Добавьте файлы проекта.

zooManagerPro/ViewModels/LoginViewModel.cs

@@ -0,0 +1,36 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using zooManagerPro.Context;
+using zooManagerPro.Models;
+
+namespace zooManagerPro.ViewModels
+{
+    public partial class LoginViewModel : ObservableObject
+    {
+        [ObservableProperty]
+        public partial string Login { get; set; }
+        [ObservableProperty]
+        public partial string Password { get; set; }
+
+        [RelayCommand]
+        public async Task EntranceAsync()
+        {
+
+            await using ZooManagerProContext context = new();
+
+            if (context.Employees.FirstOrDefault(x => x.Login == Login && x.Password == Password) is Employee employee)
+            {
+                await MainView.Current.ReplaceAsync(new LoginView() // поменять
+                {
+                    DataContext = new LoginViewModel()
+                });
+            }
+           
+        }
+    }
+}

zooManagerPro/ViewModels/MainWindowViewModel.cs

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+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace zooManagerPro.ViewModels
+{
+    internal class MainWindowViewModel
+    {
+    }
+}

zooManagerPro/ViewModels/ViewModelBase.cs

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+using CommunityToolkit.Mvvm.ComponentModel;
+
+namespace zooManagerPro.ViewModels
+{
+    public abstract class ViewModelBase : ObservableObject
+    {
+    }
+}