在Linq中传递参数 [英] Passing a parameter within Linq

问题描述

我在方法中包含以下代码:

I have the following code within a method:

someData = table.AsEnumerable()
    .Where(row => row.someRow.Equals("Something"))
    .Sum(row => row.AnotherRow);

在最后一行，我想从其他地方传递一个参数，该参数将替换.AnotherRow

On the last line I want to pass in a parameter from somewhere else which will replace .AnotherRow

换句话说，是这样的:

.Sum(row => row. + myParameter);

有什么想法吗?尝试上述操作时出现错误.不胜感激.

Any ideas? I get an error when I try the above. Would appreciate any help.

推荐答案

您不能传递表示.AnotherRow的内容，但是可以传递函子，该函子从对象中选择所需的属性.

You cannot pass something that would represent .AnotherRow, but you can pass a functor that picks the desired attribute from your object.

让我们说table是IEnumerable<MyClass>.然后，您可以执行以下操作:

Let's say table is IEnumerable<MyClass>. Then you can do this:

int SumSelected(Func<MyClass,int> attrSelector) {
    return table.AsEnumerable()
        .Where(row => row.someRow.Equals("Something"))
        .Sum(row => attrSelector(AnotherRow));
}

现在，您可以使用选择器"来调用此方法，该选择器指定要添加的属性，如下所示:

Now you can call this method with a "selector" that designates the attributes to be added up, as follows:

var totalCustomers = SumSelected(obj => obj.CustomerCount);
var totalStores = SumSelected(obj => obj.StoreCount);

这篇关于在Linq中传递参数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！