c# - 我怎样才能让 EF 在保存时更新我的​​ ModifiedDate？

Question

我有以下用途:

using System;
using System.Data;
using System.Data.Entity;
using System.Data.Entity.ModelConfiguration.Conventions;

和下面的代码:

   public override int SaveChanges() 
    {
    foreach (var stateinfo in this.ChangeTracker.Entries(DataContext)
        .Where(e => e.Entity is StateInfo && (e.State == EntityState.Added || e.State ==  EntityState.Modified))
        .Select(e => e.Entity as StateInfo))
    ) {
        stateinfo.ModifiedDate = DateTime.Now;
       }
    return base.SaveChanges();
    }

但是这会出错，我不明白为什么。错误信息是说

Error 3 'System.Collections.Generic.IEnumerable' does not contain a definition for 'Where' and no extension method 'Where' accepting a first argument of type 'System.Collections.Generic.IEnumerable' could be found (are you missing a using directive or an assembly reference?)

Answer 1

请导入 System.Linq 命名空间