Running a complete powershell script from within C#

The below solution is quite different from the PowerShell snippet that you posted.

Overview: The Functionality is present in Class PinToTaskBar And Invoked from Class Program

Note: As mentioned in chat, it hasn't been tested

PS: I will attempt to convert your PS to C# when I get access to VS

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.IO;
using System.Management.Automation;
using System.Text;


    namespace ConfiguratorLibrary
    {
        public class PinToTaskBar
        {

            [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true, BestFitMapping = false, ThrowOnUnmappableChar = true)]
            internal static extern IntPtr LoadLibrary(string lpLibFileName);

            [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true, BestFitMapping = false, ThrowOnUnmappableChar = true)]
            internal static extern int LoadString(IntPtr hInstance, uint wID, StringBuilder lpBuffer, int nBufferMax);


            public static bool PinUnpinTaskbar(string filePath, bool pin)
            {
                if (!File.Exists(filePath)) throw new FileNotFoundException(filePath);
                int MAX_PATH = 255;
                var actionIndex = pin ? 5386 : 5387; // 5386 is the DLL index for"Pin to Tas&kbar", ref. win7dll.info/shell32_dll.html
                //uncomment the following line to pin to start instead
                //actionIndex = pin ? 51201 : 51394;
                StringBuilder szPinToStartLocalized = new StringBuilder(MAX_PATH);
                IntPtr hShell32 = LoadLibrary("Shell32.dll");
                LoadString(hShell32, (uint)actionIndex, szPinToStartLocalized, MAX_PATH);
                string localizedVerb = szPinToStartLocalized.ToString();

                string path = Path.GetDirectoryName(filePath);
                string fileName = Path.GetFileName(filePath);

                // create the shell application object
                dynamic shellApplication = Activator.CreateInstance(Type.GetTypeFromProgID("Shell.Application"));
                dynamic directory = shellApplication.NameSpace(path);
                dynamic link = directory.ParseName(fileName);

                dynamic verbs = link.Verbs();
                for (int i = 0; i < verbs.Count(); i++)
                {
                dynamic verb = verbs.Item(i);
                if (verb.Name.Equals(localizedVerb))
                {
                verb.DoIt();
                return true;
                }
                }
                return false;
            }

            static string originalImagePathName;
            static int unicodeSize = IntPtr.Size * 2;

            static void GetPointers(out IntPtr imageOffset, out IntPtr imageBuffer)
            {
                IntPtr pebBaseAddress = GetBasicInformation().PebBaseAddress;
                var processParameters = Marshal.ReadIntPtr(pebBaseAddress, 4 * IntPtr.Size);
                imageOffset = processParameters.Increment(4 * 4 + 5 * IntPtr.Size + unicodeSize + IntPtr.Size + unicodeSize);
                imageBuffer = Marshal.ReadIntPtr(imageOffset, IntPtr.Size);
            }

            internal static void ChangeImagePathName(string newFileName)
            {
            IntPtr imageOffset, imageBuffer;
            GetPointers(out imageOffset, out imageBuffer);

            //Read original data
            var imageLen = Marshal.ReadInt16(imageOffset);
            originalImagePathName = Marshal.PtrToStringUni(imageBuffer, imageLen / 2);

            var newImagePathName = Path.Combine(Path.GetDirectoryName(originalImagePathName), newFileName);
            if (newImagePathName.Length > originalImagePathName.Length) throw new Exception("new ImagePathName cannot be longer than the original one");

            //Write the string, char by char
            var ptr = imageBuffer;
            foreach(var unicodeChar in newImagePathName)
            {
            Marshal.WriteInt16(ptr, unicodeChar);
            ptr = ptr.Increment(2);
            }
            Marshal.WriteInt16(ptr, 0);

            //Write the new length
            Marshal.WriteInt16(imageOffset, (short) (newImagePathName.Length * 2));
            }

            internal static void RestoreImagePathName()
            {
            IntPtr imageOffset, ptr;
            GetPointers(out imageOffset, out ptr);

            foreach (var unicodeChar in originalImagePathName)
            {
            Marshal.WriteInt16(ptr, unicodeChar);
            ptr = ptr.Increment(2);
            }
            Marshal.WriteInt16(ptr, 0);
            Marshal.WriteInt16(imageOffset, (short)(originalImagePathName.Length * 2));
            }

            public static ProcessBasicInformation GetBasicInformation()
            {
            uint status;
            ProcessBasicInformation pbi;
            int retLen;
            var handle = System.Diagnostics.Process.GetCurrentProcess().Handle;
            if ((status = NtQueryInformationProcess(handle, 0,
            out pbi, Marshal.SizeOf(typeof(ProcessBasicInformation)), out retLen)) >= 0xc0000000)
            throw new Exception("Windows exception. status=" + status);
            return pbi;
            }

            [DllImport("ntdll.dll")]
            public static extern uint NtQueryInformationProcess(
            [In] IntPtr ProcessHandle,
            [In] int ProcessInformationClass,
            [Out] out ProcessBasicInformation ProcessInformation,
            [In] int ProcessInformationLength,
            [Out] [Optional] out int ReturnLength
            );

            public static IntPtr Increment(this IntPtr ptr, int value)
            {
            unchecked
            {
            if (IntPtr.Size == sizeof(Int32))
            return new IntPtr(ptr.ToInt32() + value);
            else
            return new IntPtr(ptr.ToInt64() + value);
            }
            }

            [StructLayout(LayoutKind.Sequential)]
            public struct ProcessBasicInformation
            {
                public uint ExitStatus;
                public IntPtr PebBaseAddress;
                public IntPtr AffinityMask;
                public int BasePriority;
                public IntPtr UniqueProcessId;
                public IntPtr InheritedFromUniqueProcessId;
            }


        }

        class TestClass
        {
            static void Main(string[] args)
            {
               var pin = new PinToTaskBar();
               try
                {

                    pin.ChangeImagePathName("explorer.exe");
                    pin.PinUnpinTaskbar(tempFilePath, true);
                }
                Catch(Exception ex)
                {
                    Console.WriteLine(ex.Message + ex.InnerException);
                }
                finally
                {
                    pin.RestoreImagePathName();
                }
            }
        }


    }

EDIT: I found reference to an article that explains functionality used

http://alexweinberger.com/main/pinning-network-program-taskbar-programmatically-windows-10/