c# - 并非所有代码路径都会在方法中返回带有输出参数的值

Question

我正在练习构建一个虚拟应用程序，我正在尝试传入一个枚举作为参数，并有一个整数输出参数，该参数将用于设置成员变量( BillsOwed )。我有两个具体问题:为什么是ComputeRetirementBenefitCost告诉我我的变量 must be assigned to before control leaves the current method为什么不是 ComputeRetirementBenefitCost可以访问我在评论中标记的位置吗？欢迎任何和所有谨慎的 future 设计建议:)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace GivePromotions
{
    //Different Employees in the EmpType enum extend this class
    public abstract class Employee
    {
        public int EmployeeId { get; set; }
        public string LastName { get; set; }
        public string FirstName { get; set; }
        public DateTime DateHired { get; set; }
        public RetirementPackage.RetirementPackageType PackageType { get; set; }
        public EmpType Employeetype { get; set; }
        public int NetSalary { get; set; }

        //I'd like to set the output of ComputeRetirementBenefitCost
        //in the member below but Intellisense doesn't pick it up
        //on two lines for space, commented because it doesn't work  
        //int billsOwed = Employee.RetirementPackage
        //.ComputeRetirementBenefitCost(Employee.EmpType,out benefitCost)
        public virtual void DisplayInformation()
        {
            Console.WriteLine("Employee information: ");
            Console.WriteLine("EmployeeId = {0} ", EmployeeId);
            Console.WriteLine("Last name  = {0} ", LastName);
            Console.WriteLine("First name = {0} ", FirstName);
            Console.WriteLine("Date hired = {0} ", DateHired);
            Console.WriteLine("Salary     = {0} ", NetSalary);
        }

        public enum EmpType
        {
            Janitor,
            President,
            Manager
        }



        //an Employee 'has-a' Retirement package
        public class RetirementPackage
        {

            public enum RetirementPackageType
            {
                Basic,
                Gold,
                Silver,
                Platinum,
                Black
            }
        //method of choice here 
        //ERROR: Output parameter 'benefitCost' must be assigned to before control
        //leaves the current method
        public void ComputeRetirementBenefitCost(Employee.EmpType e, out int benefitCost)
        {   

                switch (e)
                {
                    case Employee.EmpType.President:
                         benefitCost = 100000;
                         break;
                    case Employee.EmpType.Manager:
                         benefitCost = 5000;
                         break;
                    case Employee.EmpType.Janitor:
                         benefitCost = 1000;
                         break; 



                }


            }

        }
    }


}

Answer 1

• 错误:输出参数“benefitCost”必须在控制之前分配给:

您必须向开关添加“默认值:”或在开关外部设置一个值，因为这三种情况可能都不会被命中。

• 为什么 ComputeRetirementBenefitCost 不可访问

解决第一个问题就可以解决这个问题。 使用 crtl+shif+B 构建并读取错误 ListView 中的错误和警告。通常他们会告诉您到底出了什么问题。