c# - 动态改变lambda表达式的主体？

Question

示例我有以下代码

public class Person
{
    public bool FirstNameIsActive { get; set; }
    public bool SecondNameIsActive { get; set; }
}    

如果我想按属性过滤FirstNameIsActive

Func<Person, bool> predicate1 = x => x.FirstNameIsActive == true;

如果我想按属性过滤SecondNameIsActive

Func<Person, bool> predicate2 = x => x.SecondNameIsActive == true;

我想在运行时将我的谓词更改为

Func<Person, bool> predicate = x => x.PropertyThatIWant == true;

Answer 1

您可以利用修改后的闭包。

//property selector
Func<Person, Boolean> propertySelector = person => person.FirstNameIsActive;

//your predicate
Func<Person, Boolean> predicate = person => propertySelector(person) == true;

//new person with true, false properties.
Person p = new Person() {FirstNameIsActive = true,SecondNameIsActive = false};

Console.WriteLine(predicate(p).ToString()); //prints true

//change the property selector
propertySelector = person => person.SecondNameIsActive;

//now the predicate uses the new property selector
Console.WriteLine(predicate(p).ToString()); //prints false