Proprietà ForLoop.EvalExpression
Gets or sets the expression that is evaluated on each pass of the loop.
Spazio dei nomi Microsoft.SqlServer.Dts.Runtime
Assembly: Microsoft.SqlServer.ManagedDTS (in Microsoft.SqlServer.ManagedDTS.dll)
Sintassi
'Dichiarazione
Public Property EvalExpression As String
Get
Set
'Utilizzo
Dim instance As ForLoop
Dim value As String
value = instance.EvalExpression
instance.EvalExpression = value
public string EvalExpression { get; set; }
public:
property String^ EvalExpression {
String^ get ();
void set (String^ value);
}
member EvalExpression : string with get, set
function get EvalExpression () : String
function set EvalExpression (value : String)
Valore proprietà
Tipo: System.String
A String that contains the expression used to test whether the loop should stop or continue looping.
Osservazioni
In each iteration of the loop, the ForLoop container evaluates an expression and repeats its workflow until the expression evaluates to false.
Esempi
The following code example creates a ForLoop and sets the three expression properties. The ForLoop also contains two tasks with a precedence constraint.
using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.SqlServer.Dts.Runtime;
using Microsoft.SqlServer.Dts.Tasks.SendMailTask;
using Microsoft.SqlServer.Dts.Tasks.BulkInsertTask;
namespace ForLoopAPI
{
class Program
{
static void Main(string[] args)
{
String varName = "MyVariable";
int INIT_COUNT = 2;
int MAX_COUNT = 5;
Package pkg = new Package();
Variable var = pkg.Variables.Add(varName, false, "", 0);
Variable var2 = pkg.Variables.Add("Counter", false, "", 0);
ForLoop forLoop = (ForLoop)pkg.Executables.Add("STOCK:ForLoop");
forLoop.InitExpression = "@"+varName+" = "+INIT_COUNT;
forLoop.EvalExpression = "@"+varName+" < "+MAX_COUNT;
forLoop.AssignExpression = "@" + varName + " = @" + varName + " + " + INIT_COUNT;
// Show a different syntax for setting these values.
//forLoop.InitExpression = "@Counter = 1";
//forLoop.AssignExpression = "@Counter = @Counter + 1";
//forLoop.EvalExpression = "@Counter <= 10";
// The ForLoop contains a Properties collection.
// Show how to set some properties using that collection.
forLoop.Properties["Name"].SetValue(forLoop, "ForLoop Container");
forLoop.Properties["Description"].SetValue(forLoop, "ForLoop Container");
// Review the PackagePath of the ForLoop container.
Console.WriteLine("PackagePath: {0}", forLoop.GetPackagePath());
// Because the ForLoop is a container, it can contain tasks
// that run at certain conditions.
TaskHost thLoopMail = (TaskHost)forLoop.Executables.Add("STOCK:SendMailTask");
TaskHost thLoopInsert = (TaskHost)forLoop.Executables.Add("STOCK:BulkInsertTask");
Executables loopExecs = forLoop.Executables;
Console.WriteLine("Number of Executables in ForLoop: {0}", loopExecs.Count);
// Like other containers, precedence constraints can be set on the
// contained tasks.
PrecedenceConstraint pc = forLoop.PrecedenceConstraints.Add((Executable)thLoopMail, thLoopInsert);
PrecedenceConstraints pcs = forLoop.PrecedenceConstraints;
Console.WriteLine("Number of precedence constraints: {0}", pcs.Count);
// Run the package. Because required properties on the tasks are not
// set, current sample code will fail.
DTSExecResult result = pkg.Execute();
}
}
}
Imports System
Imports System.Collections.Generic
Imports System.Text
Imports Microsoft.SqlServer.Dts.Runtime
Imports Microsoft.SqlServer.Dts.Tasks.SendMailTask
Imports Microsoft.SqlServer.Dts.Tasks.BulkInsertTask
Namespace ForLoopAPI
Class Program
'Entry point which delegates to C-style main Private Function
Public Overloads Shared Sub Main()
Main(System.Environment.GetCommandLineArgs())
End Sub
Overloads Shared Sub Main(args() As String)
Dim varName As String = "MyVariable"
Dim INIT_COUNT As Integer = 2
Dim MAX_COUNT As Integer = 5
Dim pkg As New Package()
Dim var As Variable = pkg.Variables.Add(varName, False, "", 0)
Dim var2 As Variable = pkg.Variables.Add("Counter", False, "", 0)
Dim forLoop As ForLoop = CType(pkg.Executables.Add("STOCK:ForLoop"), ForLoop)
forLoop.InitExpression = "@" + varName + " = " + INIT_COUNT
forLoop.EvalExpression = "@" + varName + " < " + MAX_COUNT
forLoop.AssignExpression = "@" + varName + " = @" + varName + " + " + INIT_COUNT
' Show a different syntax for setting these values.
forLoop.InitExpression = "@Counter = 1"
forLoop.AssignExpression = "@Counter = @Counter + 1"
forLoop.EvalExpression = "@Counter <= 10"
' The ForLoop contains a Properties collection.
' Show how to set some properties using that collection.
forLoop.Properties("Name").SetValue(forLoop, "ForLoop Container")
forLoop.Properties("Description").SetValue(forLoop, "ForLoop Container")
' Review the PackagePath of the ForLoop container.
Console.WriteLine("PackagePath: {0}", forLoop.GetPackagePath())
' Because the ForLoop is a container, it can contain tasks
' that run at certain conditions.
Dim thLoopMail As TaskHost = CType(forLoop.Executables.Add("STOCK:SendMailTask"), TaskHost)
Dim thLoopInsert As TaskHost = CType(forLoop.Executables.Add("STOCK:BulkInsertTask"), TaskHost)
Dim loopExecs As Executables = forLoop.Executables
Console.WriteLine("Number of Executables in ForLoop: {0}", loopExecs.Count)
' Like other containers, precedence constraints can be set on the
' contained tasks.
Dim pc As PrecedenceConstraint = forLoop.PrecedenceConstraints.Add(CType(thLoopMail, Executable), thLoopInsert)
Dim pcs As PrecedenceConstraints = forLoop.PrecedenceConstraints
Console.WriteLine("Number of precedence constraints: {0}", pcs.Count)
' Run the package. Because required properties on the tasks are not
' set, current sample code will fail.
Dim result As DTSExecResult = pkg.Execute()
End Sub 'Main
End Class 'Program
End Namespace 'ForLoopAPI
Sample Output:
PackagePath: \Package\{8A18B94E-1176-429E-BB3D-6F3F1E0C9070}
Number of Executables in ForLoop: 2
Number of precedence constraints: 1