设置属性时，属性始终具有值吗？ [英] Do properties always have a value when unset?

问题描述

我有一个这样的属性：

public Tuple<String, String>[] Breadcrumbs { get; set; }

我用一种这样的方法进行了测试：

and I have a test in one of my methods like this:

if (Breadcrumbs != null && Breadcrumbs.Length > 0) { }

根据调用此方法的时间，可能未设置面包屑。在一个测试中， Breadcrumbs == null 评估为true。

Depending on when this method is called, Breadcrumbs may not have been set. In one test, Breadcrumbs == null evaulates to true.

未设置的属性将始终具有值吗？ （它将始终为 null ？）

Will unset properties always have a value? (Will it always be null?)

推荐答案

自动实现的未由任何代码明确设置的property始终具有该属性类型的默认值-对于引用类型为null。 （对于 int 它将为0，对于 char 则为'\0'，等等。）

An automatically-implemented property which hasn't been explicitly set by any code will always have the default value for the property type - which is null for reference types. (For int it would be 0, for char it would be '\0' etc).

像这样的自动实现的属性 just 等效于：

An automatically implemented property like this is just equivalent to:

private PropertyType property;
public PropertyType Property
{
    get { return property; }
    set { property = value; }
}

...，只是后备变量的名称难以置信（您可以't在代码中引用它），因此它将始终以该类型的默认值开始。

... except that the backing variable has an unspeakable name (you can't refer to it in code) so it will always start off with the default value for the type.

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