Linq 中的分组（在多个字段上）

Question

我使用 linq 对一些数据进行分组，如下所示：

var groupedData = from row in salesTable.AsEnumerable()                   
group row by   
row.Field<string>("InvoiceNum") into grp
select grp;

我想使用一些字段重新分组 groupedData ，例如 row.Field("InvoiceNum") 、 row.Field("InvoiceLineNum") ，我不知道 linq 分组如何处理多个字段？

Answer 1

使用匿名类型的对象进行分组。

 var groupedData = from row in salesTable.AsEnumerable()                   
                   group row by new
                   {
                        InvoiceNum = row.Field<string>("InvoiceNum"),
                        InvoiceLineNum = row.Field<string>("InvoiceLineNum")
                   }
                   into grp
                   select grp;

或使用命名类

public class InvoiceGrouping : IEquatable<InvoiceGrouping>
{
     public string InvoiceNum { get; set; }
     public string InvoiceLineNum { get; set; }

     public bool Equals( InvoiceGrouping other )
     {
         return other != null 
                && this.InvoiceNum == other.InvoiceNum
                && this.InvoiceLineNum == other.InvoiceLineNum;
     }

     public override bool Equals( object other )
     {
         return Equals( other as InvoiceGrouping );
     }

     public override int GetHashCode()
     {
         unchecked
         {
            int hash = 17;
            hash *= (this.InvoiceNum != null ? 23 + this.InvoiceNum.GetHashCode() : 1);
            hash *= (this.InvoiceLineNum != null ? 23 + this.InvoiceLineNum.GetHashCode() : 1 );
            return hash;
         }
     }
 }

 var groupedData = from row in salesTable.AsEnumerable()                   
                   group row by new InvoiceGrouping
                   {
                        InvoiceNum = row.Field<string>("InvoiceNum"),
                        InvoiceLineNum = row.Field<string>("InvoiceLineNum")
                   }
                   into grp
                   select grp;