Having issue with Spring Expression, unable to get expression to evaluate an instance

I am unable to get any expression to work that evaluates an instance of a custom class, using an alias.

[Expression]
PtnStats.Key == #BNSum

[Variables]
BNSum = "0"

[typeAliases]
<typeAliases>
<alias name="Game" type="UltimateLotteryLib.BLL.Game, UltimateLotteryLib.Common" />
<alias name="NumHst" type="UltimateLotteryLib.BLL.NumberHistory, UltimateLotteryLib.Common" />
<alias name="NumStats" type="UltimateLotteryLib.BLL.NumberHistoryStatisti csII, UltimateLotteryLib.Common" />
<alias name="GblStats" type="UltimateLotteryLib.Stats.NumberStatistics, UltimateLotteryLib.Stats" />
<alias name="ColStats" type="UltimateLotteryLib.Stats.ColumnStatistics, UltimateLotteryLib.Stats" />
<alias name="PtnStats" type="UltimateLotteryLib.Stats.GlobalPatternStatis tics, UltimateLotteryLib.Stats" />
</typeAliases>

[Code]
var result = new object();
object instance = new object();

var expr_final = "PtnStats.Key == #BNSum";

instance = new GlobalPatternStatistics();

result = ExpressionEvaluator.GetValue(instance, expr_final, vars); // Invalid Cast Exception occurs when calling this function.