如何覆盖 C# 中列表的包含属性？

Question

我有一个对象 List<IReportRelationMapping> 的列表，我需要检查该列表是否不包含特定的 ReportRelationMapping 对象

这是我的ReportRelationMapping 的样子

public class ReportRelationMapping : IReportRelationMapping
{
     public string Name { get; set; }

     public IReportRelation LocalRelation { get; set; }

     public IReportRelation ForeignRelation { get; set; }

     public IReportRelationMapping RelatedThrough { get; set; }
}

列表包含一个对象 if this.LocalRelation == passed.LocalRelation && this.ForeignRelation == passed.ForeignRelation 或 this.LocalRelation == passed.ForeignRelation && this.ForeignRelation == passed.LocalRelation

这是我为覆盖列表的Contains 属性所做的操作

public class ReportRelationMapping : IReportRelationMapping
{
    public string Name { get; set; }

    public IReportRelation LocalRelation { get; set; }

    public IReportRelation ForeignRelation { get; set; }

    public IReportRelationMapping RelatedThrough { get; set; }

    public bool Equals(ReportRelationMapping other)
    {
        if (other == null)
        {
            return false;
        }

        if (object.ReferenceEquals(this, other))
        {
            return true;
        }

        if (this.GetType() != other.GetType())
        {
            return false;
        }

        return (this.LocalRelation == other.LocalRelation && this.ForeignRelation == other.ForeignRelation)
            || (this.LocalRelation == other.ForeignRelation && this.ForeignRelation == other.LocalRelation);
    }

    public override bool Equals(object other)
    {
        if (other == null)
        {
            return false;
        }

        if (object.ReferenceEquals(this, other))
        {
            return true;
        }

        if (this.GetType() != other.GetType())
        {
            return false;
        }

        return this.Equals(other as ReportRelationMapping);
    }

    public override int GetHashCode()
    {
        int hash = 14;
        hash = (hash * 7) + this.ForeignRelation.GetHashCode();
        return (hash * 7) + this.LocalRelation.GetHashCode();
    }

    public static bool operator ==(ReportRelationMapping lhs, ReportRelationMapping rhs)
    {
        // Check for null on left side. 
        if (Object.ReferenceEquals(lhs, null))
        {
            if (Object.ReferenceEquals(rhs, null))
            {
                // null == null = true. 
                return true;
            }

            // Only the left side is null. 
            return false;
        }
        // Equals handles case of null on right side. 
        return lhs.Equals(rhs);
    }

    public static bool operator !=(ReportRelationMapping lhs, ReportRelationMapping rhs)
    {
        return !(lhs == rhs);
    }

}

但由于某种原因，即使列表包含给定对象，我也会得到false 或“不包含该对象”。当我调试我的代码时，我可以看到调试器到达Equal 方法，所以它通过我的代码，但它永远不会到达GetHashCode 方法。我不确定我是否在这里错误地实现了我的GetHashCode 方法。

我在这里错过了什么？在我的情况下，为什么包含总是返回“不包含”？ 如何正确覆盖列表的 Contains 方法？

Answer 1

您可能应该通过调用Enumerable.Any() 来执行此操作，如下所示：

bool contains = myList.Any(t =>
    (t.LocalRelation == passed.LocalRelation && t.ForeignRelation == passed.ForeignRelation)
    || (t.LocalRelation == passed.ForeignRelation && t.ForeignRelation == passed.LocalRelation)

无需覆盖Equals 或任何其他内容。

或者，如果您不想使用 Enumerable (LINQ)，可以使用 List.Exists 方法，您可以以相同的方式调用：

bool contains = myList.Exists(t =>
    (t.LocalRelation == passed.LocalRelation && t.ForeignRelation == passed.ForeignRelation)
    || (t.LocalRelation == passed.ForeignRelation && t.ForeignRelation == passed.LocalRelation)