RuleAction Class

Represents an abstract class that defines an action to be executed if the associated Condition evaluates to true, for ThenActions, or false, for ElseActions. This class must be inherited.

Namespace:  System.Workflow.Activities.Rules
Assembly:  System.Workflow.Activities (in System.Workflow.Activities.dll)

public abstract class RuleAction

RuleStatementAction objects (which can be used as both ThenActions and ElseActions) typically set a variable value on one of the properties of the activity, call a method of the activity, or call static methods on types in referenced assemblies.

RuleAction is the base type that RuleStatementAction, RuleHaltAction, and RuleUpdateAction classes derive from. The uses of these classes is as follows:

  • A RuleStatementAction modifies a property or calls a method.

  • A RuleHaltAction causes the RuleSet to stop executing and returns control to the calling method.

  • A RuleUpdateAction explicitly indicates that a rule is updating a variable. This causes the re-evaluation of any affected rules.

The following code creates an action that can be used in rule sets. The action is named Log, and takes a single parameter, which must evaluate to a string. This action outputs the string to the Console.

To use this code, add it to a Class Library project and reference the library from your workflow project.

using System;
using System.CodeDom;
using System.Collections.Generic;
using System.Text;
using System.Workflow.Activities.Rules;
using System.Workflow.ComponentModel.Compiler;

namespace LogRuleAction
    public class Log : RuleAction
        CodeExpression message;

        public CodeExpression Message
            get { return message; }
            set { message = value; }

        public Log()
            // constructor required for deserialization

        public Log(CodeExpression expression)
            // constructor required by parser
            message = expression;

        public override bool Validate(RuleValidation validator)
            ValidationError error;
            if (message == null)
                error = new ValidationError("Message cannot be null", 123);
                return false;
                RuleExpressionInfo result = RuleExpressionWalker.Validate(validator, message, false);
                if ((result == null) || (result.ExpressionType != typeof(string)))
                    error = new ValidationError("Message must return string result", 123);
                    return false;
            return (validator.Errors.Count == 0);

        public override RuleAction Clone()
            Log result = new Log();
            result.Message = RuleExpressionWalker.Clone(message);
            return result;

        public override void Execute(RuleExecution context)
            RuleExpressionResult result = RuleExpressionWalker.Evaluate(context, message);
            if (result != null)

        public override ICollection<string> GetSideEffects(RuleValidation validation)
            RuleAnalysis analysis = new RuleAnalysis(validation, true);
            if (message != null)
                RuleExpressionWalker.AnalyzeUsage(analysis, message, true, false, null);
            return analysis.GetSymbols();

        public override string ToString()
            // what should be displayed by the parser
            StringBuilder result = new StringBuilder("Log(");
            RuleExpressionWalker.Decompile(result, message, null);
            return result.ToString();

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0
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