linq的三元运营商 [英] Terniary operator in linq

问题描述

我需要一个三元运算符where where子句linq。



我尝试过：

I need a ternary operator in where clause linq.

What I have tried:

filteredItem = ItemList.Where(x =>; (Model != "" ? (x.ModelNumber.ToLower().Contains(Model.ToLower())) : x.ModelNumber)

推荐答案

在三元运算符中，：每一侧的两个元素都必须返回相同的类型。

在你的代码中显然不是这种情况，左边的部分返回一个布尔值（包含方法），而右边的部分似乎返回一个字符串（ModelNumber）。



请参阅？ ：运算符（C＃参考） [ ^ ]。

特别是本段：

In a ternary operator, both elements in each side of the : must return the same type.
Which is apparently not the case in your code, where the left part returns a boolean (Contains method) whereas the right part seems to return a string (ModelNumber).

Please see ?: Operator (C# Reference)[^].
Especially this paragraph:

Either the type of first_expression and second_expression must be the same, or an implicit conversion must exist from one type to the other.

希望这会有所帮助。

Hope this helps.

这没有任何意义。



您发布的代码执行此操作：

That doesn't make any sense.

The code you posted does this:

if Model does not equal ""
    // This will return a boolean value.
    return (x.ModelNumber.ToLower().Contains(Model.ToLower())
else
    // This will return whatever ModelNumber is.
    return x.ModelNumber

我非常怀疑你的ModelNumber是一个布尔值，所以你的两个返回类型是不同的。在三元操作中，这是一个灾难的处方。

I highly doubt your ModelNumber is a boolean so your two return types are different. In a Ternary operation, that is a recipe for disaster.

从您的代码我猜你正在尝试同时过滤和修改你的代码，这通常是不可能的开箱即用。



如果我正确理解你的片段，你想要返回一个ModelNumber属性，如果Model不是空的并且它当前包含它迭代元素。



这是一个可能的解决方案：

From your code I am guessing that you are trying to filter and modify your code at the same time, which usually is not possible to do out of the box.

If I understood you snippet correctly you want to return a "ModelNumber" property if "Model" is not empty and it is contained it currently iterated element.

Here is a possible solution:

var filteredItems =
                string.IsNullOrWhiteSpace(Model)
                    ? ItemList
                    : ItemList.Where(x => x.ModelNumber.ToLowerInvariant().Contains(Model.ToLowerInvariant())).ToList();

希望这会有所帮助，祝你好运，下次请尝试更具体，或向我们展示更多代码。



干杯！

Hope this helps, good luck and next time please try to be more specific, or show us more code.

Cheers!

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