[API Proposal]: Adding a generic version of `FindByIdentity`

Start by locating Principal.FindByIdentity, the protected FindByIdentityWithType implementation, and the ComputerPrincipal, GroupPrincipal, and UserPrincipal declarations. Compare the proposed generic overloads with the existing API surface and determine the compatibility and validation requirements; done means the proposal is implemented consistently and the shown generic usage works.

Background and motivation

There is currently no way to use FindByIdentity in a generic way. There is a protected function FindByIdentityWithType, but this is not accessible from "outside".

We have functions that have to call FindByIdentity with different derived Principal classes. This currently causes us to call FindByIdentity as follows:

var result = typeof(T).GetMethod(nameof(Principal.FindByIdentity), [typeof(PrincipalContext), typeof(IdentityType), typeof(string)])?.Invoke(null, [adPrincipalContext, identityType, identityValue]) as T;

I think that due to the existence of FindByIdentityWithType, the implementation should also be straightforward and should not cause any problems.

API Proposal

namespace System.DirectoryServices.AccountManagement;

public abstract partial class Principal : System.IDisposable
{
    public static new T FindByIdentity<T>(PrincipalContext context, string identityValue) where T : Principal
    public static new T FindByIdentity<T>(PrincipalContext context, IdentityType identityType, string identityValue) where T : Principal
}

public partial class ComputerPrincipal : System.DirectoryServices.AccountManagement.AuthenticablePrincipal
{
    public static new T FindByIdentity<T>(PrincipalContext context, string identityValue) where T : ComputerPrincipal
    public static new T FindByIdentity<T>(PrincipalContext context, IdentityType identityType, string identityValue) where T : ComputerPrincipal
}

public partial class GroupPrincipal : System.DirectoryServices.AccountManagement.Principal
{
    public static new T FindByIdentity<T>(PrincipalContext context, string identityValue) where T : GroupPrincipal
    public static new T FindByIdentity<T>(PrincipalContext context, IdentityType identityType, string identityValue) where T : GroupPrincipal
}

public partial class UserPrincipal : System.DirectoryServices.AccountManagement.AuthenticablePrincipal
{
    public static new T FindByIdentity<T>(PrincipalContext context, string identityValue) where T : UserPrincipal
    public static new T FindByIdentity<T>(PrincipalContext context, IdentityType identityType, string identityValue) where T : UserPrincipal
}

API Usage

PrincipalContext ctx = new PrincipalContext(ContextType.Machine);
Principal.FindByIdentity<UserPrincipal>(ctx, IdentityType.SamAccountName, "Guest");

Alternative Designs

No response

Risks

No response