C#列表比较忽略类项

Question

我有两个数据库 DB1 和 DB2，我从每个数据库中检索销售订单并放入列表中。我现在想在 DB2 中找到 DB1 中缺少的销售订单，以便将它们添加到 DB2 中

我有listDB1 和ListDB2 的形式：

public class SalesOrder
{
      public int docNum;
      public string cardCode;
      public string cardName;
      public DateTime docDate;
      public DateTime docDueDate;                       
      public double docTotal;        
      public int lineItemCount;
      public string comments;
} 

我现在想比较两个列表，忽略两个列表的 docNum，这是在比较其余元素时自动生成的。使用：

unaddedSOs = listDB1.Except(listDB2).ToList();

比较包括 docNum 在内的所有内容。如何实现我需要的，以便获得未添加的文档编号？

Answer 1

您可以实现IEquatable<SalesOrder>，或创建自定义IEqualityComparer<SalesOrder>。请注意，我还建议您将这些公共字段转换为属性。

public class SalesOrder : IEquatable<SalesOrder>
{
    public int DocNum { get; set; }
    public string CardCode { get; set; }
    public string CardName { get; set; }
    public DateTime DocDate { get; set; }
    public DateTime DocDueDate { get; set; }
    public double DocTotal { get; set; }
    public int LineItemCount { get; set; }
    public string Comments { get; set; }

    public bool Equals(SalesOrder other)
    {
        if (ReferenceEquals(null, other)) return false;
        if (ReferenceEquals(this, other)) return true;
        return string.Equals(cardCode, other.cardCode) &&
               string.Equals(cardName, other.cardName) &&
               docDueDate.Equals(other.docDueDate) &&
               docTotal.Equals(other.docTotal) && 
               lineItemCount == other.lineItemCount &&
               string.Equals(comments, other.comments);
    }

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj)) return false;
        if (ReferenceEquals(this, obj)) return true;
        if (obj.GetType() != this.GetType()) return false;
        return Equals((SalesOrder) obj);
    }

    public override int GetHashCode()
    {
        unchecked
        {
            var hashCode = (cardCode != null ? cardCode.GetHashCode() : 0);
            hashCode = (hashCode*397) ^ (cardName != null ? cardName.GetHashCode() : 0);
            hashCode = (hashCode*397) ^ docDueDate.GetHashCode();
            hashCode = (hashCode*397) ^ docTotal.GetHashCode();
            hashCode = (hashCode*397) ^ lineItemCount;
            hashCode = (hashCode*397) ^ (comments != null ? comments.GetHashCode() : 0);
            return hashCode;
        }
    }