How to execute PowerShell script or cmdlets from C# code?

Program.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Linq;
using System.Management.Automation;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace PowerShellScriptExecutor
{
    class Program
    {
        static void Main(string[] args)
        {
            using (PowerShell PowerShellInst = PowerShell.Create())
            {
                string criteria = "system*";
                PowerShellInst.AddScript("Get-Service -DisplayName " + criteria);
                Collection<PSObject> PSOutput = PowerShellInst.Invoke();
                foreach (PSObject obj in PSOutput)
                {
                    if (obj != null)
                    {
                        Console.Write(obj.Properties["Status"].Value.ToString() + " - ");
                        Console.WriteLine(obj.Properties["DisplayName"].Value.ToString());
                    }
                }
                Console.WriteLine("Done");
                Console.Read();
            }           
        }
    }
}

Program1.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Linq;
using System.Management.Automation;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace PowerShellScriptExecutor
{
    class Program
    {
        static void Main(string[] args)
        {
            //Execute PS1(PowerShell script) file
            using (PowerShell PowerShellInst = PowerShell.Create())
            {
                string path = System.IO.Path.GetDirectoryName(@"C:\Temp\") + "\\Get-EventLog.ps1";
                if (!string.IsNullOrEmpty(path))
                    PowerShellInst.AddScript(System.IO.File.ReadAllText(path));

                Collection<PSObject> PSOutput = PowerShellInst.Invoke();
                foreach (PSObject obj in PSOutput)
                {
                    if (obj != null)
                    {
                        Console.Write(obj.Properties["EntryType"].Value.ToString() + " - ");
                        Console.Write(obj.Properties["Source"].Value.ToString() + " - ");
                        Console.WriteLine(obj.Properties["Message"].Value.ToString() + " - ");
                    }
                }
                Console.WriteLine("Done");
                Console.Read();
            }
        }
    }
}

Program2.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Linq;
using System.Management.Automation;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace PowerShellScriptExecutor
{
    class Program
    {
        static void Main(string[] args)
        {
            //execute powershell cmdlets or scripts using command arguments as process
            ProcessStartInfo processInfo = new ProcessStartInfo();
            processInfo.FileName = @"powershell.exe";
            //execute powershell script using script file
            //processInfo.Arguments = @"& {c:\temp\Get-EventLog.ps1}";
            //execute powershell command
            processInfo.Arguments = @"& {Get-EventLog -LogName Application -Newest 10 -EntryType Information | Select EntryType, Message}";
            processInfo.RedirectStandardError = true;
            processInfo.RedirectStandardOutput = true;
            processInfo.UseShellExecute = false;
            processInfo.CreateNoWindow = true;

            //start powershell process using process start info
            Process process = new Process();
            process.StartInfo = processInfo;
            process.Start();

            Console.WriteLine("Output - {0}", process.StandardOutput.ReadToEnd());
            Console.WriteLine("Errors - {0}", process.StandardError.ReadToEnd());
            Console.Read();
        }
    }
}