PrecedenceConstraint.Expression 属性

参考

定义

命名空间:: Microsoft.SqlServer.Dts.Runtime

程序集:: Microsoft.SqlServer.ManagedDTS.dll

重要

一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。

如果 EvalOp 设置为 Expression、ExpressionAndConstraint 或 ExpressionOrConstraint，获取或设置优先约束使用的表达式。

public:
 property System::String ^ Expression { System::String ^ get(); void set(System::String ^ value); };

[Microsoft.SqlServer.Dts.Runtime.Localization.LocalizablePropertyDescription(typeof(Microsoft.SqlServer.Dts.Runtime.Localized), "PCExpressionDesc")]
public string Expression { get; set; }

[<Microsoft.SqlServer.Dts.Runtime.Localization.LocalizablePropertyDescription(typeof(Microsoft.SqlServer.Dts.Runtime.Localized), "PCExpressionDesc")>]
member this.Expression : string with get, set

Public Property Expression As String

属性值

String

包含优先约束使用的表达式的字符串。

属性: LocalizablePropertyDescriptionAttribute

示例

下面的代码示例创建三个任务，并使用优先约束连接它们。然后，该示例循环访问包集合中 PrecedenceConstraints 的约束，并打印有关每个约束的信息。

using System;  
using System.Collections.Generic;  
using System.Text;  
using Microsoft.SqlServer.Dts.Runtime;  

namespace PrecedenceConst  
{  
    class Program  
    {  
        static void Main(string[] args)  
        {  
            Package pkg = new Package();  
            // Add a File System task.  
            Executable eFileTask1 = pkg.Executables.Add("STOCK:FileSystemTask");  
            TaskHost thFileTask1 = eFileTask1 as TaskHost;  

            // Add a second File System task.  
            Executable eFileTask2 = pkg.Executables.Add("STOCK:FileSystemTask");  
            TaskHost thFileTask2 = eFileTask2 as TaskHost;  

            // Add a Bulk Insert task.  
            Executable eBulkInsert = pkg.Executables.Add("STOCK:BulkInsertTask");  
            TaskHost thBulkInsert = eBulkInsert as TaskHost;  

            // Add a precedence contraint between eFileTask1 and eFileTask2.  
            // Set the constraint to be that eFileTask2 cannot run   
            // until eFileTask1 completes.  
            PrecedenceConstraint pcFileTasks = pkg.PrecedenceConstraints.Add(eFileTask1, eFileTask2);  

            // Add another precedence contraint. Add it between eFileTask2 and BulkInsert.  
            // Again, set the constraint to be that BulkInsert cannot run   
            // until eFileTask2 completes.  
            PrecedenceConstraint pcFiletoBulk = pkg.PrecedenceConstraints.Add(eFileTask2, eBulkInsert);  

            // Obtain the precedence constraint collection, and display properties.  
            // Some properties are read/write and have not been set.  
            PrecedenceConstraints pConsts = pkg.PrecedenceConstraints;  
            foreach (PrecedenceConstraint pc in pConsts)  
            {  
                Console.WriteLine("Constrained container  {0}", pc.ConstrainedExecutable);  
                Console.WriteLine("Creation Name          {0}", pc.CreationName);  
                Console.WriteLine("Description            {0}", pc.Description);  
                Console.WriteLine("Evaluation operation   {0}", pc.EvalOp);  
                Console.WriteLine("Evaluates true         {0}", pc.EvaluatesTrue);  
                Console.WriteLine("Expression             {0}", pc.Expression);  
                Console.WriteLine("ID                     {0}", pc.ID);  
                Console.WriteLine("LogicalAnd             {0}", pc.LogicalAnd);  
                Console.WriteLine("Name                   {0}", pc.Name);  
                Console.WriteLine("Precedence Executable  {0}", pc.PrecedenceExecutable);  
                Console.WriteLine("Value                  {0}", pc.Value);  
                Console.WriteLine("-----------------------------------");  
            }  
        }  
    }  
}

Imports System  
Imports System.Collections.Generic  
Imports System.Text  
Imports Microsoft.SqlServer.Dts.Runtime  

Namespace PrecedenceConst  
    Class Program  
        Shared  Sub Main(ByVal args() As String)  
            Dim pkg As Package =  New Package()   
            ' Add a File System task.  
            Dim eFileTask1 As Executable =  pkg.Executables.Add("STOCK:FileSystemTask")   
            Dim thFileTask1 As TaskHost =  eFileTask1 as TaskHost   

            ' Add a second File System task.  
            Dim eFileTask2 As Executable =  pkg.Executables.Add("STOCK:FileSystemTask")   
            Dim thFileTask2 As TaskHost =  eFileTask2 as TaskHost   

            ' Add a Bulk Insert task.  
            Dim eBulkInsert As Executable =  pkg.Executables.Add("STOCK:BulkInsertTask")   
            Dim thBulkInsert As TaskHost =  eBulkInsert as TaskHost   

            ' Add a precedence contraint between eFileTask1 and eFileTask2.  
            ' Set the constraint to be that eFileTask2 cannot run   
            ' until eFileTask1 completes.  
            Dim pcFileTasks As PrecedenceConstraint =  pkg.PrecedenceConstraints.Add(eFileTask1,eFileTask2)   

            ' Add another precedence contraint. Add it between eFileTask2 and BulkInsert.  
            ' Again, set the constraint to be that BulkInsert cannot run   
            ' until eFileTask2 completes.  
            Dim pcFiletoBulk As PrecedenceConstraint =  pkg.PrecedenceConstraints.Add(eFileTask2,eBulkInsert)   

            ' Obtain the precedence constraint collection, and display properties.  
            ' Some properties are read/write and have not been set.  
            Dim pConsts As PrecedenceConstraints =  pkg.PrecedenceConstraints   
            Dim pc As PrecedenceConstraint  
            For Each pc In pConsts  
                Console.WriteLine("Constrained container  {0}", pc.ConstrainedExecutable)  
                Console.WriteLine("Creation Name          {0}", pc.CreationName)  
                Console.WriteLine("Description            {0}", pc.Description)  
                Console.WriteLine("Evaluation operation   {0}", pc.EvalOp)  
                Console.WriteLine("Evaluates true         {0}", pc.EvaluatesTrue)  
                Console.WriteLine("Expression             {0}", pc.Expression)  
                Console.WriteLine("ID                     {0}", pc.ID)  
                Console.WriteLine("LogicalAnd             {0}", pc.LogicalAnd)  
                Console.WriteLine("Name                   {0}", pc.Name)  
                Console.WriteLine("Precedence Executable  {0}", pc.PrecedenceExecutable)  
                Console.WriteLine("Value                  {0}", pc.Value)  
                Console.WriteLine("-----------------------------------")  
            Next  
        End Sub  
    End Class  
End Namespace

示例输出：

受约束容器 Microsoft.SqlServer.Dts.Runtime.TaskHost

创建名称

说明

评估操作约束

计算 true True

Expression

ID {BA20A288-545D-4E48-864A-E6AF6C3B9AEE}

LogicalAnd True

名称 {BA20A288-545D-4E48-864A-E6AF6C3B9AEE}

优先级可执行文件 Microsoft.SqlServer.Dts.Runtime.TaskHost

值成功

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