IRuleExpression Antarmuka

Definisi

Ruang nama:

System.Workflow.Activities.Rules

Rakitan:

System.Workflow.Activities.dll

Mewakili kelas dasar tempat penulis ekspresi kustom harus berasal untuk menulis ekspresi kustom.

public interface class IRuleExpression

public interface IRuleExpression

type IRuleExpression = interface

Public Interface IRuleExpression

Contoh

Kode berikut membuat ekspresi yang dapat digunakan dalam kondisi deklaratif dan seperangkat aturan. Ekspresi diberi nama TwoOfThree, dan mengambil 3 parameter, yang semuanya harus dievaluasi ke Booleans. Ekspresi ini mengembalikan true jika 2 dari 3 ekspresi mengembalikan true.

Untuk menggunakan kode ini, tambahkan ke proyek Pustaka Kelas dan referensikan pustaka dari proyek alur kerja Anda.

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

namespace TwoOfThreeRuleExpression  
{  
    public class TwoOfThree : CodeExpression, IRuleExpression  
    {  
        CodeExpression expression1, expression2, expression3;  

        public CodeExpression First  
        {  
            get { return expression1; }  
            set { expression1 = value; }  
        }  

        public CodeExpression Second  
        {  
            get { return expression2; }  
            set { expression2 = value; }  
        }  

        public CodeExpression Third  
        {  
            get { return expression3; }  
            set { expression3 = value; }  
        }  

        public TwoOfThree()  
        {  
            // constructor required for deserialization  
        }  

        public TwoOfThree(CodeExpression first, CodeExpression second, CodeExpression third)  
        {  
            // constructor required by parser  
            expression1 = first;  
            expression2 = second;  
            expression3 = third;  
        }  

        public void AnalyzeUsage(RuleAnalysis analysis, bool isRead, bool isWritten, RulePathQualifier qualifier)  
        {  
            // check what the 3 expressions use  
            RuleExpressionWalker.AnalyzeUsage(analysis, expression1, true, false, null);  
            RuleExpressionWalker.AnalyzeUsage(analysis, expression2, true, false, null);  
            RuleExpressionWalker.AnalyzeUsage(analysis, expression3, true, false, null);  
        }  

        public CodeExpression Clone()  
        {  
            TwoOfThree result = new TwoOfThree();  
            result.expression1 = RuleExpressionWalker.Clone(expression1);  
            result.expression2 = RuleExpressionWalker.Clone(expression2);  
            result.expression3 = RuleExpressionWalker.Clone(expression3);  
            return result;  
        }  

        public void Decompile(StringBuilder stringBuilder, CodeExpression parentExpression)  
        {  
            // what should be displayed by the parser  
            stringBuilder.Append("TwoOfThree(");  
            RuleExpressionWalker.Decompile(stringBuilder, expression1, this);  
            stringBuilder.Append(", ");  
            RuleExpressionWalker.Decompile(stringBuilder, expression2, this);  
            stringBuilder.Append(", ");  
            RuleExpressionWalker.Decompile(stringBuilder, expression3, this);  
            stringBuilder.Append(")");  
        }  

        static RuleLiteralResult resultTrue = new RuleLiteralResult(true);  
        static RuleLiteralResult resultFalse = new RuleLiteralResult(false);  

        public RuleExpressionResult Evaluate(RuleExecution execution)  
        {  
            // start by doing the first 2 expressions  
            RuleExpressionResult r1 = RuleExpressionWalker.Evaluate(execution, expression1);  
            RuleExpressionResult r2 = RuleExpressionWalker.Evaluate(execution, expression2);  
            bool b1 = (bool)r1.Value;  
            bool b2 = (bool)r2.Value;  
            if (b1 && b2)  
            {  
                // both are true, so result is true  
                return resultTrue;  
            }  
            else if (b1 || b2)  
            {  
                // only one of the first 2 is true, evaluate the third to determine result  
                return RuleExpressionWalker.Evaluate(execution, expression3);  
            }  
            else  
                // both e1 and e2 are false, so skip e3 and return false;  
                return resultFalse;  
        }  

        public bool Match(CodeExpression expression)  
        {  
            TwoOfThree other = expression as TwoOfThree;  
            return (other != null) &&  
                RuleExpressionWalker.Match(expression1, other.expression1) &&  
                RuleExpressionWalker.Match(expression2, other.expression2) &&  
                RuleExpressionWalker.Match(expression3, other.expression3);  
        }  

        public RuleExpressionInfo Validate(RuleValidation validation, bool isWritten)  
        {  
            ValidateExpression(validation, expression1, "First");  
            ValidateExpression(validation, expression2, "Second");  
            ValidateExpression(validation, expression3, "Third");  
            return new RuleExpressionInfo(typeof(bool));  
        }  

        private void ValidateExpression(RuleValidation validation, CodeExpression expression, string propertyName)  
        {  
            ValidationError error;  
            if (expression == null)  
            {  
                error = new ValidationError(propertyName + " cannot be null", 123);  
                validation.Errors.Add(error);  
            }  
            else  
            {  
                RuleExpressionInfo result = RuleExpressionWalker.Validate(validation, expression, false);  
                if ((result == null) || (result.ExpressionType != typeof(bool)))  
                {  
                    error = new ValidationError(propertyName + " must return boolean result", 123);  
                    validation.Errors.Add(error);  
                }  
            }  
        }  
    }  
}  

Metode

Nama	Deskripsi
AnalyzeUsage(RuleAnalysis, Boolean, Boolean, RulePathQualifier)	Saat ditimpa dalam kelas turunan, melaporkan bagaimana objek menggunakan bidang dan properti dalam jenis konteks.
Clone()	Ketika ditimpa di kelas turunan, membuat salinan mendalam dari saat ini CodeExpression.
Decompile(StringBuilder, CodeExpression)	Saat ditimpa dalam kelas turunan, dekombinasikan ekspresi kustom ke dalam formulir string.
Evaluate(RuleExecution)	Saat ditimpa di kelas turunan, mengevaluasi ekspresi kustom.
Match(CodeExpression)	Membandingkan ekspresi saat ini dengan ekspresi lain untuk menentukan apakah ekspresi tersebut sama.
Validate(RuleValidation, Boolean)	Saat ditimpa dalam kelas turunan, verifikasi bahwa ekspresi dikonfigurasi dengan benar dan tidak memiliki kesalahan.