Добавьте файлы проекта.

musicschoolapp/Pages/StudentEditingPage.xaml.cs

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+using Microsoft.Win32;
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Data.Entity;
+using System.Data.Entity.Infrastructure;
+using System.Data.Entity.Migrations;
+using System.Data.SqlClient;
+using System.Data.SqlTypes;
+using System.Linq;
+using System.Runtime.Remoting.Contexts;
+using System.Text;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Data;
+using System.Windows.Documents;
+using System.Windows.Input;
+using System.Windows.Media;
+using System.Windows.Media.Imaging;
+using System.Windows.Navigation;
+using System.Windows.Shapes;
+using System.IO;
+using System.Data.Entity.Validation;
+
+namespace musicschoolapp.Pages
+{
+    /// <summary>
+    /// Логика взаимодействия для StudentEditingPage.xaml
+    /// </summary>
+    public partial class StudentEditingPage : Page
+    {
+        musicschoolEntities1 mse = new musicschoolEntities1();
+        DbSet<Student> dbContext_;
+        List<Student> students1;
+        bool adding = false;
+        public StudentEditingPage()
+        {
+            InitializeComponent();
+            //dbContext_ = dbContext;
+            students1= mse.Student.ToList();
+            dGridStudent.ItemsSource = students1;
+        }
+
+
+        public int updateDB()
+        {
+            try
+            {
+                foreach (var student in students1)
+                {
+                    var original = mse.Student.Find(student.StudentID);
+
+                    if (original != null)
+                    {
+                        // Обновить запись в базе данных
+                        mse.Entry(original).CurrentValues.SetValues(student);
+                    }
+                    else
+                    {
+                        mse.Student.Add(student);
+                    }
+                }
+
+                int saveresult = mse.SaveChanges();
+                students1 = mse.Student.ToList();
+                dGridStudent.ItemsSource = students1;
+                return saveresult;
+            } catch(Exception ex) 
+            {
+                return -1;
+            }
+        }
+        private void dGridStudent_MouseDoubleClick(object sender, MouseButtonEventArgs e)
+        {
+            var grid = (DataGrid)sender;
+            if(grid.CurrentCell.Column != null)
+            { 
+            var cellInfo = grid.SelectedCells[grid.CurrentCell.Column.DisplayIndex];
+
+            if (cellInfo.Column.Header.ToString() == "Фото")
+            {
+                    if (MessageBox.Show("Вы дважды кликнули по столбцу 'Фото'. Изменить?", "Вопрос", MessageBoxButton.YesNo) == MessageBoxResult.Yes)
+                    {
+                        OpenFileDialog openFileDialog = new OpenFileDialog();
+                        openFileDialog.ShowDialog();
+                        if (mse.Student.Find((grid.SelectedItem as Student).StudentID) == null)
+                        {
+                            MessageBox.Show("Объект не создан.");
+                            grid.SelectedItem = -1;
+                            //return;
+                            mse.Student.Add(dGridStudent.SelectedItem as Student);
+                            try
+                            {
+                                mse.SaveChanges();
+                            }
+                            catch (DbEntityValidationException ex)
+                            {
+                                foreach (var entityValidationErrors in ex.EntityValidationErrors)
+                                {
+                                    foreach (var validationError in entityValidationErrors.ValidationErrors)
+                                    {
+                                        MessageBox.Show("Свойство: " + validationError.PropertyName + " Ошибка: " + validationError.ErrorMessage);
+                                    }
+                                }
+                            }
+
+                            MessageBox.Show("добавил");
+                            int index = grid.SelectedIndex;
+                            grid.SelectedIndex = -1;
+                            grid.SelectedIndex = index;
+                            dGridStudent_SelectionChanged(sender, new SelectionChangedEventArgs(DataGrid.SelectionChangedEvent, new Collection<object> { }, new Collection<object> { dGridStudent.SelectedItem }));
+                        }
+                        mse.Student.Find((grid.SelectedItem as Student).StudentID).photo = File.ReadAllBytes(openFileDialog.FileName);
+                        mse.SaveChanges();
+                        dGridStudent.ItemsSource = mse.Student.ToList();
+                    }
+                }
+            }
+            //}
+        }
+        private void dGridStudent_SelectionChanged(object sender, SelectionChangedEventArgs e)
+        {
+            if (e.AddedItems != null && e.AddedItems.Count > 0)
+            {
+            
+
+            }
+            else if (e.RemovedItems != null && e.RemovedItems.Count > 0)
+            {
+
+                Student selectedStudent = (e.RemovedItems[0] as Student);
+                if (selectedStudent != null)
+                {
+                    Student studentInDb = mse.Student.Find(selectedStudent.StudentID);
+                    if (studentInDb != null)
+                    {
+                        mse.Student.Remove(studentInDb);
+                        
+                        try
+                        {
+                            mse.SaveChanges();
+                        }
+                        catch (DbUpdateException ex)
+                        {
+                            
+                            MessageBox.Show("Запись, похоже, удалить нельзя.\n\n" + ex.InnerException);
+                            students1 = mse.Student.ToList();
+                            mse.Entry(studentInDb).State = System.Data.EntityState.Unchanged;
+
+
+                            return;
+                        }
+                        students1.Remove(dGridStudent.SelectedItem as Student);
+                        dGridStudent.SelectedIndex = -1;
+                        MessageBox.Show("Удалено");
+                    }
+                }
+            }
+
+        }
+
+        private void BtnEdit_Click(object sender, RoutedEventArgs e)
+        {
+            {
+                
+            
+            }
+        }
+    }
+}