MYSQLEntityFrameworkMVVMSaveChanges()withObservableCollection

1. 将MYSQL数据库和Entity Framework集成到MVVM框架中。
2. 创建一个包含ObservableCollection属性的实体类。
3. 使用Entity Framework将实体类映射到MYSQL数据库中的数据表。
4. 实现保存更改的逻辑，使用SaveChanges()方法将更改应用到数据库中。 以下是一些示例代码：

实体类：

public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Address { get; set; }
    public ObservableCollection<Order> Orders { get; set; }
}

使用Entity Framework将实体类映射到MYSQL数据库的数据表：

public class MyDbContext : DbContext
{
    public DbSet<Customer> Customers { get; set; }
    public DbSet<Order> Orders { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseMySQL("server=localhost;database=mydatabase;user=root;password=mypassword");
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Customer>()
            .HasMany(c => c.Orders)
            .WithOne(o => o.Customer)
            .HasForeignKey(o => o.CustomerId);
    }
}

保存更改的逻辑：

public class CustomerViewModel : INotifyPropertyChanged
{
    private MyDbContext _dbContext;
    private ObservableCollection<Customer> _customers;
    public event PropertyChangedEventHandler PropertyChanged;

    public ObservableCollection<Customer> Customers
    {
        get { return _customers; }
        set
        {
            _customers = value;
            OnPropertyChanged("Customers");
        }
    }

    public CustomerViewModel()
    {
        _dbContext = new MyDbContext();
        Customers = new ObservableCollection<Customer>(_dbContext.Customers.Include(c => c.Orders).ToList());
    }

    public void SaveChanges()
    {
        _dbContext.SaveChanges();
    }

    protected void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}