英文:
new() usage in methods for C#
问题
给属性赋值new()到底意味着什么呢？我发现一些例子中在方法调用中看到了new的使用，但不像下面这样。
public ObservableCollection<Customer> Customers { get; } = new();
英文:
What exactly does it mean when assigning new() to a property?
I found some examples of seeing new usage in method calls but not like the below.
public ObservableCollection<Customer> Customers { get; } = new();
答案1
得分: 5
这是target-typed new，实际上它将创建一个与操作数左侧的对象。
在自动属性的情况下，它将分配一个该属性类型的新实例给该属性。
所以，如果我们去掉所有的语法糖，你实际上得到的是：
private ObservableCollection<Customer> _customers = new ObservableCollection<Customer>();
public ObservableCollection<Customer> Customers
{
get
{
return _customers;
}
}
顺便说一下，几乎在任何已知类型存在的地方，都可以使用目标类型的 new，不仅限于自动属性。
英文:
It's target-typed new, essentially it will create an object of whatever the left of the operand is.
In the case of auto-properties, it will assign a new instance of the type of that property, to the property.
So if we strip away all of the syntactic sugar, what you've essentially got is:
private ObservableCollection<Customer> _customers = new ObservableCollection<Customer>();
public ObservableCollection<Customer> Customers
{
get
{
return _customers;
}
}
Incidentally, you can use a target-typed new almost anywhere there's a well-known type, not just on auto-properties.
答案2
得分: 3
这是一个目标类型的new表达式（在C# 9中引入），等同于：
public ObservableCollection<Customer> Customers { get; } = new ObservableCollection<Customer>();
所以Customers是自动实现的属性，其初始化为新创建的ObservableCollection<Customer>实例。
英文:
This is a target-typed new expression (introduced in C# 9) and is equivalent to:
public ObservableCollection<Customer> Customers { get; } = new ObservableCollection<Customer>();
So the Customers is an auto implemented property which initialized to a newly created instance of ObservableCollection<Customer>.
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