Check out example codes for "console application in c# ms crm". It will help you in understanding the concepts better.

Code Example 1

IOrganizationService organizationService = null;

try
 {
 ClientCredentials clientCredentials = new ClientCredentials();
 clientCredentials.UserName.UserName = "<ProvideUserName>@<ProvideYourOrgName>.onmicrosoft.com";
 clientCredentials.UserName.Password = "<ProvideYourPassword>";

// For Dynamics 365 Customer Engagement V9.X, set Security Protocol as TLS12
 ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
// Get the URL from CRM, Navigate to Settings -> Customizations -> Developer Resources
// Copy and Paste Organization Service Endpoint Address URL
organizationService = (IOrganizationService)new OrganizationServiceProxy(new Uri("https://<ProvideYourOrgName>.api.<CRMRegion>.dynamics.com/XRMServices/2011/Organization.svc"),
 null, clientCredentials, null);

if (organizationService != null)
 {
 Guid userid = ((WhoAmIResponse)organizationService.Execute(new WhoAmIRequest())).UserId;

if (userid != Guid.Empty)
 {
 Console.WriteLine("Connection Established Successfully...");
 }
 }
 else
 {
 Console.WriteLine("Failed to Established Connection!!!");
 }
 }
 catch (Exception ex)
 {
 Console.WriteLine("Exception caught - " + ex.Message); 
 }
 Console.ReadKey();

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