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My software needs to have some sort of rules library. Is there anyway I can serialize a single rule?

Why a single rule? Because prior to actual rule engine execution, I'd want to be able to add some specific rules into my RuleSet, and execute that RuleSet through a windows workflow rule engine.

As per the example given here, I know I can serialize a RuleSet?

Here is a brief of how its done:

1. Creating reference to the discount property this.Discount

CodePropertyReferenceExpression discountProperty =  
    new CodePropertyReferenceExpression( 
    new CodeThisReferenceExpression(),  
    "Discount");

2. Creating reference to the orderValue property

CodePropertyReferenceExpression orderValueProperty = 
    new CodePropertyReferenceExpression( 
        new CodeThisReferenceExpression(),  
        "OrderValue");

3. Defining condition on orderValue object

// if this.OrderValue > 500
RuleCondition discountCondition = new RuleExpressionCondition( 
    new CodeBinaryOperatorExpression( 
        orderValueProperty, 
        CodeBinaryOperatorType.GreaterThan, 
        new CodePrimitiveExpression(500)));

4. Defining the rule action

// Create an action that sets the property Discount to 5% 
RuleStatementAction setDiscountAction = new RuleStatementAction( 
    new CodeAssignStatement(discountProperty,  
        new CodePrimitiveExpression(5)));

5. Creating the RuleSet

Rule discountRule = new Rule("CalculateDiscount"); 
discountRule.Condition = discountCondition; 
discountRule.ThenActions.Add(setDiscountAction); 
ruleSet = new RuleSet("DiscountRuleSet"); 
ruleSet.Rules.Add(discountRule);

6. Seralizing the ruleset

RuleDefinitions ruleDefinitions = new RuleDefinitions(); 
ruleDefinitions.RuleSets.Add(ruleSet); 
WorkflowMarkupSerializer serializer = new WorkflowMarkupSerializer(); 
XmlTextWriter writer = new XmlTextWriter("MyRules.rules", System.Text.Encoding.Unicode); 
serializer.Serialize(writer, ruleDefinitions); 
writer.Close();

7. Executing the ruleset

RuleEngine engine = new RuleEngine(ruleSet, typeof(Shopping));  
// execute the rule on a shopping object where OrderValue = 100 
// expect rule action to be not fired 
Shopping shoppingUnder500 = new Shopping(100); 
engine.Execute(shoppingUnder500); 
Console.WriteLine("shoppingUnder500 - Discount evaluated: " + shoppingUnder500.Discount);

You can get a full example at the link mentioned in the beginning. Pt 6 describes how you can persist a rule set. But I want to know if we can serialize a rule, which is nothing but a codedom condition expression & a set of statements (actions) (again represented by codedom).

Or what is a better way to store a single rule somewhere?

deostroll
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  • (wf4 doesn't have rules) –  Oct 08 '13 at 13:36
  • @Will isn't it built-in to the WWF framework? I think it comes shipped since .net 4.0 & .net 3.5... //fingers crossed// – deostroll Oct 09 '13 at 05:12
  • Noooope. And yuuup. RuleEngine and associated classes were part of the original WF that came out with 3. They're usually found under `System.Workflow.*`. But, [as you can see here](http://msdn.microsoft.com/en-us/library/system.workflow.activities.aspx) the original WF is considered **obsolete**. Not sure how much longer the assemblies will be shipped. At least the rule system types appear not to be marked obsolete. Who knows, no guarantees. WF4 doesn't use any rule engine. Not even sure what part the rule engine played, so I can't say if there is anything analogous now. –  Oct 09 '13 at 13:23

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