вывод работает

WorkWithDatabase/ViewModels/MainPageVM.cs

@@ -23,7 +23,7 @@ namespace WorkWithDatabase.ViewModels
             MainWindowViewModel.Instance.PageContent = new PageAddTeacher();
         }
 
-        public void ToPageEditTeacher()
+        public void ToPageEditTeacher(int IdT)
         {
             MainWindowViewModel.Instance.PageContent = new PageEditTeacher();
         }

WorkWithDatabase/ViewModels/PageAddTeacherVM.cs

@@ -1,4 +1,5 @@
-using System;
+using ReactiveUI;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -9,6 +10,17 @@ namespace WorkWithDatabase.ViewModels
 {
     internal class PageAddTeacherVM: ViewModelBase
     {
+        /*Teacher? _newTeaher;
 
+        public Teacher? NewTeaher { get => _newTeaher; set => this.RaiseAndSetIfChanged(ref _newTeaher,value); }
+
+        public PageAddTeacherVM()
+        {
+            _newTeaher = new Teacher();
+        }
+        public PageAddTeacherVM(int IdT)
+        {
+            _newTeaher = new Teacher();
+        }*/
     }
 }