Please refer to the Introduction to PnP Core Component and OfficeDevPnP.Core for more details. I have created a console application and added SharePointPnPCore2016 NuGet package for the SharePoint 2016 version.
Code Snippet:
  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4. using System.Text;
  5. using System.Threading.Tasks;
  6. using Microsoft.SharePoint.Client;
  7. using OfficeDevPnP.Core;
  9. namespace SP2016PnPCoreComponentDemo
  10. {
  11. class Program
  12. {
  13. static void Main(string[] args)
  14. {
  15. // Input Parameters
  16. string siteUrl = "http://c7395723754/";
  17. string userName = "administrator";
  18. string password = "Mf165Nz2WV";
  19. string domain = "AD2012";
  20. string groupName = "Group created using PnP";
  21. string userLoginName = @"ad2012\administrator";
  23. OfficeDevPnP.Core.AuthenticationManager authMgr = new OfficeDevPnP.Core.AuthenticationManager();
  25. try
  26. {
  27. // Get the client context
  28. using (var ctx = authMgr.GetNetworkCredentialAuthenticatedContext(siteUrl, userName, password, domain))
  29. {
  30. // Check if user exists in the group
  31. if (ctx.Web.IsUserInGroup(groupName,userLoginName))
  32. {
  33. Console.WriteLine(userLoginName + " exists in the group: "+ groupName);
  34. Console.ReadLine();
  35. }
  36. }
  37. }
  39. catch (Exception ex)
  40. {
  41. Console.WriteLine("Error Message: " + ex.Message);
  42. }
  43. }
  44. }
  45. }