evaluationenginetipsandtricks.html

---
layout: documentation 
title: EvaluationEngine 
teaser: Decouple business logic from control flow
navigation:
   - name: Overview
     link: evaluationengine.html
   - name: Tutorial
     link: evaluationenginetutorial.html	
   - name: Modules
     link: evaluationenginemodules.html
   - name: Hierarchical Evaluation Engines
     link: evaluationenginehierarchies.html
   - name: Aggregators
     link: evaluationengineaggregators.html
   - name: Expressions
     link: evaluationengineexpressions.html
   - name: Strategies
     link: evaluationenginestrategies.html
   - name: Validation
     link: evaluationenginevalidation.html
   - name: Logging
     link: evaluationenginelogging.html
   - name: Tips and Tricks
     link: evaluationenginetipsandtricks.html
   - name: Specifications
     link: evaluationenginespecifications.html		 
---
<h2>Tips and tricks</h2>

<h3>Use Extension Methods whenever possible</h3>
<p>
Extension methods can make the solution definition much better readable.
Therefore use your custom made extension methods for your strategies, aggregators and questions.
</p>
<p>
Instead of this:
</p>
<script type="syntaxhighlighter" class="brush: csharp"><![CDATA[
evaluationEngine.Solve<HowCoolIsTheEvaluationEngine, string>()
	.With(new AggregatorStrategy<HowCoolIsTheEvaluationEngine, string, Missing>())
	.AggregateWith(new Aggregators.ExpressionAggregator<string, string, Missing>(
	    string.Empty, 
		(aggregate, value) => aggregate + " " + value))
	.ByEvaluating((q, p) => "extremely")
	.ByEvaluating((q, p) => "super")
	.ByEvaluating((q, p) => "fantastic");
]]></script>
<p>
you get this:
</p>
<script type="syntaxhighlighter" class="brush: csharp"><![CDATA[
evaluationEngine.SolveHowCoolIsTheEvaluationEngine()
	.WithAggregatorStrategy()
	.AggregateWithExpressionAggregator(string.Empty, (aggregate, value) => aggregate + " " + value)
	.ByEvaluating((q, p) => "extremely")
	.ByEvaluating((q, p) => "super")
	.ByEvaluating((q, p) => "fantastic");
]]></script>
<p>
These are the extension methods used:
</p>
<script type="syntaxhighlighter" class="brush: csharp"><![CDATA[
public static IDefinitionSyntax<HowCoolIsTheEvaluationEngine, string, Missing, string> 
    SolveHowCoolIsTheEvaluationEngine(this IEvaluationEngine engine)
{
	return engine.Solve<HowCoolIsTheEvaluationEngine, string>();
}

public static IAggregatorSyntax<TQuestion, TAnswer, TParameter, TExpressionResult> 
    WithAggregatorStrategy<TQuestion, TAnswer, TParameter, TExpressionResult>(
        this IDefinitionSyntax<TQuestion, TAnswer, TParameter, TExpressionResult> syntax)
    where TQuestion : IQuestion<TAnswer, TParameter>
{
	return syntax.With(new AggregatorStrategy<TQuestion, TAnswer, TParameter, TExpressionResult>());
}

public static IConstraintSyntax<TQuestion, TAnswer, TParameter, TExpressionResult> 
    AggregateWithExpressionAggregator<TQuestion, TAnswer, TParameter, TExpressionResult>(
        this IAggregatorSyntax<TQuestion, TAnswer, TParameter, TExpressionResult> syntax, 
		TAnswer seed, 
		Expression<Func<TAnswer, TExpressionResult, TAnswer>> aggregateFunc)
    where TQuestion : IQuestion<TAnswer, TParameter>
{
	return syntax.AggregateWith(new Aggregators.ExpressionAggregator<TExpressionResult, TAnswer, TParameter>(seed, aggregateFunc));
}
]]></script>
<p>
Pleae note that the extension methods for aggregator strategy and expression aggregator are already part of Appccelerate.
</p>