GET call of REST API that contains '/'-slash character in the value of a parameter

Let’s assume that we have the following scenario: I have a public HTTP endpoint and I need to post some content using GET command. One of the parameters contains special characters like “\” and “/”. If the endpoint is an ApiController than you may have problems if you encode the parameter using the http encoder.

using (var httpClient = new HttpClient())
            {
                httpClient.BaseAddress = baseUrl;
                Task<HttpResponseMessage> response = httpClient.GetAsync(string.Format("api/foo/{0}", "qwert/qwerqwer")));
                response.Wait();
                response.Result.EnsureSuccessStatusCode();
            }

One possible solution would be to encode the query parameter using UrlTokenEncode method of HttpServerUtility class and GetBytes method ofUTF8. In this way you would get the array of bytes of the parameter and encode them as a url token.
The following code show to you how you could write the encode and decode methods.

public class EncoderHelper
{
    public static string Encode(string content)
    {
        byte[] encodedBytes = UTF8Encoding.UTF8.GetBytes(content);
        string externalIdEncoded = HttpServerUtility.UrlTokenEncode(encodedBytes);

        return externalIdEncoded;
    }

    public static string Decode(string content)
    {
            var decodedBytes = HttpServerUtility.UrlTokenDecode(content);
        string externalId = UTF8Encoding.UTF8.GetString(decodedBytes);

        return externalId;
    }
}

There are also other ways to resolve this problem. This is just one of the possible solution to resolve this problem.
The call of the GET endpoint should look like something like this.

using (var httpClient = new HttpClient())
            {
                httpClient.BaseAddress = baseUrl;
                Task<HttpResponseMessage> response = httpClient.GetAsync(string.Format("api/foo/{0}", EncoderHelper.Encode("qwert/qwerqwer"))));
                response.Wait();
                response.Result.EnsureSuccessStatusCode();
            } 

Also, don't forget that you would need to use the Decode method on the other end.