C# 更改传入虚拟方法的类型

我有一个关于在虚拟方法中更改参数类型的问题。首先，我将解释这个场景

这是可执行命令的用户的基本界面

public interface IUserThatExecutesCommands
{
   bool IsInRole(string role);
} 

这是基本界面的扩展，要求用户具有卓越的概念

public interface IUserThatExecutesEminenceCommands : IUserThatExecutesCommands
{
   int Eminence { get; }
}

现在，这是一个基本的抽象UserCommand类，它定义了

IUserThatExecutesCommands

使用的命令

public abstract class UserCommand
{
   public virtual bool CanBeExecutedBy(IUserThatExecutesCommands user)
   {
       // For the purpose of simplification I have not included the actual implementation of this method.
       return UserIsInOneOfAllowedRoles(user);
   }
}

下面是该类的扩展，它引入了卓越的概念，因此需要使用

IUserThatExecutesEminenceCommands

。目前，这会导致编译器错误，因为我已更改传入的使用类型

public abstract class EminenceCommand : UserCommand
{
        public override bool CanBeExecutedBy(IUserThatExecutesEminenceCommands user)
        {
            return user.Eminence >= _requiredEminence;
        }
}

我的问题是，是否有一种方法可以覆盖

CanBeExecutedBy

函数，以便更改传入的用户类型？我希望能够扩展UserCommand类，但目前由于这个问题我无法扩展

谢谢

试试这个：

public abstract class EminenceCommand : UserCommand 
{ 
        public override bool CanBeExecutedBy(IUserThatExecutesCommands user) 
        { 
            // Dynamically check the type of user passed in and only check priveleges if correct type
            IUserThatExecutesEminenceCommands u = user as IUserThatExecutesEminenceCommands;
            if( u == null) {
                 return false;
            }
            return u.Eminence >= _requiredEminence; 
        } 
} 

试试这个：

public abstract class EminenceCommand : UserCommand 
{ 
        public override bool CanBeExecutedBy(IUserThatExecutesCommands user) 
        { 
            // Dynamically check the type of user passed in and only check priveleges if correct type
            IUserThatExecutesEminenceCommands u = user as IUserThatExecutesEminenceCommands;
            if( u == null) {
                 return false;
            }
            return u.Eminence >= _requiredEminence; 
        } 
} 

---

一旦你为一个虚拟函数建立了一个签名，它就变成了一个你不能改变的契约。但是，您可以测试

user

参数到

canbeecutedby

并查看它是否支持任何所需的接口。因此，您的方法如下所示：

public override bool CanBeExecutedBy(IUserThatExecutesCommands user)
{
    IUserThatExecutesEminenceCommands u = user as IUserThatExecutesEminenceCommands;
    if (u == null)
    {
        // TODO: Ignore the arg, throw an exception or do something else.
        return false;
    }

    return u.Eminence >= _requiredEminence;
}

---

一旦你为一个虚拟函数建立了一个签名，它就变成了一个你不能改变的契约。但是，您可以测试

user

参数到

canbeecutedby

并查看它是否支持任何所需的接口。因此，您的方法如下所示：

public override bool CanBeExecutedBy(IUserThatExecutesCommands user)
{
    IUserThatExecutesEminenceCommands u = user as IUserThatExecutesEminenceCommands;
    if (u == null)
    {
        // TODO: Ignore the arg, throw an exception or do something else.
        return false;
    }

    return u.Eminence >= _requiredEminence;
}