c# - C#中不同的对象列表

Question

我必须区分对象列表，而不仅仅是ID，因为有时两个不同的对象具有相同的ID。
我有课：

public class MessageDTO
{

    public MessageDTO(MessageDTO a)
    {
        this.MsgID = a.MsgID;
        this.Subject = a.Subject;
        this.MessageText = a.MessageText;
        this.ViewedDate = a.ViewedDate;
        this.CreatedDate = a.CreatedDate;
    }

    public int? MsgID { get; set; }
    public string Subject { get; set; }
    public string MessageText { get; set; }
    public System.DateTime? ViewedDate { get; set; }
    public System.DateTime? CreatedDate { get; set; }
}

如何区分以下内容：

List<MessageDTO> example;

谢谢

Answer 1

使用LINQ。

public class MessageDTOEqualityComparer : EqualityComparer<MessageDTO>
{
    public bool Equals(MessageDTO a, MessageDTO b)
    {
        // your logic, which checks each messages properties for whatever
        // grounds you need to deem them "equal." In your case, it sounds like
        // this will just be a matter of iterating through each property with an
        // if-not-equal-return-false block, then returning true at the end
    }

    public int GetHashCode(MessageDTO message)
    {
        // your logic, I'd probably just return the message ID if you can,
        // assuming that doesn't overlap too much and that it does
        // have to be equal on the two
    }
}

然后

return nonDistinct.Distinct(new MessageDTOEqualityComparer());

您还可以通过覆盖 object.Equals(object)和 object.GetHashCode()并调用 nonDistinct.Distinct()的空重载来避免需要额外的类。但是，请确保您了解此决定的含义：例如，这些将在其使用的所有非显式范围内变为相等性测试功能。这可能是完美的，正是您所需要的，否则可能会导致一些意外的后果。只要确保您知道自己正在进入什么。