IDTSSequence.PrecedenceConstraints 属性

定义

命名空间:

Microsoft.SqlServer.Dts.Runtime

程序集:

Microsoft.SqlServer.ManagedDTS.dll

返回 PrecedenceConstraint 与容器相关的一组对象。 此字段是只读的。

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PrecedenceConstraintsPrecedenceConstraint容器对象的集合。

示例

该 Package 类继承 IDTSSequence 并实现一个 PrecedenceConstraints 集合。以下代码示例演示了向包添加两个任务。 PrecedenceConstraint A被添加到PrecedenceConstraints集合中。 任务之间建立的约束会阻止第二个任务在第一个任务完成前运行。

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

优先级约束确定了可执行对象在包中运行的顺序。 优先级约束允许基于前一任务或容器执行结果来控制包中容器和任务的执行。 通过调用Add容器对象的集合方法PrecedenceConstraints，在两个Executable对象之间建立优先级约束。 在两个可执行对象之间创建约束后， Value 该属性被设置为确定执行约束中定义的第二个可执行文件的条件。