ASP.NET Identity 2 UserManager get all users async

There is no way to do this asynchronously with the UserManager class directly. You can either wrap it in your own asynchronous method: (this might be a bit evil)

public async Task<IQueryable<User>> GetUsersAsync
{
    return await Task.Run(() =>
    {
        return userManager.Users(); 
    }
}

Or use the ToListAsync extension method:

public async Task<List<User>> GetUsersAsync()
{
    using (var context = new YourContext())
    {
        return await UserManager.Users.ToListAsync();
    }
}

Or use your context directly:

public async Task<List<User>> GetUsersAsync()
{
    using (var context = new YourContext())
    {
        return await context.Users.ToListAsync();
    }
}