msgraph-dotnet-v5-rc-odata-cast

ODataCast.cs

//Fetching the members of a group who are of the type User
var usersInGroup = await graphServiceClient
    .Groups["group-id"]
    .Members
    .MicrosoftGraphUser
    .GetAsync();

List<User> userList = usersInGroup.Value;

//Similarly, members of the group of type ServicePrincipal 
var servicePrincipalsInGroup = await graphServiceClient
    .Groups["group-id"]
    .Members
    .MicrosoftGraphServicePrincipal
    .GetAsync();

List<ServicePrincipal> servicePrincipalList = servicePrincipalsInGroup.Value;