Walkthrough: Executing the Policy Programmatically

Article
02/02/2021

This walkthrough provides step-by-step procedures for invoking the policy you created in the Walkthrough: Creating a Simple Business Policy walkthrough from a console application programmatically.

Prerequisites

You must complete the Walkthrough: Creating a Simple Business Policy walkthrough before you perform this walkthrough.

Overview of This Walkthrough

This walkthrough contains two procedures, as described in the following table.

Procedure title	Procedure description
To invoke the ProcessPurchaseOrder policy by using the Policy.Execute method	Provides step-by-step instructions for invoking a policy by using the Policy.Execute method.
To invoke the ProcessPurchaseOrder policy by using the RuleEngine.Execute method	Provides step-by-step instructions for invoking a policy by using the RuleEngine.Execute method.

To invoke the ProcessPurchaseOrder policy by using the Policy.Execute method

Start Microsoft Visual Studio.
In Visual Studio, on the File menu, point to New, and then click Project.

In the New Project dialog box, do the following:

Use this	To do this
Project types	Click Visual C#.
Templates	Click Console Application.
Name	Type ConsoleClient.
Location	Specify a folder where you want to save the project files.
Solution Name	Type ConsoleClientSol.
Create directory for solution	Select this check box to create a directory for the solution files.

Click OK. The ConsoleClient project should appear in Solution Explorer. If you do not see Solution Explorer, click Solution Explorer on the View menu.
In Solution Explorer, right-click References, and then click Add Reference.
Click Browse, browse to the \Program Files\Common Files\Microsoft BizTalk, and then double-click Microsoft.RuleEngine.dll.

Add the following lines to the top of the Program.cs file after the existing using statements:

//To use the XmlDocument class  
using System.Xml;  
//To use the TypedXmlDocument and Policy classes  
using Microsoft.RuleEngine;

Add the following code to the Main function to create a TypedXmlDocument object based on the XML document:

XmlDocument doc = new XmlDocument();  
//Loading the XML from SamplePO.xml file.  
//Change the directory as needed  
doc.Load(@"C:\BRE-Walkthroughs\SamplePO.xml");  
TypedXmlDocument txd = new TypedXmlDocument("RuleTest.PO", doc);

Add the following code to the Main function to execute the policy:

//Create a policy object based on the name, ProcessPurchaseOrder  
Policy policy = new Policy("ProcessPurchaseOrder");  
//Execute the policy by invoking Policy.Execute method and   
//by passing the typed xml document as a fact.   
policy.Execute(txd);

Print the output XML to confirm that the value of the Status field is set to Approved. Note that unlike the Business Rule Composer, invoking the Policy.Execute method does not change the original document.
```
//Print the output document  
Console.WriteLine(txd.Document.OuterXml);   
```
On the Build menu, click Build ConsoleClient.
Press CTRL+F5 to execute the application. Confirm that the value of the Status field is set to Approved.

To invoke the ProcessPurchaseOrder policy by using the RuleEngine.Execute method

In Solution Explorer, right-click References, and then click Add Reference.
Click Browse, browse to \Program Files\Common Files\Microsoft BizTalk, and then double-click Microsoft.BizTalk.RuleEngineExtensions.dll.

Comment out the following lines in the Program.cs file:

//Create a policy object based on the name, ProcessPurchaseOrder  
Policy policy = new Policy("ProcessPurchaseOrder");  
//Execute the policy by invoking Policy.Execute method and   
//by passing the typed xml document as a fact.   
policy.Execute(txd);

Add the following code after the commented-out code to get access to the Rule Engine database:

//Get access to the SQL rule store   
Microsoft.BizTalk.RuleEngineExtensions.RuleSetDeploymentDriver dd;  
dd = new Microsoft.BizTalk.RuleEngineExtensions.RuleSetDeploymentDriver();  
SqlRuleStore sqlRuleStore = (SqlRuleStore)dd.GetRuleStore();

Add the following code to get access to RuleSetInfoCollection for the ProcessPurchaseOrder policy:

