C#

//assigned Application Id
private const string appId = "4C782603-8B36-485A-AE33-557CF6392E44";

//authentication token - should be saved for up to an hour.
private static dynamic authToken = null;    
     
//api base url
private const string apiBaseUrl = "https://openapitest.intelichart.com/";    
    
//api relative urls
private const string vitalSignsUrl = "api/clinical/vitalsign/get";
        
static void Main(string[] args)
{
    try
    {
        GetToken(); //note - this should be stored for up to an hour.
        if (authToken == null)
        {
            Console.WriteLine("Could not get token");
            return;
        } 

        var json = @"
        {
            'personuid': '048114058233091195065092183127160152030014254207',
            'startdate': '08/24/2015',
            'enddate':   '08/25/2015'
        }";

        try
        {
            var endResponse = Post(apiBaseUrl, json);
            /* do something with response*/
            /* check for null*/        
        }
        catch (Exception ex1)
        {
            Console.WriteLine(ex.Message);
            //handle error
        }
                
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }

}

private static dynamic Post(string url, string payload)
{
    dynamic ret = null;

    //convert to json object
    var model = JsonConvert.DeserializeObject<dynamic>(payload) as object;

    using (var client = new HttpClient(GetHttpClientHandler()))
    {
        //set the base address for api calls. This is based on environment you are calling
        client.BaseAddress = new Uri(url);
        client.DefaultRequestHeaders.Accept.Clear();

        //set content type to json
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

        //this token gottent from GetToken() function earlier
        //add authentication to header
        client.DefaultRequestHeaders.Authorization = 
            new AuthenticationHeaderValue(authToken.TokenType, authToken.Token.ToString());

        //add clientId to header
        client.DefaultRequestHeaders.Add("ApplicationId", appId);

        //get response from server
        using (var response = client.PostAsJsonAsync(vitalSignsUrl, model).Result)
        {
            var responseText = response.Content.ReadAsStringAsync().Result;

            if (response.StatusCode != HttpStatusCode.OK) //error happened
            {
                Console.WriteLine(responseText);
            }
            else
            {
                //convert to json object
                ret = JsonConvert.DeserializeObject<dynamic>(responseText); 

                //print out json in readable format
                Console.WriteLine(JsonConvert.SerializeObject(ret, Formatting.Indented)); 
            }
        }
    }

    return ret;
}
                                                                          
private static HttpClientHandler GetHttpClientHandler()
{
    var handler = new HttpClientHandler
    {
        UseCookies = false,
        UseProxy = true,
        UseDefaultCredentials = false
    };
    return handler;
}