Get NetworkCredential from PSCredential splits Username into Username and Domain

During development of a PowerShell binary module I had to do deal with two different credential types (System.Management.Automation.PSCredential and System.Net.NetworkCredential) and came across a behaviour I wanted to write down.

The PowerShell binary module I developed contains several Cmdlets. One of them defines a parameter of type System.Management.Automation.PSCredential. Inside the Cmdlet we need to have an object of type System.Net.NetworkCredential. Getting such an object is easy as the System.Management.Automation.PSCredential provides an instance method called GetNetworkCredential(), which returns an object of type System.Net.NetworkCredential. This is the point I came across a behaviour I didn’t expect. I expected GetNetworkCredential() method to return a new NetworkCredential object with exactly the same the UserName and Password as the corresponding System.Management.Automation.PSCredential object. However in case the UserName property of the System.Management.Automation.PSCredential object contains a domain part the UserName property of the System.Net.NetworkCredential returned by GetNetworkCredential() does not contain the domain part anymore. The domain part gets cut and assigned to the Domain property of the System.Net.NetworkCredential as shown in the following code sample.

PS C:\>$usernameWithDomain = 'my-domain\arbitraryUser';
PS C:\>$password = 'P@ssw0rd';

PS C:\>$psCredential = [System.Management.Automation.PSCredential]::new($username, (ConvertTo-SecureString -AsPlainText -String $password -Force));
PS C:\>$psCredential.UserName;
my-domain\arbitraryUser

PS C:\>$networkCredentialFromPSCredential = $psCredential.GetNetworkCredential();
PS C:\>$networkCredentialFromPSCredential.UserName;
arbitraryUser
PS C:\>$networkCredentialFromPSCredential.Domain;
my-domain

The reason behind this behaviour is, that System.Net.NetworkCredential, in contrast to System.Management.Automation.PSCredential, has a Domain property, which will be filled up with the domain part of the UserName.