//Get access to RuleSetInfoCollection for the   
//ProcessPurchaseOrder policy  
RuleSetInfoCollection rsic = sqlRuleStore.GetRuleSets("ProcessPurchaseOrder", RuleStore.Filter.All);

Add the following code to create a RuleSet object based on the rule set information for the ProcessPurchaseOrder policy:

//Create a RuleSet object based on the rule set information   
//for the ProcessPurchaseOrder policy  
RuleSet rs = sqlRuleStore.GetRuleSet(rsic[0]);

Add the following code to create the RuleEngine object:

//Create the RuleEngine object  
Microsoft.RuleEngine.RuleEngine engine = new Microsoft.RuleEngine.RuleEngine(rs);

Add the following code to assert the TypedXmlDocument object into the working memory of the rule engine:

//Assert the TypedXmlDocument object into working memory  
//of the rule engine  
engine.Assert(txd);

Now add the code to execute the policy by using the RuleEngine.Execute method:

//Execute the policy by invoking RuleEngine.Execute method  
engine.Execute();

Make sure that the Console.WriteLine statement is the last statement in the Main function.
On the Build menu, click Build ConsoleClient.
Press CTRL+F5 to execute the application. Confirm that the value of the Status field is set to Approved.

Comments

Complete code for the Main function to execute the ProcessPurchaseOrder policy by using the Policy.Execute method is as follows:

static void Main(string[] args)  
{  
XmlDocument doc = new XmlDocument();  
doc.Load(@"C:\BRE-Walkthroughs\SamplePO.xml");  
TypedXmlDocument txd = new TypedXmlDocument("RuleTest.PO", doc);  
Policy policy = new Policy("ProcessPurchaseOrder");  
policy.Execute(txd);  
Console.WriteLine(txd.Document.OuterXml);   
}

Complete code for executing the ProcessPurchaseOrder policy by using the RuleEngine.Execute method is as follows:

static void Main(string[] args)  
{  
XmlDocument doc = new XmlDocument();  
doc.Load(@"C:\BRE-Walkthroughs\SamplePO.xml");  
TypedXmlDocument txd = new TypedXmlDocument("RuleTest.PO", doc);  
Microsoft.BizTalk.RuleEngineExtensions.RuleSetDeploymentDriver dd;  
dd = new Microsoft.BizTalk.RuleEngineExtensions.RuleSetDeploymentDriver();  
SqlRuleStore sqlRuleStore = (SqlRuleStore)dd.GetRuleStore();  
RuleSetInfoCollection rsic = sqlRuleStore.GetRuleSets("ProcessPurchaseOrder", RuleStore.Filter.All);  
RuleSet rs = sqlRuleStore.GetRuleSet(rsic[0]);  
Microsoft.RuleEngine.RuleEngine engine = new Microsoft.RuleEngine.RuleEngine(rs);  
engine.Assert(txd);  
engine.Execute();  
Console.WriteLine(txd.Document.OuterXml);   
}

You may want to add a Console.ReadLine() statement at the end of the Main function so that the application waits for you to terminate the application.
In this walkthrough, the client submits only one fact to the ProcessPurchaseOrder policy. If the client needs to submit more than one fact to a policy, it needs to create an array of facts and use the overloaded Execute method that takes an array as a parameter. The following sample code shows how to do that:
```
Policy policy = new Policy("PolicyName");  
object[] facts = new object[2];  
facts[0] = txd;  
facts[1] = new MyClass();  
policy.Execute(facts);  
policy.Dispose();  
```
The first parameter to the TypedXmlDocument constructor in the code is the name of the type you used to build the policy.
The Policy.Execute method is basically a wrapper around the RuleEngine.Execute method. Therefore, using the Policy.Execute method is the easiest way of invoking a policy, as you have seen in this walkthrough.
For more control over the execution of the policy, you may want to use the RuleEngine.Execute method instead of using Policy.Execute. For example, you can halt the engine temporarily by using the Halt function, and then resume it by using the Execute function. For more information, see Halt.