Для вашего запроса требуется заголовок "OCP-Apim-Subscription-Key". Взгляните на официальный пример:
using System;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
// Install Newtonsoft.Json with NuGet
using Newtonsoft.Json;
/// <summary>
/// The C# classes that represents the JSON returned by the Translator Text API.
/// </summary>
public class TranslationResult
{
public DetectedLanguage DetectedLanguage { get; set; }
public TextResult SourceText { get; set; }
public Translation[] Translations { get; set; }
}
public class DetectedLanguage
{
public string Language { get; set; }
public float Score { get; set; }
}
public class TextResult
{
public string Text { get; set; }
public string Script { get; set; }
}
public class Translation
{
public string Text { get; set; }
public TextResult Transliteration { get; set; }
public string To { get; set; }
public Alignment Alignment { get; set; }
public SentenceLength SentLen { get; set; }
}
public class Alignment
{
public string Proj { get; set; }
}
public class SentenceLength
{
public int[] SrcSentLen { get; set; }
public int[] TransSentLen { get; set; }
}
private const string key_var = "TRANSLATOR_TEXT_SUBSCRIPTION_KEY";
private static readonly string subscriptionKey = Environment.GetEnvironmentVariable(key_var);
private const string endpoint_var = "TRANSLATOR_TEXT_ENDPOINT";
private static readonly string endpoint = Environment.GetEnvironmentVariable(endpoint_var);
static Program()
{
if (null == subscriptionKey)
{
throw new Exception("Please set/export the environment variable: " + key_var);
}
if (null == endpoint)
{
throw new Exception("Please set/export the environment variable: " + endpoint_var);
}
using (var client = new HttpClient())
using (var request = new HttpRequestMessage())
{
// Build the request.
// Set the method to Post.
request.Method = HttpMethod.Post;
// Construct the URI and add headers.
request.RequestUri = new Uri(endpoint + route);
request.Content = new StringContent(requestBody, Encoding.UTF8, "application/json");
request.Headers.Add("Ocp-Apim-Subscription-Key", subscriptionKey);
// Send the request and get response.
HttpResponseMessage response = await client.SendAsync(request).ConfigureAwait(false);
// Read response as a string.
string result = await response.Content.ReadAsStringAsync();
// Deserialize the response using the classes created earlier.
TranslationResult[] deserializedOutput = JsonConvert.DeserializeObject<TranslationResult[]>(result);
// Iterate over the deserialized results.
foreach (TranslationResult o in deserializedOutput)
{
// Print the detected input language and confidence score.
Console.WriteLine("Detected input language: {0}\nConfidence score: {1}\n", o.DetectedLanguage.Language, o.DetectedLanguage.Score);
// Iterate over the results and print each translation.
foreach (Translation t in o.Translations)
{
Console.WriteLine("Translated to {0}: {1}", t.To, t.Text);
}
}
}
Console.Read();
}
https://docs.microsoft.com/en-us/azure/cognitive-services/translator/quickstart-translate?pivots=programming-language-csharp