builtin.cs

public class Rootobject
{
    public Languagedetection languageDetection { get; set; }
    public Keyphrases keyPhrases { get; set; }
    public Sentiment sentiment { get; set; }
}

public class Languagedetection
{
    public Document[] documents { get; set; }
    public object[] errors { get; set; }
}

public class Document
{
    public string id { get; set; }
    public Detectedlanguage[] detectedLanguages { get; set; }
}

public class Detectedlanguage
{
    public string name { get; set; }
    public string iso6391Name { get; set; }
    public float score { get; set; }
}

public class Keyphrases
{
    public Document1[] documents { get; set; }
    public object[] errors { get; set; }
}

public class Document1
{
    public string id { get; set; }
    public string[] keyPhrases { get; set; }
}

public class Sentiment
{
    public Document2[] documents { get; set; }
    public object[] errors { get; set; }
}

public class Document2
{
    public string id { get; set; }
    public float score { get; set; }
}