C# HttpWebRequest of type “application/x-www-form-urlencoded” - how to send '&' character in content body?

First install "Microsoft ASP.NET Web API Client" nuget package:

  PM > Install-Package Microsoft.AspNet.WebApi.Client

Then use the following function to post your data:

public static async Task<TResult> PostFormUrlEncoded<TResult>(string url, IEnumerable<KeyValuePair<string, string>> postData)
{
    using (var httpClient = new HttpClient())
    {
        using (var content = new FormUrlEncodedContent(postData))
        {
            content.Headers.Clear();
            content.Headers.Add("Content-Type", "application/x-www-form-urlencoded");

            HttpResponseMessage response = await httpClient.PostAsync(url, content);

            return await response.Content.ReadAsAsync<TResult>();
        }
    }
}

And this is how to use it:

TokenResponse tokenResponse = 
    await PostFormUrlEncoded<TokenResponse>(OAuth2Url, OAuth2PostData);

TokenResponse tokenResponse = 
    (Task.Run(async () 
        => await PostFormUrlEncoded<TokenResponse>(OAuth2Url, OAuth2PostData)))
        .Result

or (not recommended)

TokenResponse tokenResponse = 
    PostFormUrlEncoded<TokenResponse>(OAuth2Url, OAuth2PostData).Result;

可以参考的是FormUrlEncodedContent的使用，下面SendAsync是HttpClient的方法

  var data = new Dictionary<string, string>
            {
                {"on", $"{false}"},
                {TokenHelper.TokenName, TokenHelper.TokenValue}
            };
            var content = new FormUrlEncodedContent(data);
            var request = new HttpRequestMessage
            {
                Method = HttpMethod.Patch,
                RequestUri = new Uri($"{_setupFixture.Client.BaseAddress}SelfRegistration/Switch"),
                Content = content
            };
            //request.Headers.Add(TokenHelper.TokenName, TokenHelper.TokenValue);
            //request.Content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
            var response = await _setupFixture.Client.SendAsync(request);
            Assert.Equal(HttpStatusCode.OK, response.StatusCode);