Not Getting output from powershell script launched from c# code

I am trying to create an Excel AddIn, in which i need to run a powershell script inside my c# code.

The following ps script run well when launched in a console but i cannot get the output when launched in the code.

$user = 'user@domain';
$password = 'password';

$s_password = ConvertTo-SecureString $password -AsPlainText -Force;
$command = 'openfiles /query /s server /fo csv';

$p = New-Object System.Diagnostics.Process;
$p.StartInfo.FileName = 'powershell';
$p.StartInfo.UserName = $user;
$p.StartInfo.Password = $s_password;
$p.StartInfo.RedirectStandardError = $true;
$p.StartInfo.RedirectStandardOutput = $true;
$p.StartInfo.UseShellExecute = $false;
$p.StartInfo.Arguments = $command;

try{
    $p.Start();
    $stdout = $p.StandardOutput.ReadToEnd();
    $p.WaitForExit();
}
catch {}

$stdout

Here is my c# code so far :

try
{
    PowerShell ps = PowerShell.Create();
    ps.AddScript(@"script here");

    var results = ps.Invoke();
    MessageBox.Show(results.Count.ToString());

    if (results.Count > 0)
    {
        foreach (var psObject in results)
        {
            if(psObject != null) MessageBox.Show(psObject.BaseObject.ToString());
        }
    }
                    
    if (ps.Streams.Error.Count > 0)
    {
        Collection<ErrorRecord> errors = ps.Streams.Error.ReadAll();
        if (errors != null || errors.Count > 0)
        {
            foreach (ErrorRecord er in errors)
            {
                MessageBox.Show(er.Exception.ToString(), "Dévérouillage Fichier", MessageBoxButtons.OK, MessageBoxIcon.Error);
             }
        }
}
catch (Exception ex)
{
   MessageBox.Show(ex.Message, "Dévérouillage Fichier", MessageBoxButtons.OK, MessageBoxIcon.Error);
}

When i run this, it shows that there is 0 results.