c# - 为什么 name 在当前的速记成员初始化上下文中不存在？

Question

我正在为 st 对象使用对象初始值设定项:

public class Container 
{
    public Container () { ContainedItem = new Item; }
    public Item ContainedItem { get; set; }
}

public class Item
{
    public string Value { get; set; }
}

var MyContainer = new Container()
{
    // I want to populate the the property Value of the property Item
    // with the second line rather than the first
    ContainedItem = new Item() { Value = FooString }, // This works
    ContainedItem.Value = FooString  // This assigns to the same member but does not work
};

第二个初始化行给出了错误:

The name 'ContainedItem' does not exist in the current context.

Invalid initializer member declarator.

并建议在局部范围内的某处声明 ContainedItem。

现在第一行可以看到 ContainedItem 实际上是 Container 的一个有效属性并且 MyContainer.ContainedItem 是绝对不是 null...那么为什么下面这行无法识别它呢？

Answer 1

内联对象初始化的语法有明确规定。您不能只是编造东西并期望编译器能够理解。语法是严格的:

{
    Property1 = Value1,
    Property2 = Value2,
    ...
}

c.x不是 st 的属性(property). c是。因此，你不能说 c.x = Bar[i].x

来自 C# 语言规范部分 7.6.10.2:


object-initializer:
<br/>
{ member-initializer-listopt }

{ member-initializer-list , }
member-initializer-list:

member-initializer

member-initializer-list , member-initializer
member-initializer:

identifier = initializer-value
initializer-value:

expression

object-or-collection-initializer