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class Program
{
static void Main(string[] args)
{
List<myobject> list = new List<myobject>();
list.Add(new myobject { name = "n1", recordNumber = 1 });
list.Add(new myobject { name = "n2", recordNumber = 2 });
list.Add(new myobject { name = "n3", recordNumber = 3 });
list.Add(new myobject { name = "n4", recordNumber = 3 });
//Generates Row Number on the fly
var withRowNumbers = list
.Select((x, index) => new
{
Name = x.name,
RecordNumber = x.recordNumber,
RowNumber = index + 1
}).ToList();
//Generates Row Number with Partition by clause
var withRowNumbersPartitionBy = withRowNumbers
.OrderBy(x => x.RowNumber)
.GroupBy(x => x.RecordNumber)
.Select(g => new { g, count = g.Count() })
.SelectMany(t => t.g.Select(b => b)
.Zip(Enumerable.Range(1, t.count), (j, i) => new { Rn = i, j.RecordNumber, j.Name}))
.Where(i=>i.Rn == 1)
.ToList();
//print the result
withRowNumbersPartitionBy.ToList().ForEach(i => Console.WriteLine("Name = {0} RecordNumber = {1}", i.Name, i.RecordNumber));
Console.ReadKey();
}
}
class myobject
{
public int recordNumber { get; set; }
public string name { get; set; }
}
结果:
Name = n1 RecordNumber = 1
Name = n2 RecordNumber = 2
Name = n3 RecordNumber = 3