使用隐式类型转换调用函数

Question

我有一个class这样的。

public class ForeignKey {
    public string Id {get;}
    public TableA TableA {get;}
    public TableB TableB {get;}
    public static implicit operator string(ForeignKey obj){ return obj.Id; }
    public override string ToString() { return Id; }
    /* various operator overloads */
}

我想对其进行自动类型转换，这样我就可以像字符串一样使用它。到目前为止我所做的让我可以在很多地方使用它而无需显式转换。但是，我想不出不进行显式转换就调用字符串函数的方法。

例如，我想让它工作。

if (Key.EndsWith(someValue))

目前我必须这样做

if (((string)Key).EndsWith(someValue))
// or
if (Key.Id.EndsWith(someValue))

有没有办法让它按照我想要的方式工作？

谢谢

Answer 1

您可以create a extension method将此Key作为参数。

namespace ExtensionMethods
{
  public static class Utilities
  {
    public static bool ValueEndsWith(this Key key, ref string valueToCheck)
    {
      return key.Id.EndsWith(valueToCheck);
    } 
  }
}

你可以这样称呼它 Key.ValueEndsWith(ref valueString);

Answer 2

这无法完成，因为成员查找运算符 . 不考虑除 ForeignKey 之外的其他类型的成员。

第 7.4 节解释了该过程。

A member lookup of a name N with K type parameters in a type T is processed as follows:

First, a set of accessible members named N is determined

Next, if K is zero, all nested types whose declarations include type parameters are removed. If K is not zero, all members with a different number of type parameters are removed.

Next, if the member is invoked, all non-invocable members are removed from the set.

Next, members that are hidden by other members are removed from the set.

Next, interface members that are hidden by class members are removed from the set. This step only has an effect if T is a type parameter and T has both an effective base class other than object and a non-empty effective interface set.

Finally, having removed hidden members, the result of the lookup is determined:

If the set consists of a single member that is not a method, then this member is the result of the lookup.

Otherwise, if the set contains only methods, then this group of methods is the result of the lookup.

Otherwise, the lookup is ambiguous, and a binding-time error occurs.

由于 C# 在成员解析过程中不考虑转换运算符，您唯一的选择是直接或通过扩展将方法添加到您的 class。

使用隐式类型转换调用函数

Call Function with Implicit Type Conversion

c#

implicit-conversion