c# - 有条件地限制属性(property)访问

Question

是否有更好的方法来限制对职业和雇主属性的访问？

此类只是为了收集一个人(潜在客户)的就业信息而设计的。就业状态可以是就业、自雇、失业、退休等...

我只希望此类用户能够在该人确实受雇的情况下设置雇主和职业。

public class EmploymentInformation
{
    private const string _EmploymentStatusNotEmployedMessage = "Employment status is not set to employed";

    private string _occupation;

    private Company _employer;

    /// <summary>The person's employment status<example>Employed</example></summary>
    public EmploymentStatus EmploymentStatus { get; set; }

    /// <summary>The person's occupation<example>Web Developer</example></summary>
    public string Occupation
    {
        get
        {
            if (IsEmployed)
            {
                return _occupation;
            }
            throw new ApplicationException(_EmploymentStatusNotEmployedMessage);
        }

        set
        {
            if (IsEmployed)
            {
                _occupation = value;
            }
            throw new ApplicationException(_EmploymentStatusNotEmployedMessage);
        }
    }

    /// <summary>The person's employer</summary>
    public Company Employer
    {
        get
        {
            if (IsEmployed)
            {
                return _employer;
            }
            throw new ApplicationException(_EmploymentStatusNotEmployedMessage);
        }

        set
        {
            if (IsEmployed)
            {
                _employer = value;
            }
            throw new ApplicationException(_EmploymentStatusNotEmployedMessage);
        }
    }

    private bool IsEmployed
    {
        get
        {
            return EmploymentStatus == EmploymentStatus.Employed 
                || EmploymentStatus == EmploymentStatus.SelfEmployed;
        }
    }

    /// <summary>
    /// Constructor for EmploymentInformation
    /// </summary>
    /// <param name="employmentStatus">The person's employment status</param>
    public EmploymentInformation(EmploymentStatus employmentStatus)
    {
        EmploymentStatus = employmentStatus;
    }
}

Answer 1

如果未设置值，仅返回 null 有什么问题吗？这是相当常见的做法。如果Employer不存在，则其值为空。为什么它是 null 可能不相关。此外，还强制在类本身的 ctor 内设置就业状态。