c# - 不使用派生类中的方法

Question

Uni 作业要求我们用 C# 构建一个派生 Sauce 的披萨应用程序来自Ingredient 。我有一个List<Ingredient>即存储两种类型的对象。

Pizza.cs调用方法GetInstructions()这与派生方法略有不同。不幸的是Sauce.GetInstructions()永远不会被调用。正如您所看到的，其中有一个调试行，当程序执行该例程时，应该会弹出一个消息框，但它没有弹出。谁能建议为什么不呢？

Pizza.cs包含以下方法:

public string BuildInstructionList()
    {   // iterate through list of selected toppings and build a single string for display in the GUI
    int count = 1; string instructions = "";
    foreach (var i in toppings)
        {
        instructions = instructions += string.Format("Step {0}: {1}", count, i.GetInstructions());
        count++;
        }
        return instructions;
    }

Ingredient.cs包含:

public virtual string GetInstructions()
    {
        string instructionLine;
        string qty = this.GetIngredientQuantity().ToString();
        string unit = this.GetIngredientUnit();
        string name = this.GetIngredientName();
        instructionLine = string.Format("Add {0} {1} of {2} to the pizza.\n", qty, unit, name);
        return instructionLine;
    }

Sauce.cs包含:

public new string GetInstructions()
    {
        PizzaGUI.Message("I am here!");
        string instructionLine;
        string qty = this.GetIngredientQuantity().ToString();
        string unit = this.GetIngredientUnit();
        string name = this.GetIngredientName();
        instructionLine = string.Format("Apply {0} {1} of {2} to the pizza.\n", qty, unit, name);
        return instructionLine;
    }

Answer 1

您需要在 Sauce.cs 方法中使用 override 代替 new。

来自MSDN override 修饰符扩展基类方法，new 修饰符隐藏它。

public override string GetInstructions()
    {
        PizzaGUI.Message("I am here!");
        string instructionLine;
        string qty = this.GetIngredientQuantity().ToString();
        string unit = this.GetIngredientUnit();
        string name = this.GetIngredientName();
        instructionLine = string.Format("Apply {0} {1} of {2} to the pizza.\n", qty, unit, name);
        return instructionLine;
    }