IDTSSequence.PrecedenceConstraints 属性

定义

命名空间:

Microsoft.SqlServer.Dts.Runtime

程序集:

Microsoft.SqlServer.ManagedDTS.dll

返回与容器关联的 PrecedenceConstraint 对象的集合。 此字段为只读。

public:
 property Microsoft::SqlServer::Dts::Runtime::PrecedenceConstraints ^ PrecedenceConstraints { Microsoft::SqlServer::Dts::Runtime::PrecedenceConstraints ^ get(); };

public Microsoft.SqlServer.Dts.Runtime.PrecedenceConstraints PrecedenceConstraints { get; }

member this.PrecedenceConstraints : Microsoft.SqlServer.Dts.Runtime.PrecedenceConstraints

Public ReadOnly Property PrecedenceConstraints As PrecedenceConstraints

属性值

PrecedenceConstraints

包含 PrecedenceConstraints 容器对象的集合 PrecedenceConstraint 。

示例

该 Package 类继承并 IDTSSequence 实现集合：下面的代码示例演示如何将两个 PrecedenceConstraints 任务添加到包中。 A PrecedenceConstraint 将添加到 PrecedenceConstraints 集合中。 在任务之间创建的约束可防止第二个任务运行，直到第一个任务完成。

using System;  
using System.Collections.Generic;  
using System.Text;  
using Microsoft.SqlServer.Dts.Runtime;  
using Microsoft.SqlServer.Dts.Pipeline.Wrapper;  
using Microsoft.SqlServer.Dts.Tasks.FileSystemTask;  

namespace DataFlow_Conceptual  
{  
    class Program  
    {  
        static void Main(string[] args)  
        {  
            Package p = new Package();  
            // Add a File System task.  
            Executable eFileTask1 = p.Executables.Add("STOCK:FileSystemTask");  
            TaskHost thFileHost1 = eFileTask1 as TaskHost;  

            // Add a second File System task.  
            Executable eFileTask2 = p.Executables.Add("STOCK:FileSystemTask");  
            TaskHost thFileHost2 = eFileTask2 as TaskHost;  

            // Put a precedence constraint between the tasks.  
            // Set the constraint to be that thFileTask2 cannot run  
            // until thFileTask1 completes.  
            PrecedenceConstraint pcFileTasks = p.PrecedenceConstraints.Add((Executable)thFileHost1, (Executable) thFileHost2);  
            pcFileTasks.Value = DTSExecResult.Completion;  
        }  
    }  
}  

Imports System  
Imports System.Collections.Generic  
Imports System.Text  
Imports Microsoft.SqlServer.Dts.Runtime  
Imports Microsoft.SqlServer.Dts.Pipeline.Wrapper  
Imports Microsoft.SqlServer.Dts.Tasks.FileSystemTask  

Namespace DataFlow_Conceptual  
    Class Program  
        Shared  Sub Main(ByVal args() As String)  
            Dim p As Package =  New Package()   
            ' Add a File System task.  
            Dim eFileTask1 As Executable =  p.Executables.Add("STOCK:FileSystemTask")   
            Dim thFileHost1 As TaskHost =  eFileTask1 as TaskHost   

            ' Add a second File System task.  
            Dim eFileTask2 As Executable =  p.Executables.Add("STOCK:FileSystemTask")   
            Dim thFileHost2 As TaskHost =  eFileTask2 as TaskHost   

            ' Put a precedence constraint between the tasks.  
            ' Set the constraint to be that thFileTask2 cannot run  
            ' until thFileTask1 completes.  
            Dim pcFileTasks As PrecedenceConstraint =  p.PrecedenceConstraints.Add(CType(thFileHost1,CType(thFileHost2, Executable, Executable)))   
            pcFileTasks.Value = DTSExecResult.Completion  
        End Sub  
    End Class  
End Namespace  

注解

优先约束建立可执行对象在包中运行的顺序。 优先约束允许控制包中的容器和任务的执行，具体取决于上一个任务或容器的执行结果。 通过在容器对象上调用Add集合的方法PrecedenceConstraints，在两Executable个对象之间建立优先约束。 在两个可执行对象之间创建约束后，该 Value 属性设置为建立用于执行约束中定义的第二个可执行文件的条件。