Better way for average of duplicates in datatable

//using LiqPad4
void Main()
{
	List<myobject> objts = new List<myobject>{
					new MyObject("a", "a1", "a2", 10),
					new MyObject("b", "b1", "a3", 20),
					new MyObject("a", "a1", "a2", 30),
					new MyObject("a", "b1", "a3", 10)
					};
	
	var qry = from o in objts
			group o by new{o.Column1, o.Column2, o.Column3} into grp
			select new{
				Col1 = grp.Key.Column1,
				Col2 = grp.Key.Column2,
				Col3 = grp.Key.Column3,
				AvgCol4 = grp.Average(p=>p.Column4)
			};
	qry.Dump();
}

// Define other methods and classes here
class MyObject
{
	private string sCol1 = string.Empty;
	private string sCol2 = string.Empty;
	private string sCol3 = string.Empty;
	private int iCol4 = 0;
	
	public MyObject(string _Col1, string _Col2, string _Col3, int _Col4)
	{
		sCol1 = _Col1;
		sCol2 = _Col2;
		sCol3 = _Col3;
		iCol4 = _Col4;
	}

	public string Column1
	{
		get{return sCol1;}
		set{sCol1=value;}
	}
	public string Column2
	{
		get{return sCol2;}
		set{sCol2=value;}
	}
	public string Column3
	{
		get{return sCol3;}
		set{sCol3=value;}
	}
	public int Column4
	{
		get{return iCol4;}
		set{iCol4=value;}
	}
}

Col1 Col2 Col3 AvgCol4
a    a1    a2    20 
b    b1    a3    20 
a    b1    a3    10