PrecedenceConstraintEnumerator.Current Proprietà

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

public Microsoft.SqlServer.Dts.Runtime.PrecedenceConstraint Current { get; }

member this.Current : Microsoft.SqlServer.Dts.Runtime.PrecedenceConstraint

Public ReadOnly Property Current As PrecedenceConstraint

Valore della proprietà

PrecedenceConstraint

Oggetto PrecedenceConstraint corrente.

Esempio

Nell'esempio di codice seguente vengono creati due vincoli di precedenza. Viene quindi usato Contains per verificare l'esistenza di un vincolo specifico, conta il numero di vincoli prima e dopo l'uso del Remove metodo e mostra come usare l'iterazione GetEnumerator sulla raccolta, usando la Item[] sintassi di pConsts[i].ID per restituire il ID vincolo.

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  

Esempio di output

Contiene il vincolo tra file system e attività di inserimento bulk? Vero

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

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

Numero di vincoli 2

Numero di vincoli 1

Commenti

Dopo aver creato un enumeratore o dopo una chiamata al Reset metodo, il MoveNext metodo deve essere chiamato per avanzare l'enumeratore al primo elemento della raccolta prima che l'enumeratore possa leggere il valore della Current proprietà; in caso contrario, Current non è definito e genera un'eccezione.

Current genera anche un'eccezione se l'ultima chiamata a MoveNext restituita false, che indica la fine della raccolta.

Current non sposta la posizione dell'enumeratore e le chiamate consecutive per Current restituire lo stesso oggetto finché non MoveNext viene chiamato o Reset .

Un enumeratore rimane valido finché la raccolta rimane invariata. Se le modifiche vengono apportate alla raccolta, ad esempio l'aggiunta, la modifica o l'eliminazione di elementi, l'enumeratore viene invalidato e diventa irrecuperabile; quindi, la chiamata successiva a MoveNext o Reset genera un InvalidOperationExceptionoggetto . Se la raccolta viene modificata tra chiamate a MoveNext e Current, Current restituisce l'elemento impostato su, anche se l'enumeratore è stato invalidato.

Si applica a