是否可以使用其他变量类型设置类变量 [英] Is it possible to set a class variable using a different variable type

问题描述

是否可以为c#变量设置与变量类型设置不同的变量类型值?

is it possible to set a c# variable with a different variable type value than what the variable one is setting?

public class Test{

   public DateTime TimeSinceEpoch {
      get {return TimeSinceEpoch; }
      set{ 
         DateTime Epoch = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
         TimeSinceEpoch = Epoch.AddMilliseconds(value);}} //<-the value that's expected is a DateTime value..
}

我该怎么写:'TimeSinceEpoch = 1549090800000'并将TimeSinceEpoch用作普通的DateTime变量?

How can i write: 'TimeSinceEpoch = 1549090800000' and use TimeSinceEpoch as a normal DateTime variable?

无需在类内单独获取和设置变量

推荐答案

即使在 具有语法的C ++/CLI中，也不允许这样做:

This isn't allowed even in C++/CLI which does have a syntax for it:

public ref struct Test
{
    property System::DateTime TimeSinceEpoch
    {
        DateTime get();
        void set(DateTime);
        void set(long long);
    }
};

您收到以下错误:

错误C3902:'设置':最后一个参数的类型必须为'System :: DateTime'

error C3902: 'set': type of last parameter must be 'System::DateTime'

Intellisense实际上会产生两个投诉，具体取决于您编写投诉的顺序:

Intellisense actually produces two complaints, depending on which order you write them:

E1930:已经在此属性中为此属性声明了设置"访问器

E1930: a 'set' accessor was already declared for this property at

或

E1942:设置"访问器的最后一个参数与属性类型不匹配

E1942: the last parameter of the 'set' accessor does not match the property type

潜在的问题是.NET属性必须在元数据中列出类型和最多一个setter(请查看

The underlying problem is that a .NET property has to list a type and a maximum of one setter in the metadata (Have a look at PropertyInfo.GetSetMethod -- it returns one setter or null, not an array). Even though you could easily overload the setter function itself:

void set_TimeSinceEpoch(DateTime)
void set_TimeSinceEpoch(long)

这两个功能中只有一个可以与该属性相关联.

only one of these two functions could be associated to the property.

您可以使用助手类型来允许多种传入类型:

You could use a helper type to allow multiple incoming types:

struct SuperDateTime
{
    public DateTime Value;
    public static implicit operator SuperDateTime(DateTime d) { return new SuperDateTime { Value = d }; }
    public static implicit operator SuperDateTime(long x) { return new SuperDateTime { Value = Epoch.AddMilliseconds(x) }; }
    public static implicit operator DateTime(SuperDateTime d) { return d.Value; }
}

但这会破坏该属性的读者，他们现在必须在使用成员之前说 TimeSinceEpoch.Value (如果将其作为参数传递给另一个函数，则隐式转换将开始).为了克服这个问题，您需要为 DateTime 的每个成员编写转发功能.

but this will break readers of the property, who now have to say TimeSinceEpoch.Value before using a member (if passing as an argument to another function, the implicit conversion will kick in). To overcome that, you'd need to write a forwarding function for every single member DateTime has.

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