C# 保存历史表与具有依赖注入(inject)的 Entity Framework 的接口(interface)

Question

我们将 Net Core 2 与 Entity Framework 结合使用。我们的Sql数据库由很多表组成，Address, Account, Customer, Sales等。

有些表有对应的历史表:AddressHistory、CustomerHistory、

任何时候有人更改原始表中的某些内容，都应更新相应的历史表。 (不能使用 sql 时态表，因为我们有自定义历史逻辑)

我们正在尝试应用接口(interface)，我不太了解代码，有人可以提供一个快速的代码示例来说明如何使用接口(interface)实现它吗？尤其是SaveHistory部分，如何应用依赖注入(inject)？随意根据需要重写代码

public partial class TestDbContext
{

    public void AddEntityHistory<IEntityHistory>(IEntityHistory entity) where IEntityHistory: Address
    {  
       // do something 1 etc
    }

    public void AddEntityHistory<IEntityHistory>(IEntityHistory entity) where IEntityHistory: Customer
    {  
       // do something 2 etc
    }

    public override int SaveChanges()
    {
        SaveEntityHistory();
        return base.SaveChanges();
    }

    protected void SaveEntityHistory()
    {
         var modifiedEntities = ChangeTracker.Entries<IEntityHistory>().Where(e => e.State == EntityState.Added || e.State == EntityState.Modified);
         foreach(var entity in modifiedEntities)
         { 
              AddEntityHistory(entity);  // what is the code base here? giving error below, it should call appropriate AddEntityHistory Method for corresponding Entity
         }
    }
}

上面的错误:

Error CS0311 The type 'Interfaces.IEntityHistory' cannot be used as type parameter 'IEntityHistory' in the generic type or method 'PropertyContext.AddEntityHistory(IEntityHistory)'. There is no implicit reference conversion from 'Interfaces.IEntityHistory' to 'Data.Entities.Address'.

资源:

尝试利用类似的代码库:用于 CreateDate、UserId 等

https://dotnetcore.gaprogman.com/2017/01/26/entity-framework-core-shadow-properties/

Answer 1

方法的通用形式在这里根本不起作用。反射更适合你的要求:

public partial class TestDbContext
{

    public void AddEntityHistory(Address entity)
    {
        // do something 1 etc
    }

    public void AddEntityHistory(Customer entity)
    {
        // do something 2 etc
    }

    public override int SaveChanges()
    {
        SaveEntityHistory();
        return base.SaveChanges();
    }

    protected void SaveEntityHistory()
    {
        var modifiedEntities = ChangeTracker.Entries<IEntityHistory>()
            .Where(e => e.State == EntityState.Added || e.State == EntityState.Modified);
        foreach (var entity in modifiedEntities)
        {
            var methodInfo = this.GetType().GetMethod(nameof(AddEntityHistory), new[] { entity.Entity.GetType() });
            methodInfo.Invoke(this, new[] { entity.Entity });
        }
    }
}