php", HttpMethod.Get, headers, "").Result;
                var responseBody = await response.Content.ReadAsStringAsync();

                MessageBox.Show(responseBody);
            });
        }

localhost/test.php

<?php
var_dump(getallheaders());

[更新]
例外処理を追加、謝った実装を修正しました。

        private async Task<HttpResponseMessage> Request(string url, HttpMethod method, Dictionary<string, string> headers, string body)
        {
            HttpClientHandler clientHandler = new HttpClientHandler();

            clientHandler.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
            clientHandler.Proxy = null;
            clientHandler.UseProxy = false;
            clientHandler.UseCookies = false;
            clientHandler.AllowAutoRedirect = false;

            using (HttpClient client = new HttpClient(clientHandler))
            {
                try
                {
                    foreach(var header in headers)
                    {
                        client.DefaultRequestHeaders.TryAddWithoutValidation(header.Key, header.Value);
                    }

                    if (method == HttpMethod.Get)
                    {
                        HttpResponseMessage res = await client.GetAsync(url);

                        return res;
                    } else if(method == HttpMethod.Post || method == HttpMethod.Put)
                    {
                        var parameters = new Dictionary<string, string>();
                        {
                        };

                        var parts = body.Split('&');
                        foreach(var part in parts)
                        {
                            var param = part.Split('=');
                            if (param.Length >= 2)
                            {
                                parameters.Add(param[0], param[1]);
                            }
                        }

                        var content = new FormUrlEncodedContent(parameters);

                        var request = new HttpRequestMessage(method, url);
                        request.Content = content;

                        HttpResponseMessage res = await client.SendAsync(request);

                        return res;
                    }

                } catch(Exception ex)
                {
                    MessageBox.Show(ex.ToString()); // デバッグ用
                    return null; // nullを代入し、この関数を呼び出した関数ルーチン (button_Click) で適切な戻り値かどうか判断できるようにする
                }
            }

            return null;
        }