PrecedenceConstraints.GetEnumerator Method

Articolo
12/15/2008

Returns an enumerator for use in iterating over the PrecedenceConstraints collection.

Spazio dei nomi: Microsoft.SqlServer.Dts.Runtime
Assembly : Microsoft.SqlServer.ManagedDTS (in microsoft.sqlserver.manageddts.dll)

Sintassi

'Dichiarazione
Public Function GetEnumerator As PrecedenceConstraintEnumerator

public PrecedenceConstraintEnumerator GetEnumerator ()

public:
PrecedenceConstraintEnumerator^ GetEnumerator ()

public PrecedenceConstraintEnumerator GetEnumerator ()

public function GetEnumerator () : PrecedenceConstraintEnumerator

Valore restituito

A PrecedenceConstraintEnumerator.

Osservazioni

If the call to the Contains method returns true, you can access the specified element in the collection by using the syntax PrecedenceConstraints[index]. However, if the Contains method returns false, this property throws an exception. In C#, this property is the indexer for the PrecedenceConstraints class.

Esempio

The following code example creates two precedence constraints. It then uses Contains to verify the existence of a specific constraint, counts the number of constraints before and after the use of the Remove method, and shows how to use the GetEnumerator to iterate over the collection, using the Item syntax of pConsts[i].ID to return the ID of the constraint.

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

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 constraint between eFileTask1 and eFileTask2.
            // Set the constraint to be that eFileTask2 cannot run 
            // until eFileTask1 completes.
            PrecedenceConstraint pcFileTasks = pkg.PrecedenceConstraints.Add(eFileTask1, eFileTask2);
            pcFileTasks.Name = "constraint between File System Tasks";

            // Add another precedence constraint. 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);
            pcFileTasks.Name = "constraint between File System and Bulk Insert Tasks";

            // Obtain the precedence constraint collection.
            PrecedenceConstraints pConsts = pkg.PrecedenceConstraints;
            Boolean containsConstraint = pkg.PrecedenceConstraints.Contains("constraint between File System and Bulk Insert Tasks");
            Console.WriteLine("Contains the constraint between File System and Bulk Insert Tasks? {0}", containsConstraint);
            
            // Create the enumerator.
            PrecedenceConstraintEnumerator myEnumerator = pConsts.GetEnumerator();
            // Iterate over the collection, and remove the Bulk Insert task.
            int i = 0;
            while ((myEnumerator.MoveNext()) && (myEnumerator.Current != null))
            {
                Console.WriteLine("ID {0}", pConsts[i].ID);
            }

            Console.WriteLine("Number of constraints {0}", pConsts.Count);
            // Remove the second contstraint.
            pConsts.Remove(1);
            // Verify that one has been removed.
            Console.WriteLine("Number of constraints {0}", pConsts.Count);

            Console.WriteLine();
        }
    }
}

Imports System
Imports System.Collections.Generic
Imports System.Text
Imports Microsoft.SqlServer.Dts.Runtime
Imports Microsoft.SqlServer.Dts.Tasks.FileSystemTask
Imports Microsoft.SqlServer.Dts.Tasks.BulkInsertTask
 
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 constraint 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) 
            pcFileTasks.Name = "constraint between File System Tasks"
 
            ' Add another precedence constraint. 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) 
            pcFileTasks.Name = "constraint between File System and Bulk Insert Tasks"
 
            ' Obtain the precedence constraint collection.
            Dim pConsts As PrecedenceConstraints =  pkg.PrecedenceConstraints 
            Dim containsConstraint As Boolean =  pkg.PrecedenceConstraints.Contains("constraint between File System and Bulk Insert Tasks") 
            Console.WriteLine("Contains the constraint between File System and Bulk Insert Tasks? {0}", containsConstraint)
 
            ' Create the enumerator.
            Dim myEnumerator As PrecedenceConstraintEnumerator =  pConsts.GetEnumerator() 
            ' Iterate over the collection, and remove the Bulk Insert task.
            Dim i As Integer =  0 
            While (myEnumerator.MoveNext()) &&(myEnumerator.Current <> Nothing)
                Console.WriteLine("ID {0}", pConsts(i).ID)
            End While
 
            Console.WriteLine("Number of constraints {0}", pConsts.Count)
            ' Remove the second contstraint.
            pConsts.Remove(1)
            ' Verify that one has been removed.
            Console.WriteLine("Number of constraints {0}", pConsts.Count)
 
            Console.WriteLine()
        End Sub
    End Class
End Namespace

Sample Output:

Contains the constraint between File System and Bulk Insert Tasks? True

ID {BA42AF32-3AC1-4CB6-85A2-289760ADBFA4}

Number of constraints 2

Number of constraints 1

Thread Safety

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

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