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Powershell in C# Get-Credential UI

I'm writing an installer wrapper for a Windows C# Service. The installer is written in C# but needs to execute Powershell commands. As part of the installation I need to either get the current user's credentials, or have the user provide credentials. I need to use a PowerShell for the service installation (using New-Service), but I need to provide the credentials as a PSCredential object.
Such an object can be returned by Get-Credentials, but I can't invoke this command without accessing the PS Host UI, which I don't seem to be able to do.
I can do this the lazy way, and throw up a custom dialog asking for a username and password, and cram those in to a new PSCredential, but that is very bad practice.
I can also get these credentials by PInvoking my way through CredUIPromptForWindowsCredentials, but again, this is extremely kludgy and eventually results in a plain text password in memory which I'd like to avoid.
Surely there is some intermediate? I'm running this interaction from a WPF form, so I can happily present the user with a credentials dialog, but I don't know how to do this in a sensible way.
It would also be nice if there was a secure way to create a service and pass through the currently logged in user as the "run as" user.
Simply put, I want to create a Windows service that runs as a specified user. How do I do this programmatically in C#?
Any advice would be appreciated.

It is a bit unclear of what you want to do.
Are you using powershell inside c# code or powershell only, to install the c# code?
Are you searching for a solution in powershell or c#?
Are you asking for a solution on password security or on secure service creation?
This (https://learn.microsoft.com/en-us/dotnet/api/system.security.securestring?view=net-7.0) c# class: "Represents text that should be kept confidential, such as by deleting it from computer memory when no longer needed. This class cannot be inherited."
I would use this (https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.security/convertto-securestring?view=powershell-7.3) for powershell.

How to write a windows program that replaces password authentication on logon screen

I'm looking for a way to replace the windows text password login.
My app should be launched automatically and ask the user a few questions, if everything is correct than the user should be allowed to be logged in.
I don't my that a text password will be submitted by my app in the background.
the environment is very similar to face recognition/finger print recognition login.
Where should i start? (:
Thanks

See here:
Windows Credential Provider with C#
and here: http://pgina.org/
(I have no personal experience with this ... as yet.)

This is possible.
Different Windows versions offer different mechanisms to achieve what you want:
in Vista and newer you have to create a Credential Provider
in XP you need to create and a GINA DLL
BEWARE: it might be difficult to do this in .NET, you most probably will need to code a native solution (C/C++ for example).

windows authentication in win 8 apps

I am developing a windows 8 app using c# and xaml. My app should be able to implement windows authentication so that it can allow the logged in user to launch the app. Can anyone help or give me a code snippet to solve this problem???
thanks in advance

To Enable Windows Authentication in windows 8 App
Go to Package.appxmanifest file.
Go to Capabilities tab. Check the Enterprise Authentication feature on the Page.
Include the Namespace
using Windows.System.UserProfile;
Eg to Use the Profile User Name :
txtUserName.Text = await UserInformation.GetFirstNameAsync();
This is how you will get the details of the Windows Authentication user.
Hope this helped you !

You can't do that. Windows 8 "Immersive" applications are sandboxed and have no access to Windows' own user management. In any event user passwords are hashed (a one-way transform), you can't read back the original passwords even if you had access to the SAM file.
If you want a user's Windows password you'll have to ask them up-front, but I gurantee no (intelligent) user would voluntarily agree to this, and chances are your application would be denied on the Windows app-store if you did submit it.

How to show the user the default windows authentication prompt from a windows form using c#?

I thought this would be a very common practice, but I am having a hard time finding anything on how to show the user a default windows authentication credential prompt in c#?
Users will be using this windows forms app to connect to a web service on a different domain, so I cant just pass in the default credentials. These users will have a separate login to access the web service, and I want them to be prompted by the default Windows prompt, and then I can pass their creds through to the web service.
Thanks!

This was answered on SO a while back, I believe. You can use the credential management API. Here's a link with a code example that should get you started.

You need to P/invoke CredUIPromptForWindowsCredentials on Vista and up, or CredUIPromptForCredentials on XP.

C# Validate an Administrator from Login information

I'm having a bit of a problem with an application I am writing in C#. I can't seem to find a way to check if a user is an administrator just from their username and password. I haven't seen anything helpful for doing this elsewhere and all tries to attempting such with WindowsIdentity end up helpless. I am aware of UAC programming with Windows Vista and Windows 7, however I plan on supporting Windows XP; thus rendering the possibility of using administrator access via UAC unlikely. I am only looking for a way of creating a method that takes the string Username and string Password and returns the boolean of if the credentials refer to an administrator account.
Is there any feasible way of doing this?
Thanks.

Here's an SO question that might help you out.
Also, the MSDN entry for WindowsImpersonationContext has a good example.