EntityFramework中几种操作小结

目前项目中使用到的EntityFramework中几种操作小结，先标记下。没有详细介绍，后续有空的话再补充一些并完善一下。

列中加入RowVersion时间戳

    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; }

        [Timestamp]
        public Byte[] RowVersion { get; set; }
    }

 

查询中加入RowVersion比较

1. 编写扩展函数

    internal static class EntityFrameworkHelper
    {
        public static int Compare(this byte[] b1, byte[] b2)
        {
            throw new NotImplementedException("This is only for linq to sql");
        }
    }

1. 用扩展函数查询

    db.Products.Where(i => i.RowVersion.Compare(version) > 0).ToList();

 

乐观锁

    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; }

        [Timestamp, ConcurrencyCheck]
        public Byte[] RowVersion { get; set; }
    }

 

带过滤条件的DBSet

1. 添加Can a DbContext enforce a filter policy?一文中的FilteredDbSet，
2. 修改DbContext，使用FilteredDbSet替换默认的DbSet

    public IDbSet<Product> Products { get { return new FilteredDbSet<Product>(this, i=>i.IsRemoved == false); } }

 

标记删除

继承FilteredDbSet，重载其删除函数

    public interface IflagRemoveObject
    {
        bool IsRemoved { get; set; }
    }


    class FlagRemoveDbSet<T> : FilteredDbSet<T> where T : class, IflagRemoveObject
    {
        public override T Remove(T entity)
        {
            entity.IsRemoved = true;
            return entity;
        }
    }

 

单元测试：

1. 打桩DbSet：FakeDbSet
2. DbContext的封装