C＃列表比较忽略类项

Question

I have two databases DB1 and DB2 where I am retrieving sales orders from each and into lists. I now want to find the sales orders that are missing in DB2 that are in DB1 so that they are added to DB2

I have listDB1 and ListDB2 in the form:

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;
} 

I now want to compare the 2 lists ignoring the docNum for both lists which is auto-generated while comparing the rest of the elements. Using:

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

compares all including docNum. How do I achieve what I need so I can get the doc Numbers that are unadded?

Answer 1

You can either implement IEquatable<SalesOrder> , or create a custom IEqualityComparer<SalesOrder> . Note i'd also advise you to turn those public fields into properties.

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;
        }
    }