vb.net - 为什么赋值运算符在 VB.NET 中不可重载？

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已关闭 11 年前。

为什么赋值运算符(+=、-=、*=、/=)在 VB.NET 中不能重载？

Answer 1

也许this他们的理由是:

Thanks for the suggestion! We don't allow you to overload the assignment operator for a type because there is currently no way to ensure that other languages or the .NET Framework itself will honor the assignment operator. The only alternative is to restrict what types that overload the assignment operator can do, but we felt that this would be too restrictive to be generally useful.

Thanks! Paul Vick Technical Lead, VB

有一种叫做“缩小”和“扩大”的东西，它允许您定义从一种类型到另一种类型的显式和隐式转换器，即

Dim y as MyClass1
Dim x as MyClass2 = y

但这不允许更改用于分配同一类的实例的赋值运算符，而只能转换其他类。

参见How to: Define a Conversion Operator

Class MyClass1
    Public Shared Widening Operator CType(ByVal p1 As MyClass1) As MyClass2

    End Operator
End Class

<小时/>

Same in C#

+=, -=, *=, /=, %=, &=, |=, ^=, <<=, >>=

Assignment operators cannot be overloaded, but +=, for example, is evaluated using +, which can be overloaded.

=, ., ?:, ??, ->, =>, f(x), as, checked, unchecked, default, delegate, is, new, sizeof, typeof

These operators cannot be overloaded.

同conversion operators :

struct MyType1
{
    ...
    public static explicit operator MyType1(MyType2 src)  //explicit conversion operator
    {
        return new MyType1 { guts = src.guts };
    }
}