LINQ Group由VB.Net中的多个属性组成

我花了很多时间在这个问题上.我可以做简单的Group By LINQ查询(在一个属性上),但是对于多个字段我有点卡住了
这是一个LINQPad我想要做的样品：

dim lFinal={new with {.Year=2010,.Month=6,.Value1=0,.Value2=0},new with {.Year=2010,.Value1=2,.Value2=1},.Month=7,.Value1=3,.Value2=4},.Month=8,new with {.Year=2011,.Month=1,.Value2=2},.Value2=0}}

Dim lFinal2 = From el In lFinal
              Group el By Key = new with {el.Year,el.Month}
              Into Group
              SELEct New With {.Year = Key.Year,.Month=Key.Month,.Value1 = Group.Sum(Function(X) x.Value1),.Value2 = Group.Sum(Function(X) x.Value2)}

lFinal.Dump()
lFinal2.Dump()

lFinal列表有6个项目,我想要lFinal2有4个项目：2010-6和2011-1应该组合.

提前致谢.

= Group el By Key = new with {el.Year,el.Month}

= Group el By Key = new CustomKey() { Year = el.Year,Month = el.Month };

public class CustomKey{
    int Year { get; set; }
    int Month { get; set; }

    public override bool Equals(obj A) {
        var key (CustomKey)A;
        return key.Year == this.Year && key.Month == this.Month;
    }
}