将C#参数传递到Powershell脚本-无法验证参数'；上的参数；身份'；

我正在尝试用C#编写一个Windows窗体应用程序，为指定用户输出AD属性。我希望它的工作方式是，用户在文本框中输入一个值（用户名），该值作为参数传递给Powershell脚本，输出显示在表单中

我用于创建参数和调用脚本的C#代码如下：

private string RunScript(string scriptText)
    {
        // create Powershell runspace 
        Runspace runspace = RunspaceFactory.CreateRunspace();
        // open it 
        runspace.Open();
        RunspaceInvoke scriptInvoker = new RunspaceInvoke(runspace);
        // create a pipeline and feed it the script text 
        Pipeline pipeline = runspace.CreatePipeline();
        pipeline.Commands.AddScript(scriptText);
        pipeline.Commands.Add(new Command("Set-ExecutionPolicy Unrestricted -Scope Process", true));
        // "Get-Process" returns a collection of System.Diagnostics.Process instances. 
        pipeline.Commands.Add("Out-String");
        //Create parameter and pass value to script
        String username = textBox3.Text;
        String scriptfile = @"c:''scripts''getpasswordexpirydate.ps1";
        Command myCommand = new Command(scriptfile, false);
        CommandParameter testParam = new CommandParameter("username", username);
        myCommand.Parameters.Add(testParam);
        pipeline.Commands.Add(myCommand);
        // 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();
    }

我的PowerShell脚本如下：

param([string]$username)
function Get-XADUserPasswordExpirationDate() {
Param ([Parameter(Mandatory=$true,  Position=0,  ValueFromPipeline=$true, HelpMessage="Identity of the Account")]
[Object] $accountIdentity)
PROCESS {
    $accountObj = Get-ADUser $accountIdentity -properties PasswordExpired, PasswordNeverExpires, PasswordLastSet
    if ($accountObj.PasswordExpired) {
        echo ("Password of account: " + $accountObj.Name + " already expired!")
    } else { 
        if ($accountObj.PasswordNeverExpires) {
            echo ("Password of account: " + $accountObj.Name + " is set to never expires!")
        } else {
            $passwordSetDate = $accountObj.PasswordLastSet
            if ($passwordSetDate -eq $null) {
                echo ("Password of account: " + $accountObj.Name + " has never been set!")
            }  else {
                $maxPasswordAgeTimeSpan = $null
                $dfl = (get-addomain).DomainMode
                if ($dfl -ge 3) { 
                    ## Greater than Windows2008 domain functional level
                    $accountFGPP = Get-ADUserResultantPasswordPolicy $accountObj
                    if ($accountFGPP -ne $null) {
                        $maxPasswordAgeTimeSpan = $accountFGPP.MaxPasswordAge
                    } else {
                        $maxPasswordAgeTimeSpan = (Get-ADDefaultDomainPasswordPolicy).MaxPasswordAge
                    }
                } else {
                    $maxPasswordAgeTimeSpan = (Get-ADDefaultDomainPasswordPolicy).MaxPasswordAge
                }
                if ($maxPasswordAgeTimeSpan -eq $null -or $maxPasswordAgeTimeSpan.TotalMilliseconds -eq 0) {
                    echo ("MaxPasswordAge is not set for the domain or is set to zero!")
                } else {
                    echo ("Password of account: " + $accountObj.Name + " expires on: " + ($passwordSetDate + $maxPasswordAgeTimeSpan))
                }
            }
        }
    }
}
}
Get-XADUserPasswordExpirationDate $username
Get-ADUser $username -Properties * | Select-Object DisplayName,LockedOut,LastLogonDate,kPMG-User-GOAccountType,kPMG-User-GOCompanyGroup,kPMG-User-GOFunction,kPMG-User-GOGrade,kPMG-User-GOManagementLevel,kPMG-User-GOMemberFirmGroup,kPMG-User-GPID,kPMG-User-GOMailDisclaimer,kPMG-User-GOMailSync

如果我在PowerShell中运行脚本，例如.''script.ps1 jsmith，并将"jsmith"作为参数，则它可以工作，但当使用C#参数时，它不接受该参数，并且每次都会抛出"无法验证参数"Identity"上的参数"错误。

我的C#代码中有没有做错什么，导致这个参数不能传递到脚本并接受它作为输入？

感谢