使用单个LINQ查询使用Entity Framework删除多个记录

Question

我正在尝试使用LINQ执行DELETE,这将生成单个查询.

我是这样做的:

// NorthwintEntities is an ADO.NET Entitity Data Model
var northwindEntities = new NorthwindEntities();
northwindEntities.Order_Details.Delete(o => o.Order_ID == 11076);

这是我的扩展:

public static class EntityExtensions
{
    private static Regex rxTableName = new Regex(@"^FROM\s+(?<table>\[[^\]]*\](\.\[[^\]]*\]){0,2})\s+AS\s+(?<alias>\[[^\]]*\])", RegexOptions.Multiline);

    public static void Delete<T>(this ObjectSet<T> entity, Expression<Func<T, bool>> expression) where T : EntityObject
    {
        var selectQuery = entity.Where(expression).Select(x => 1);

        string selectQueryString = ((ObjectQuery)selectQuery).ToTraceString();

        string deleteQueryString = ConvertSqlSelectToDelete(selectQueryString);

        entity.Context.ExecuteStoreCommand(deleteQueryString);
    }

    private static string ConvertSqlSelectToDelete(string selectQuery)
    {
        if (selectQuery.IndexOf(" JOIN ") > -1)
        {
            throw new Exception("Query with JOIN is not supported: " + selectQuery);
        }

        Match match = rxTableName.Match(selectQuery);
        if (!match.Success)
        {
            throw new Exception("Unable to convert SELECT: " + selectQuery);
        }

        string deleteQuery = "DELETE \r\n" + selectQuery.Substring(match.Index);
        deleteQuery = deleteQuery.Replace(match.Groups["alias"].Value + ".", "");
        deleteQuery = deleteQuery.Replace("AS " + match.Groups["alias"].Value, "");

        return deleteQuery;
    }
}

这有效,但我有一些意见.

• 我不是在这里使用Regex的忠实粉丝,但这是我获得表名的唯一方法.(entity.EntitySet.Name并不总是返回正确的名称.[Order Details]是一个例子).
• 完成此操作后,我发现这个http://msmvps.com/blogs/matthieu/archive/2010/05/21/bulk-delete-v3.aspx 但无论如何都无法使其工作.保持从上下文中获取NotImplementedException为null.
• 使用连接删除似乎不起作用.我正在测试SQL Server Compact 3.5,也许这是一个限制.

所以我的问题是:有更简单的方法吗？如果是这样,它是什么？

任何帮助都将不胜感激.

Answer 1

1. 安装实体框架扩展库(PM> Install-Package EntityFramework.Extended)

2. 在代码中导入EntityFramework.Extensions

3. 删除内部查询指定的记录

   context.Orders.Where(o=>o.User_ID == 1).Delete();
   

删除用户ID = 1的订单内的所有记录

Answer 2

批量删除的一种方法是在外键上设置ON CASCADE DELETE.您需要在设计器中的关系上设置CASCADE,并在数据库中的关系上设置ON CASCADE DELETE.

要从订单EF中删除产品导航属性,将向产品数据库(产品属性数)+1语句执行操作.

我更喜欢这样做:

var order = context.Orders.Include(p=>p.Products).Where(o=>o.Order_ID == 11076);

foreach(Product product in order.Products.ToList())
{
  context.Entry(product).State = EntityState.Deleted;
}
context.Entry(order ).State = EntityState.Deleted;
context.SaveChanges();

希望能帮助到你.