如何将linq中的计算列映射到sql类 [英] how to map a computed column in linq to sql classes

问题描述

如何将计算列映射到我的LinqToSql类? MSDN告诉我使用expression属性，但是我不知道如何将公式转换为表达式.

How can i map a computed column to my LinqToSql Classes? MSDN tells me to use the expression property however i have no idea how to transform my formula into an expression.

我的问题是，一旦我使用SubmitChanges()创建行，除我对象中的计算列外，每个属性都会更新.在其中我需要用于其他任务.

My Problem is that once i create the row using SubmitChanges() every property updates except my computed columns in my object. In which i needed to use for another task.

该公式使用标量sql函数进行计算，在该公式中，该公式计算另一个表中的值之和.我可以转换它，还是必须创建自己的未映射属性来为我计算该属性，还是刷新我的datacontext以获取值?

The formula uses a scalar sql function to compute it, in which it computes the sum of values from another table. Can i convert it or do i have to create my own un-mapped property that computes it for me or refresh my datacontext to get the values?

推荐答案

使用Expression属性，您可以轻松映射计算列，例如...

By using the Expression attribute you can easily map computed columns, for example...

[Table(Name = "Orders")]
class Order
{
     [Column(Storage="Price", DbType="Money",Expression="UnitPrice + 1.00")]
     public decimal Price{ get; set }

     [Column(Storage="Qty", DbType="Int"]
     public int Quantity { get; set; }

     [Column(Storage="Total", DbType="Money",Expression="Price * Quantity")]
     public decimal Total { get; set; }
}

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