如何使用Get-Credential将光标保持在用户名上？

Add-Type -TypeDefinition @"
using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

public class SendKeysHelper
{
    [DllImport("user32.dll")]
    public static extern IntPtr GetForegroundWindow();

    [DllImport("user32.dll")]
    public static extern IntPtr GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);

    [DllImport("user32.dll")]
    public static extern bool AttachThreadInput(uint idAttach, uint idAttachTo, bool fAttach);

    [DllImport("kernel32.dll")]
    public static extern uint GetCurrentThreadId();

    public static void Send(string keys)
    {
        IntPtr foregroundWindow = GetForegroundWindow();
        uint currentThreadId = GetCurrentThreadId();
        uint windowThreadId;
        GetWindowThreadProcessId(foregroundWindow, out windowThreadId);
        AttachThreadInput(currentThreadId, windowThreadId, true);
        SendKeys.SendWait(keys);
        AttachThreadInput(currentThreadId, windowThreadId, false);
    }
}
"@

$credential = Get-Credential
[SendKeysHelper]::Send("{TAB}")

Add-Type -TypeDefinition @"
using System;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.Windows.Automation;

public class SetFocusHelper
{
    [DllImport("user32.dll")]
    public static extern IntPtr SetFocus(IntPtr hWnd);

    public static void SetFocusToUsernameField()
    {
        Process currentProcess = Process.GetCurrentProcess();
        AutomationElement currentElement = AutomationElement.FromHandle(currentProcess.MainWindowHandle);
        AutomationElement usernameField = currentElement.FindFirst(TreeScope.Descendants, new PropertyCondition(AutomationElement.AutomationIdProperty, "UsernameFieldAutomationId"));
        IntPtr usernameFieldHandle = new IntPtr(usernameField.Current.NativeWindowHandle);
        SetFocus(usernameFieldHandle);
    }
}
"@

$credential = Get-Credential
[SetFocusHelper]::SetFocusToUsernameField()