Sample code for a google analytics console application.

GoogleAnaltyicsConsole.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using Google.Apis.AnalyticsReporting.v4;
using Google.Apis.AnalyticsReporting.v4.Data;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Services;
using Google.Apis.Util.Store;

namespace GoogleAnalyticsConsole
{
    // Instructions:
    //         1. Import nuget package: Google.Apis.AnalyticsReporting.v4
    //         2. Go to GoogleDeveloper console and create installed / native application credentials
    //         3. Download the json credential file.

    class Program
    {
        private const string PathToCredentialFile = "/home/development/creds/client.json";
        private const string GoogleAnalyticsViewId = "7811042";

        static void Main(string[] args)
        {
            // Initializes an Analytics Reporting API V4 service object.
            var service = Init();

            // Create the DateRange object.
            var dateRange = new DateRange
            {
                StartDate = "2015-06-15",
                EndDate = "2015-06-30"
            };

            // Create the Metrics object.
            var sessions = new Metric
            {
                Expression = "ga:sessions",
                Alias = "Sessions"
            };

            //Create the Dimensions object.
            var browser = new Dimension
            {
                Name = "ga:browser"
            };

            // Create the ReportRequest object.
            var reportRequest = new ReportRequest
            {
                ViewId = GoogleAnalyticsViewId,
                DateRanges = new List<DateRange> {dateRange},
                Dimensions = new List<Dimension> {browser},
                Metrics = new List<Metric> {sessions}
            };

            var requests = new List<ReportRequest> {reportRequest};

            // Create the GetReportsRequest object.
            var getReport = new GetReportsRequest {ReportRequests = requests};

            // Make the request.
            var response = service.Reports.BatchGet(getReport).Execute();


            // Print the results
            var report = response.Reports.FirstOrDefault();
            var header = report?.ColumnHeader;
            var dimensionHeaders = header.Dimensions;
            var metricHeaders = header.MetricHeader.MetricHeaderEntries;

            foreach (var reportRow in report.Data.Rows)
            {
                for (var i = 0; i < dimensionHeaders.Count && i < reportRow.Dimensions.Count; i++)
                {
                    Console.WriteLine($"{dimensionHeaders[i]}: {reportRow.Dimensions[i]}");
                }

                foreach (var t in reportRow.Metrics)
                {
                    var values = t.Values;
                    for (var k = 0; k < values.Count; k++)
                    {
                        var entry = metricHeaders[k];
                        Console.WriteLine($"{entry.Name}: {values[k]}");
                    }
                }
            }
        }


        private static AnalyticsReportingService Init()
        {
            var credentials = GetUserCredential(PathToCredentialFile, "user");
            return GetService(credentials);
        }

        /// <summary>
        /// This method get a valid service
        /// </summary>
        /// <param name="credential">Authecated user credentail</param>
        /// <returns>AnalyticsreportingService used to make requests against the Analyticsreporting API</returns>
        private static AnalyticsReportingService GetService(UserCredential credential)
        {
            try
            {
                if (credential == null)
                    throw new ArgumentNullException("credential");

                // Create Analyticsreporting API service.
                return new AnalyticsReportingService(new BaseClientService.Initializer()
                {
                    HttpClientInitializer = credential,
                    ApplicationName = System.Reflection.Assembly.GetExecutingAssembly().GetName().Name
                });
            }
            catch (Exception ex)
            {
                throw new Exception("Get AnalyticsReportingService service failed.", ex);
            }
        }


        /// <summary>
        /// ** Installed Aplication only ** 
        /// This method requests Authentcation from a user using Oauth2.  
        /// Credentials are stored in System.Environment.SpecialFolder.Personal
        /// Documentation https://developers.google.com/accounts/docs/OAuth2
        /// </summary>
        /// <param name="clientSecretJson">Path to the client secret json file from Google Developers console.</param>
        /// <param name="userName">Identifying string for the user who is being authentcated.</param>
        /// <param name="scopes">Array of Google scopes</param>
        /// <returns>authencated UserCredential</returns>
        private static UserCredential GetUserCredential(string clientSecretJson, string userName)
        {
            try
            {
                var scopes = new[]
                    {Google.Apis.AnalyticsReporting.v4.AnalyticsReportingService.Scope.AnalyticsReadonly};

                if (string.IsNullOrEmpty(clientSecretJson))
                    throw new ArgumentNullException("clientSecretJson");
                if (!File.Exists(clientSecretJson))
                    throw new Exception("clientSecretJson file does not exist.");

                // These are the scopes of permissions you need. It is best to request only what you need and not all of them               
                using var stream = new FileStream(clientSecretJson, FileMode.Open, FileAccess.Read);

                // sets the location the credentials will be stored.
                var credPath = Path.Combine(Directory.GetCurrentDirectory(), "credentials",
                    System.Reflection.Assembly.GetExecutingAssembly().GetName().Name);

                // Requesting Authentication or loading previously stored authentication for userName
                return GoogleWebAuthorizationBroker.AuthorizeAsync(GoogleClientSecrets.Load(stream).Secrets,
                    scopes,
                    userName,
                    CancellationToken.None,
                    new FileDataStore(credPath, true)).Result;
            }
            catch (Exception ex)
            {
                throw new Exception("Get user credentials failed.", ex);
            }
        }
    }
}

