.Net利用泛型封装EF CodeFirst 数据库初始值设定项

　　在使用 EF的code fist 方法我们可能会用到这三个类型对象DropCreateDatabaseAlways（总是删除创建对象） DropCreateDatabaseIfModelChanges（如果对象盖面删除创建对象） CreateDatabaseIfNotExists（如果对象不存在删除创建对象）

　　今天就利用泛型和工厂模式，将这三个对象封装以下，首先对三个对象类型分别创建子类，便于后期扩展。

    public class MyDropCreateDatabaseAlways<T> : DropCreateDatabaseAlways<T> where T : DbContext
    {

    }

    public class MyDropCreateDatabaseIfModelChanges<T> : DropCreateDatabaseIfModelChanges<T> where T : DbContext
    {

    }

    public class MyCreateDatabaseIfNotExists<T> : CreateDatabaseIfNotExists<T> where T : DbContext
    {


    }

在创建一个枚举类型方便调用

    public enum CreateDatabaseWayType
    {
        DropCreateDatabaseAlways = 1,
        DropCreateDatabaseIfModelChanges = 2,
        CreateDatabaseIfNotExists = 3,
    }

最后是一个工厂模式　

public static class CreateDatabaseFactory
    {
        public static IDatabaseInitializer<T> ChooseCreateDatabaseWay<T>(CreateDatabaseWayType createDatabaseWayType) where T : DbContext
        {
            switch (createDatabaseWayType)
            {
                case CreateDatabaseWayType.DropCreateDatabaseAlways:
                    return new MyDropCreateDatabaseAlways<T>();
                case CreateDatabaseWayType.DropCreateDatabaseIfModelChanges:
                    return new MyDropCreateDatabaseIfModelChanges<T>();
                case CreateDatabaseWayType.CreateDatabaseIfNotExists:
                default:
                    return new MyCreateDatabaseIfNotExists<T>();
            }
        }
    }

调用示例

在上下文的构造函数中

  public XHRTContext(bool init)
    : base("name=XHRT")
        {
            if (init)
            {
               SetInitializer(CreateDatabaseWay.ChooseCreateDatabasefactory<XHRTContext>(CreateDatabaseWayType.DropCreateDatabaseAlways));
                Database.Initialize(true);
            }
        }