Sequence.PrecedenceConstraints Property
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Returns a collection of PrecedenceConstraint objects that describe the precedence constraints that link container-level containers and tasks into an ordered control flow
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.PrecedenceConstraintsPublic ReadOnly Property PrecedenceConstraints As PrecedenceConstraintsProperty Value
A PrecedenceConstraints collection.
Implements
Examples
The following code example creates a Sequence object, and creates three tasks, placing precedence constraints between them. Using the PrecedenceConstraints collection, it iterates over the constraints in the Sequence, printing information about each constraint.
using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.SqlServer.Dts.Runtime;
using Microsoft.SqlServer.Dts.Tasks. FileSystemTask;
namespace Sequence_API
{
class Program
{
static void Main(string[] args)
{
Package package = new Package();
Sequence seq = (Sequence)package.Executables.Add("STOCK:SEQUENCE");
// Add a File System task.
Executable eFileTask1 = seq.Executables.Add("STOCK:FileSystemTask");
TaskHost thFileTask1 = eFileTask1 as TaskHost;
// Add a second File System task.
Executable eFileTask2 = seq.Executables.Add("STOCK:FileSystemTask");
TaskHost thFileTask2 = eFileTask2 as TaskHost;
// Add a Bulk Insert task.
Executable eBulkInsert = seq.Executables.Add("STOCK:BulkInsertTask");
TaskHost thBulkInsert = eBulkInsert as TaskHost;
// Add a precedence contraint between eFileTask1 and eFileTask2.
// Set the constraint to be that eFileTask2 cannot run
// until eFileTask1 completes.
PrecedenceConstraint pcFileTasks = seq.PrecedenceConstraints.Add(eFileTask1, eFileTask2);
// Add another precedence contraint. Add it between eFileTask2 and BulkInsert.
// Again, set the constraint to be that BulkInsert cannot run
// until eFileTask2 completes.
PrecedenceConstraint pcFiletoBulk = seq.PrecedenceConstraints.Add(eFileTask2, eBulkInsert);
// Obtain the precedence constraint collection, and display properties.
// Some properties are read/write and have not been set.
PrecedenceConstraints seqPCs = seq.PrecedenceConstraints;
int numPCs = seqPCs.Count;
Console.WriteLine("Number of precedence constraints in Sequence: {0}", numPCs);
Console.WriteLine("----------------------------------------");
foreach (PrecedenceConstraint pc in seqPCs)
{
Console.WriteLine("Constrained container {0}", pc.ConstrainedExecutable);
Console.WriteLine("Description {0}", pc.Description);
Console.WriteLine("Evaluation operation {0}", pc.EvalOp);
Console.WriteLine("Evaluates true {0}", pc.EvaluatesTrue);
Console.WriteLine("ID {0}", pc.ID);
Console.WriteLine("LogicalAnd {0}", pc.LogicalAnd);
Console.WriteLine("Name {0}", pc.Name);
Console.WriteLine("Precedence Executable {0}", pc.PrecedenceExecutable);
Console.WriteLine("Value {0}", pc.Value);
Console.WriteLine("-----------------------------------");
}
Executables seqExecs = seq.Executables;
int numExecs = seqExecs.Count;
Console.WriteLine("Number of Executables in Sequence: {0}", numExecs);
}
}
}
Imports System
Imports System.Collections.Generic
Imports System.Text
Imports Microsoft.SqlServer.Dts.Runtime
Imports Microsoft.SqlServer.Dts.Tasks. FileSystemTask
Namespace Sequence_API
Class Program
Shared Sub Main(ByVal args() As String)
Dim package As Package = New Package()
Dim seq As Sequence = CType(package.Executables.Add("STOCK:SEQUENCE"), Sequence)
' Add a File System task.
Dim eFileTask1 As Executable = seq.Executables.Add("STOCK:FileSystemTask")
Dim thFileTask1 As TaskHost = eFileTask1 as TaskHost
' Add a second File System task.
Dim eFileTask2 As Executable = seq.Executables.Add("STOCK:FileSystemTask")
Dim thFileTask2 As TaskHost = eFileTask2 as TaskHost
' Add a Bulk Insert task.
Dim eBulkInsert As Executable = seq.Executables.Add("STOCK:BulkInsertTask")
Dim thBulkInsert As TaskHost = eBulkInsert as TaskHost
' Add a precedence contraint between eFileTask1 and eFileTask2.
' Set the constraint to be that eFileTask2 cannot run
' until eFileTask1 completes.
Dim pcFileTasks As PrecedenceConstraint = seq.PrecedenceConstraints.Add(eFileTask1,eFileTask2)
' Add another precedence contraint. Add it between eFileTask2 and BulkInsert.
' Again, set the constraint to be that BulkInsert cannot run
' until eFileTask2 completes.
Dim pcFiletoBulk As PrecedenceConstraint = seq.PrecedenceConstraints.Add(eFileTask2,eBulkInsert)
' Obtain the precedence constraint collection, and display properties.
' Some properties are read/write and have not been set.
Dim seqPCs As PrecedenceConstraints = seq.PrecedenceConstraints
Dim numPCs As Integer = seqPCs.Count
Console.WriteLine("Number of precedence constraints in Sequence: {0}", numPCs)
Console.WriteLine("----------------------------------------")
Dim pc As PrecedenceConstraint
For Each pc In seqPCs
Console.WriteLine("Constrained container {0}", pc.ConstrainedExecutable)
Console.WriteLine("Description {0}", pc.Description)
Console.WriteLine("Evaluation operation {0}", pc.EvalOp)
Console.WriteLine("Evaluates true {0}", pc.EvaluatesTrue)
Console.WriteLine("ID {0}", pc.ID)
Console.WriteLine("LogicalAnd {0}", pc.LogicalAnd)
Console.WriteLine("Name {0}", pc.Name)
Console.WriteLine("Precedence Executable {0}", pc.PrecedenceExecutable)
Console.WriteLine("Value {0}", pc.Value)
Console.WriteLine("-----------------------------------")
Next
Dim seqExecs As Executables = seq.Executables
Dim numExecs As Integer = seqExecs.Count
Console.WriteLine("Number of Executables in Sequence: {0}", numExecs)
End Sub
End Class
End Namespace
Sample Output:
Number of precedence constraints in Sequence: 2
----------------------------------------
Constrained container Microsoft.SqlServer.Dts.Runtime.TaskHost
Description
Evaluation operation Constraint
Evaluates true True
ID {A4F5C0E6-A9A6-470D-9646-7FEAFE3B45AD}
LogicalAnd True
Name {A4F5C0E6-A9A6-470D-9646-7FEAFE3B45AD}
Precedence Executable Microsoft.SqlServer.Dts.Runtime.TaskHost
Value Success
-----------------------------------
Constrained container Microsoft.SqlServer.Dts.Runtime.TaskHost
Description
Evaluation operation Constraint
Evaluates true True
ID {665C52DE-232A-4593-ADF1-7C51949712B8}
LogicalAnd True
Name {665C52DE-232A-4593-ADF1-7C51949712B8}
Precedence Executable Microsoft.SqlServer.Dts.Runtime.TaskHost
Value Success
-----------------------------------
Number of Executables in Sequence: 3
Remarks
Precedence constraints link containers and tasks into an ordered workflow. You can implement precedence constraints between all types of containers and tasks except packages. For more information, see Precedence Constraints.