接口成员不能有定义

Question

为什么我无法添加此接口的默认实现？

我有 C# 8 / .NET Core 3.0（如 Main 中所示）

但出于某种原因它大喊：

'ITest.Test()': interface members cannot have a definition

interface ITest
{
    // Interface members cannot have a definition
    void Test()
    {
        Console.WriteLine("Interface");
    }
}

public class Test : ITest
{
    void ITest.Test()
    {
        throw new NotImplementedException();
    }
}
class Program
{
    static void Main(string[] args)
    {
        // this works properly
        var arr = "test".ToCharArray();

        Console.WriteLine(arr[1..2]);
        Console.WriteLine(arr[..2]);
        Console.WriteLine(arr[..^1]);
        Console.WriteLine(arr[^1..]);
    }
}

Answer 1

默认接口方法功能是 not available yet, even in the C# 8.0 preview（微软代表在回复 "Rand.Random" 评论者询问此功能未在预览中时确认）。

如果你想提供一个实现，我会推荐使用继承和虚拟方法。

public class TestBase
{
    public virtual void TestMethod()
    {
        Console.WriteLine("TestBase");
    }
}

public class Test : TestBase
{
    public override void TestMethod()
    {
        throw new NotImplementedException();
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        var testBase = new TestBase();
        testBase.TestMethod(); // Prints "TestBase"

        var test = new Test();
        test.TestMethod(); // Throws NotImplementedException
    }   
}

Answer 2

因为这个功能还不可用。根据 C# 8.0 测试版 dymanoid's link, this feature is in the prototype stage. It's not mentioned in the blog post。

接口成员不能有定义

Interface members cannot have a definition

c#

c#-8.0