ServiceAccountExample.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Google.Apis.AnalyticsReporting.v4;
using Google.Apis.AnalyticsReporting.v4.Data;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Services;

namespace ConsoleApp1
{
    // Instructions:
    //         1. Import nuget package: Google.Apis.AnalyticsReporting.v4
    //         2. Go to GoogleDeveloper console and create service account credentials
    //         3. Download the json credential file.
    //         4. take the service account email address and add it as a user at the Account level of the Google Analytics account you wish to access.

    class Program
    {
        private const string PathToCredentialFile = "/home/linda/development/creds/serviceAccountCreds.json";

        private const string ServiceAccountEmail = "1046123799103-nk421gjc2v8mlr2qnmmqaak04ntb1dbp@developer.gserviceaccount.com";
        private const string GoogleAnalyticsViewId = "7811042";

        static void Main(string[] args)
        {
            // Initializes an Analytics Reporting API V4 service object.
            var service = Init();

            // Create the DateRange object.
            var dateRange = new DateRange
            {
                StartDate = "2015-06-15",
                EndDate = "2015-06-30"
            };

            // Create the Metrics object.
            var sessions = new Metric
            {
                Expression = "ga:sessions",
                Alias = "Sessions"
            };

            //Create the Dimensions object.
            var browser = new Dimension
            {
                Name = "ga:browser"
            };

            // Create the ReportRequest object.
            var reportRequest = new ReportRequest
            {
                ViewId = GoogleAnalyticsViewId,
                DateRanges = new List<DateRange> {dateRange},
                Dimensions = new List<Dimension> {browser},
                Metrics = new List<Metric> {sessions}
            };

            var requests = new List<ReportRequest> {reportRequest};

            // Create the GetReportsRequest object.
            var getReport = new GetReportsRequest {ReportRequests = requests};

            // Make the request.
            var response = service.Reports.BatchGet(getReport).Execute();


            // Print the results
            var report = response.Reports.FirstOrDefault();
            var header = report?.ColumnHeader;
            var dimensionHeaders = header.Dimensions;
            var metricHeaders = header.MetricHeader.MetricHeaderEntries;

            foreach (var reportRow in report.Data.Rows)
            {
                for (var i = 0; i < dimensionHeaders.Count && i < reportRow.Dimensions.Count; i++)
                {
                    Console.WriteLine($"{dimensionHeaders[i]}: {reportRow.Dimensions[i]}");
                }

                foreach (var t in reportRow.Metrics)
                {
                    var values = t.Values;
                    for (var k = 0; k < values.Count; k++)
                    {
                        var entry = metricHeaders[k];
                        Console.WriteLine($"{entry.Name}: {values[k]}");
                    }
                }
            }
        }


        private static AnalyticsReportingService Init()
        {
            var credentials = GetServiceAccountCredentials(ServiceAccountEmail, PathToCredentialFile);
            return GetService(credentials);
        }

        /// <summary>
        /// This method get a valid service
        /// </summary>
        /// <param name="credential">Authecated user credentail</param>
        /// <returns>AnalyticsreportingService used to make requests against the Analyticsreporting API</returns>
        private static AnalyticsReportingService GetService(GoogleCredential credential)
        {
            try
            {
                if (credential == null)
                    throw new ArgumentNullException(nameof(credential));

                // Create Analytics Reporting API service.
                return new AnalyticsReportingService(new BaseClientService.Initializer()
                {
                    HttpClientInitializer = credential,
                    ApplicationName = System.Reflection.Assembly.GetExecutingAssembly().GetName().Name
                });
            }
            catch (Exception ex)
            {
                throw new Exception("Get AnalyticsReportingService service failed.", ex);
            }
        }

        /// <summary>
        /// Authenticating to Google using a Service account
        /// Documentation: https://developers.google.com/accounts/docs/OAuth2#serviceaccount
        /// </summary>
        /// <param name="serviceAccountEmail">From Google Developer console https://console.developers.google.com</param>
        /// <param name="serviceAccountCredentialFilePath">Location of the .p12 or Json Service account key file downloaded from Google Developer console https://console.developers.google.com</param>
        /// <returns>AnalyticsService used to make requests against the Analytics API</returns>
        public static GoogleCredential GetServiceAccountCredentials(string serviceAccountEmail, string serviceAccountCredentialFilePath)
        {
            try
            {
                if (string.IsNullOrEmpty(serviceAccountCredentialFilePath))
                    throw new Exception("Path to the service account credentials file is required.");
                if (!File.Exists(serviceAccountCredentialFilePath))
                    throw new Exception("The service account credentials file does not exist at: " +
                                        serviceAccountCredentialFilePath);
                if (string.IsNullOrEmpty(serviceAccountEmail))
                    throw new Exception("ServiceAccountEmail is required.");
                
                var scopes = new[] {AnalyticsReportingService.Scope.AnalyticsReadonly};

                using var stream = new FileStream(serviceAccountCredentialFilePath, FileMode.Open, FileAccess.Read);
                return GoogleCredential.FromStream(stream) .CreateScoped(scopes);
            }
            catch (Exception ex)
            {
                throw new Exception("CreateServiceAccountAnalyticsReportingFailed", ex);
            }
        }
    }
}