Retrieve data from CRM using Azure clientId/clientSecret

using Microsoft.Xrm.Sdk;

using Microsoft.Xrm.Tooling.Connector;

using System;

using System.Configuration;

using Microsoft.Xrm.Sdk.Query;

using Microsoft.Xrm.Sdk.Organization;

using System.ServiceModel;

using System.Net;

using Microsoft.Crm.Sdk.Messages;

using System.Collections.Generic;

using System.Data;

using System.Runtime.InteropServices;

using System.Linq;

using Excel = Microsoft.Office.Interop.Excel;

using Microsoft.Xrm.Sdk.Messages;

using Microsoft.SharePoint;

using System.IO;

using Microsoft.IdentityModel.Clients.ActiveDirectory;

using System.Threading.Tasks;

using System.Net.Http;

using System.Text;

using System.Net.Http.Headers;

namespace CustomCode

{

    public class AzureRetrieveCall

    {

        public static void Main(string[] args)

        {

            //you will get some An unhandled exceptions of type 'System.AggregateException' occurred in mscorlib.dll

            //{ "An error occurred while sending the request."}

            //Hresult -2146233088

            //if you wont specify SecurityProtocol

            ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

            var contacts = CrmRequest(HttpMethod.Get, "https://ORGNAME.api.crm.dynamics.com/api/data/v9.1/contacts")

               .Result.Content.ReadAsStringAsync();

            // Similarly you can make POST, PATCH & DELETE requests  

        }

        public static async Task<HttpResponseMessage> CrmRequest(HttpMethod httpMethod, string requestUri, string body = null)

        {

            // Acquiring Access Token  

            var accessToken = await AccessTokenGenerator();

            var client = new HttpClient();

            var message = new HttpRequestMessage(httpMethod, requestUri);

            // OData related headers  

            message.Headers.Add("OData-MaxVersion", "4.0");

            message.Headers.Add("OData-Version", "4.0");

            message.Headers.Add("Prefer", "odata.include-annotations=\"*\"");

            // Passing AccessToken in Authentication header  

            message.Headers.Add("Authorization", $"Bearer {accessToken}");

            // Adding body content in HTTP request   

            if (body != null)

                message.Content = new StringContent(body, UnicodeEncoding.UTF8, "application/json");

            return await client.SendAsync(message);

        }

        public static async Task<string> AccessTokenGenerator()

        {

            string clientId = ""; // Your Azure AD Application ID  

            string clientSecret = ""; // Client secret generated in your App  

            string authority = "https://login.microsoftonline.com/APPTENANTID"; // Azure AD App Tenant ID  

            string resourceUrl = "https://ORGNAME.crm.dynamics.com"; // Your Dynamics 365 Organization URL  

            var credentials = new ClientCredential(clientId, clientSecret);

            var authContext = new Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext(authority);

            var result = await authContext.AcquireTokenAsync(resourceUrl, credentials);

            return result.AccessToken;

        }

    }

}