操作Mysql数据库

- Microsoft.EntityFrameworkCore.Tools
- Microsoft.EntityFrameworkCore.Design
- Microsoft.EntityFrameworkCore.Sqlite

>d Add-Migration Init
update-database

```java
public class Employee
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public float Salary { get; set; }
}
```

```java
public class EmployeeConfig : IEntityTypeConfiguration<Employee>
{
    public void Configure(EntityTypeBuilder<Employee> builder)
    {
        builder.ToTable("T_Employee"); //ToTable这个扩展方法来自Microsoft.EntityFrameworkCore.Tools
        builder.Property(x => x.Name).IsRequired().HasMaxLength(20);  //配置是否为空和最大长度

}
}
```

```java
public class MyDbContext : DbContext
{
    public DbSet<Employee> Employees { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
     string MySqlConneStr = "server=101.42.52.242;user=root;password=root19890103_spp;database=EFTest";
        //特别注意:此处使用的是:Pomelo.EntityFramework.MySql包.
        var serverVersion = new MySqlServerVersion(new Version(8, 0, 34));
        optionsBuilder.UseMySql(MySqlConneStr, serverVersion);
    }

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        modelBuilder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);
    }
}
```

```java
using MyDbContext ctx = new MyDbContext();
Employee employee = new Employee { Age = 18, Name = "张三", Salary = 5000 };
ctx.Add(employee);
ctx.SaveChanges();
```