c# - 与我类(class)的名单不同

Question

我有一个类:

private class Part
{
    public string Id { get; set; }
    public string Class { get; set; }

    public override bool Equals(object obj)
    {
        Part part = obj as Part;

        return this.Id == part.Id;
    }
}

我还有一个这个类的列表，所以我需要在这个列表上使用 distinct。这就是我所做的:

List<Part> parts = new List<Part>();
//adding items
parts = parts.Distinct().ToList();

但是没有任何反应。谁能告诉我怎么了？

Answer 1

当覆盖 Equals 时，您还必须覆盖 GetHashCode:

private class Part
{
    public string Id { get; set; }
    public string Class { get; set; }

    // Whenever overiding Equals
    // You have to override this method too
    public override int GetHashCode() {
      return String.IsNullOrEmpty(Id) ? 0 : Id.GetHashCode();
    }

    public override bool Equals(object obj)
    {
        Part part = obj as Part;

        // if obj is not of Part you should return false
        if (Object.ReferenceEquals(null, part))
          return false; 

        return this.Id == part.Id;
    }
}

不当行为的原因是 Distinct first tests GetHashCode并且只有这样 Equals。