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    <p>So the error I was running into was all the examples I read in trying to find out how to access sub properties were using MemberAccess Expressions to walk down the properties and I found that using PropertyExpressions worked without a problem for the simple tests I have. Below is an update that is now working</p> <pre><code>public class MicroRuleEngine { public bool PassesRules&lt;T&gt;(List&lt;Rule&gt; rules, T toInspect) { return this.CompileRules&lt;T&gt;(rules).Invoke(toInspect); } public Func&lt;T, bool&gt; CompileRule&lt;T&gt;(Rule r) { var paramUser = Expression.Parameter(typeof(T)); Expression expr = BuildExpr&lt;T&gt;(r, paramUser); return Expression.Lambda&lt;Func&lt;T, bool&gt;&gt;(expr, paramUser).Compile(); } public Func&lt;T, bool&gt; CompileRules&lt;T&gt;(IList&lt;Rule&gt; rules) { var paramUser = Expression.Parameter(typeof(T)); List&lt;Expression&gt; expressions = new List&lt;Expression&gt;(); foreach (var r in rules) { expressions.Add(BuildExpr&lt;T&gt;(r, paramUser)); } var expr = AndExpressions(expressions); return Expression.Lambda&lt;Func&lt;T, bool&gt;&gt;(expr, paramUser).Compile(); } Expression AndExpressions(IList&lt;Expression&gt; expressions) { if(expressions.Count == 1) return expressions[0]; Expression exp = Expression.And(expressions[0], expressions[1]); for(int i = 2; expressions.Count &gt; i; i++) { exp = Expression.And(exp, expressions[i]); } return exp; } Expression BuildExpr&lt;T&gt;(Rule r, ParameterExpression param) { Expression propExpression; Type propType; ExpressionType tBinary; if (r.MemberName.Contains('.')) { String[] childProperties = r.MemberName.Split('.'); var property = typeof(T).GetProperty(childProperties[0]); var paramExp = Expression.Parameter(typeof(T), "SomeObject"); propExpression = Expression.PropertyOrField(param, childProperties[0]); for (int i = 1; i &lt; childProperties.Length; i++) { property = property.PropertyType.GetProperty(childProperties[i]); propExpression = Expression.PropertyOrField(propExpression, childProperties[i]); } propType = propExpression.Type; } else { propExpression = Expression.PropertyOrField(param, r.MemberName); propType = propExpression.Type; } // is the operator a known .NET operator? if (ExpressionType.TryParse(r.Operator, out tBinary)) { var right = Expression.Constant(Convert.ChangeType(r.TargetValue, propType)); // use a binary operation, e.g. 'Equal' -&gt; 'u.Age == 15' return Expression.MakeBinary(tBinary, propExpression, right); } else { var method = propType.GetMethod(r.Operator); var tParam = method.GetParameters()[0].ParameterType; var right = Expression.Constant(Convert.ChangeType(r.TargetValue, tParam)); // use a method call, e.g. 'Contains' -&gt; 'u.Tags.Contains(some_tag)' return Expression.Call(propExpression, method, right); } } } public class Rule { public string MemberName { get; set; } public string Operator { get; set; } public string TargetValue { get; set; } } </code></pre>
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