Can't find assembly System? Any idea what this is about?

Question

I have been troubleshooting this all morning. It is a simple extension function that appears to error unable to find system.dll. This is .net 4.0 / OPA 10.3 and the error makes no sense. Can another pair of eyes look at this and try to figure out why the error is occurring?
Thank you.
The Error:
System.IO.FileNotFoundException: Could not load file or assembly 'System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies. The system cannot find the file specified.
File name: 'System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'
at Oracle.Determinations.Text.TestRegEx.TestRegEx.Evaluate(EntityInstance entityInstance, Object[] objects)
at Oracle.Determinations.Engine.Local.Eval.ExpressionCustomFunction.EvaluateSlice(LocalEntityInstance instance, ChangePointDate startDate, ChangePointDate endDate, Object[] Params, Relevance[] relevance)
The extension.xml:
<extension>
<functions>
<function name="TestRegEx" return-type="boolean">
<arg name="entered-name" type="text"/>
<arg name="entered-regex" type="text"/>
<handler platform="dotnet"
class="Oracle.Determinations.Text.TestRegEx.TestRegEx"/>
</function>
</functions>
</extension>
The java class:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Oracle.Determinations.Engine;
using System.Text.RegularExpressions;
namespace Oracle.Determinations.Text.TestRegEx
public class TestRegEx : CustomFunction
public override Object Evaluate(EntityInstance entityInstance, object[] objects)
Regex regex = new Regex((string)objects[1]);
return regex.IsMatch((string)objects[0]);
}

Answer 1

The System.Text.RegularExpressions namespace only exists in the .NET 4 framework. What application are you running? Oracle Policy Modeling 10.3 is a .NET 2 application, so it will load the Determinations Engine into the .NET 2 framework, not the .NET 4 framework.