LINQ中长类型的求和方法 [英] Sum method in LINQ with long type

问题描述

如何获取长型项目的总和...这是mycode:

How can I get sum of some items in long type... here is mycode :

using (gEn myEntities = new gEn)
{
var load = (from items in myEntities.Orders
select items.PayO).DefaultIfEmpty(0).Sum();
}

但是Sum给我一个整数...我也想知道DefaultIfEmpty方法与Sum方法在长类型中使用时是否有冲突...预先感谢...

but the Sum gives me int... I also wants to know if DefaultIfEmpty method has any conflict with Sum method when use it for long type... thanks in advance...

推荐答案

Sum 返回select中使用的表达式返回的任何类型(前提是它是已定义的重载之一).如果要返回很长的时间，则强制转换items.PasO:

Sum returns whatever type the expression used in the select returns (provided it's one of the defined overloads). If you want to return a long then cast items.PasO:

var load = (from items in myEntities.Orders
select (long)(items.PayO)).DefaultIfEmpty(0).Sum();

我还想知道DefaultIfEmpty方法用于长型时是否与Sum方法有冲突

I also wants to know if DefaultIfEmpty method has any conflict with Sum method when use it for long type

否，DefaultIfEmpty适用于 any 类型，包括long.只要该类型存在Sum重载，它就可以正常工作.

No, DefaultIfEmpty works with any type, including long. As long as there's a Sum overload for that type it works just fine.

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