Artigo
09/28/2010

Classe DtsEnumerator

Defines an abstract base class that implements the IEnumerator methods.

Namespace: Microsoft.SqlServer.Dts.Runtime
Assembly: Microsoft.SqlServer.ManagedDTS (em Microsoft.SqlServer.ManagedDTS.dll)

Sintaxe

'Declaração
Public MustInherit Class DtsEnumerator _
    Implements IEnumerator
'Uso
Dim instance As DtsEnumerator

public abstract class DtsEnumerator : IEnumerator

public ref class DtsEnumerator abstract : IEnumerator

[<AbstractClassAttribute>]
type DtsEnumerator =  
    class
        interface IEnumerator
    end

public abstract class DtsEnumerator implements IEnumerator

Comentários

DtsEnumerator is the base interface for all enumerators. The DtsEnumerator allows only reading of the data in the collection and is not used to modify the underlying collection.

Initially, the enumerator is positioned before the first element in the collection. Reset also brings the enumerator back to this position. At this position, calling Current throws an exception. Therefore, you must call MoveNext to advance the enumerator to the first element of the collection before reading the value of Current.

Current returns the same object until either MoveNext or Reset is called. MoveNext sets Current to the next element.

After the end of the collection is passed, the enumerator is positioned after the last element in the collection, and calling MoveNext returns false. If the last call to MoveNext returned false, calling Current throws an exception. To set Current to the first element of the collection again, you can call Reset followed by MoveNext.

An enumerator remains valid as long as the collection remains unchanged. If changes are made to the collection, such as adding, modifying, or deleting elements, the enumerator is irrecoverably invalidated and the next call to MoveNext or Reset throws an InvalidOperationException. If the collection is modified between MoveNext and Current, Current will return the element that it is set to, even if the enumerator is already invalidated.

The enumerator does not have exclusive access to the collection; therefore, enumerating through a collection is not a thread-safe procedure. Even when a collection is synchronized, other threads could still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can lock the collection during the entire enumeration or catch the exceptions that result from changes made by other threads.

Exemplos

The following code example adds a task to a package then runs the package. The warnings collection is shown by creating a WarningEnumerator, which inherits from this DtsEnumerator class, and displays each warning description.

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

namespace Microsoft.SqlServer.SSIS.Samples
{
    class Program
    {
        static void Main(string[] args)
        {
            Package package = new Package();
            Console.WriteLine("Package warnings count before running: {0}", package.Warnings.Count);

            TaskHost taskH2 = (TaskHost)package.Executables.Add("STOCK:SendMailTask");
            taskH2.FailPackageOnFailure = false;
            taskH2.FailParentOnFailure = false;
            Console.WriteLine("SendMailTask: {0}", taskH2.ID);
 
            // Test that warnings were successfully added to the collection.
            package.MaximumErrorCount = 100;
            package.FailPackageOnFailure = false;
            package.FailParentOnFailure = false;
            package.DelayValidation = true;
            package.Execute();

            Console.WriteLine("Package warnings count after running the package: {0}", package.Warnings.Count);

            // Create the enumerator.
            WarningEnumerator myEnumerator = package.Warnings.GetEnumerator();
            Console.WriteLine("The collection contains the following values:");
            int i = 0;
            while ((myEnumerator.MoveNext()) && (myEnumerator.Current != null))
                Console.WriteLine("[{0}] {1}", i++, myEnumerator.Current.Description);
        }
    }
}

Imports System
Imports System.Collections.Generic
Imports System.Text
Imports Microsoft.SqlServer.Dts.Runtime
Imports Microsoft.SqlServer.Dts.Tasks.ExecuteSQLTask
 
Namespace Microsoft.SqlServer.SSIS.Samples
    Class Program
        Shared  Sub Main(ByVal args() As String)
            Dim package As Package =  New Package() 
            Console.WriteLine("Package warnings count before running: {0}", package.Warnings.Count)
 
            Dim taskH2 As TaskHost = CType(package.Executables.Add("STOCK:SendMailTask"), TaskHost)
            taskH2.FailPackageOnFailure = False
            taskH2.FailParentOnFailure = False
            Console.WriteLine("SendMailTask: {0}", taskH2.ID)
 
            ' Test that warnings were successfully added to the collection.
            package.MaximumErrorCount = 100
            package.FailPackageOnFailure = False
            package.FailParentOnFailure = False
            package.DelayValidation = True
            package.Execute()
 
            Console.WriteLine("Package warnings count after running the package: {0}", package.Warnings.Count)
 
            ' Create the enumerator.
            Dim myEnumerator As WarningEnumerator =  package.Warnings.GetEnumerator() 
            Console.WriteLine("The collection contains the following values:")
            Dim i As Integer =  0 
            While (myEnumerator.MoveNext()) &&(myEnumerator.Current <> Nothing)
                Console.WriteLine("[{0}] {1}",i = Console.WriteLine("[{0}] {1}",i + 1
            End While
        End Sub
    End Class
End Namespace

Sample Output:

Package warnings count before running: 0

SendMailTask: {34CAEFF9-64BF-401D-B646-C88B705DB971}

Package warnings count after running the package: 2

The collection contains the following values:

[0] The address in the From line is not formed correctly. It is missing an @ or it is not valid.

[1] Subject is empty

Hierarquia de herança

Segurança de thread

Quaisquer membros static (Shared no Visual Basic) públicos deste tipo são thread-safe. Não há garantia de que qualquer membro de instância seja thread-safe.

Consulte também

Referência

Membros DtsEnumerator

Namespace Microsoft.SqlServer.Dts.Runtime

Partilhar via