SharePoint C# PowerShell Script not executing correctly

Question

So I have a script to migrate users and I want to use that script in my application to make things faster and more simple. But there is some kind of problem, that I can't crack with current code.

Code runs to error in RunScript when I start Invoking pipeline.

Note Script itself works without a problem, when I run it in PowerShell ISE as administrator

Here is my code

public class Migration
{
    private static string scriptEmail = @"Add-PSSnapin Microsoft.SharePoint.Powershell
            $url = '{0}'
            $oldIdentity = '{1}'
            $newIdentity = '{2}'
            $email = '{3}'

            $user = Get-SPUser -web $url -Identity $oldIdentity
            Move-SPUser -IgnoreSID -Identity $user -NewAlias $newIdentity
            $newUser=Get-SPUser -Identity '$newIdentity' -Web $url
            Set-SPUser -Identity $newUser -Email $email
        ";

    private static string scriptNoEmail = @"Add-PSSnapin Microsoft.SharePoint.Powershell
            $url = '{0}'
            $oldIdentity = '{1}'
            $newIdentity = '{2}'

            $user = Get-SPUser -web $url -Identity $oldIdentity
            Move-SPUser -IgnoreSID -Identity $user -NewAlias $newIdentity
            $newUser=Get-SPUser -Identity '$newIdentity' -Web $url
        ";

    /// <summary>
    /// Starts user migration proccess
    /// </summary>
    /// <param name="users">Users to migrate in order (first will be main user)</param>
    /// <param name="email">User end email</param>
    /// <param name="url">Site URL</param>
    /// <returns>Did code excecute without errors</returns>
    public static bool Start(List<WorkUser> users, string email, string url)
    {
        try
        {
            for (int i = users.Count; i > 1; i--)
            {
                string script = string.Empty;
                if (email != string.Empty) // Kui on antud email ette (lisab etteantud emaili kasutajale)
                {
                    script = string.Format(scriptEmail, url, users[i - 1].Account, users[i - 2].Account, email);
                }
                else // Kui emaili pole ette antud (kasutaja andmed jäävad samaks)
                {
                    script = string.Format(scriptNoEmail, url, users[i - 1].Account, users[i - 2].Account);
                }
                Log.WriteToLog(string.Format("Running script | {0} |", script));
                RunScript(script);
                Log.WriteToLog(string.Format("Account \"{0}\" migrated to \"{1}\"", users[i - 1].Account, users[i - 2].Account));
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.ToString());
            Log.WriteToLog(ex.ToString());
            return false;
        }
        return true;
        //string res = RunScript(script);
    }

    /// <summary>
    /// Runs and excecutes PowerShell script
    /// </summary>
    /// <param name="scriptText">PowerShell script to excecute</param>
    /// <returns>Result</returns>
    private static string RunScript(string scriptText)
    {
        // create Powershell runspace 
        using (Runspace runspace = RunspaceFactory.CreateRunspace())
        {
            // open it 
            runspace.Open();

            RunspaceInvoke scriptInvoker = new RunspaceInvoke(runspace);
            scriptInvoker.Invoke("Set-ExecutionPolicy Unrestricted");

            // create a pipeline and feed it the script text 
            Pipeline pipeline = runspace.CreatePipeline();
            pipeline.Commands.AddScript(scriptText);

            // add an extra command to transform the script output objects into nicely formatted strings 
            // remove this line to get the actual objects that the script returns. For example, the script 
            // "Get-Process" returns a collection of System.Diagnostics.Process instances. 
            pipeline.Commands.Add("Out-String");

            // execute the script 
            Collection<PSObject> results = pipeline.Invoke();

            // close the runspace 
            runspace.Close();

            // convert the script result into a single string 
            StringBuilder stringBuilder = new StringBuilder();
            foreach (PSObject obj in results)
            {
                stringBuilder.AppendLine(obj.ToString());
            }

            // return the results of the script that has 
            // now been converted to text 
            return stringBuilder.ToString();
        }
    }
}

Error, that I am getting is following:

    System.Management.Automation.ParameterBindingValidationException: Cannot validate argument on parameter 'Identity'. The argument is null. Provide a valid value for the argument, and then try running the command again. ---> System.Management.Automation.ValidationMetadataException: The argument is null. Provide a valid value for the argument, and then try running the command again.
   at System.Management.Automation.ValidateNotNullAttribute.Validate(Object arguments, EngineIntrinsics engineIntrinsics)
   at System.Management.Automation.ParameterBinderBase.BindParameter(CommandParameterInternal parameter, CompiledCommandParameter parameterMetadata, ParameterBindingFlags flags)
   --- End of inner exception stack trace ---
   at System.Management.Automation.Runspaces.PipelineBase.Invoke(IEnumerable input)
   at UserMigrationTool.Code.Migration.RunScript(String scriptText) in c:\TauriVS\BCS.Sharepoint.Products.2013\UserMigrationTool\Code\Migration.cs:line 98
   at UserMigrationTool.Code.Migration.Start(List`1 users, String email, String url) in c:\TauriVS\BCS.Sharepoint.Products.2013\UserMigrationTool\Code\Migration.cs:line 63

Answer 1

Make sure that the assigned value of Identity parameter is matched "DomainName\Username" at all similar statements use that like

Get-SPUser -web $url -Identity $oldIdentity

Also, it's preferred to assign parameter like this

pipeline.Parameters.Add("Identity", oldIdentity);