Gathering a List for the ForEach Loop with the Script Task

更新日期： 2006 年 4 月 14 日

The Foreach from Variable Enumerator enumerates over the items in a list that is passed to it in a variable and performs the same tasks on each item. You can use custom code in a Script task to populate a list for this purpose. For more information about the enumerator, see Foreach 循环容器.

注意：
If you want to create a task that you can more easily reuse across multiple packages, consider using the code in this Script task sample as the starting point for a custom task. For more information, see Developing a Custom Task.

Description

The following example uses methods from the System.IO namespace to gather a list of Excel workbooks on the computer that are either newer or older than a number of days specified by the user in a variable. It searches directories on Drive C recursively for files that have the .xls extension and examines the date on which each file was last modified to determine whether the file belongs in the list. It adds qualifying files to an ArrayList and saves the ArrayList to a variable for later use in a Foreach Loop container. The Foreach Loop container is configured to use the Foreach from Variable enumerator.

注意：

The variable that you use with the Foreach from Variable Enumerator must be of type Object. The object that you place in the variable must implement one of the following interfaces: System.Collections.IEnumerable, System.Runtime.InteropServices.ComTypes.IEnumVARIANT, System.ComponentModel IListSource, or Microsoft.SqlServer.Dts.Runtime.Wrapper.ForEachEnumeratorHost. An Array or ArrayList is commonly used. The ArrayList requires a reference and an Imports statement for the System.Collections namespace.

You can experiment with this task by using different positive and negative values for the FileAge package variable. For example, you can enter 5 to search for files created in the last five days, or enter -3 to search for files that were created more than three days ago. This task may take a minute or two on a drive with many folders to search.

To configure this Script Task example

1. Create a package variable named FileAge of type integer and enter a positive or negative integer value. When the value is positive, the code searches for files newer than the specified number of days; when negative, for files older than the specified number of days.

2. Create a package variable named FileList of type Object to receive the list of files gathered by the Script task for later use by the Foreach from Variable Enumerator.

3. Add the FileAge variable to the Script task's ReadOnlyVariables property, and add the FileList variable to the ReadWriteVariables property.

4. In your code, import the System.Collections and the System.IO namespaces.

Code

Imports System
Imports System.Data
Imports System.Math
Imports Microsoft.SqlServer.Dts.Runtime
Imports System.Collections
Imports System.IO

Public Class ScriptMain

  Private Const FILE_AGE As Integer = -50

  Private Const FILE_ROOT As String = "C:\"
  Private Const FILE_FILTER As String = "*.xls"

  Private isCheckForNewer As Boolean = True
  Dim fileAgeLimit As Integer
  Private listForEnumerator As ArrayList

  Public Sub Main()

    fileAgeLimit = DirectCast(Dts.Variables("FileAge").Value, Integer)

    ' If value provided is positive, we want files NEWER THAN n days.
    '  If negative, we want files OLDER THAN n days.
    If fileAgeLimit < 0 Then
      isCheckForNewer = False
    End If
    ' Extract number of days as positive integer.
    fileAgeLimit = Math.Abs(fileAgeLimit)

    listForEnumerator = New ArrayList

    GetFilesInFolder(FILE_ROOT)

    ' Return the list of files to the variable
    '  for later use by the Foreach from Variable enumerator.
    System.Windows.Forms.MessageBox.Show("Matching files: " & listForEnumerator.Count.ToString, "Results", Windows.Forms.MessageBoxButtons.OK, Windows.Forms.MessageBoxIcon.Information)
    Dts.Variables("FileList").Value = listForEnumerator

    Dts.TaskResult = Dts.Results.Success

  End Sub

  Private Sub GetFilesInFolder(ByVal folderPath As String)

    Dim localFiles() As String
    Dim localFile As String
    Dim fileChangeDate As Date
    Dim fileAge As TimeSpan
    Dim fileAgeInDays As Integer
    Dim childFolder As String

    Try
      localFiles = Directory.GetFiles(folderPath, FILE_FILTER)
      For Each localFile In localFiles
        fileChangeDate = File.GetLastWriteTime(localFile)
        fileAge = DateTime.Now.Subtract(fileChangeDate)
        fileAgeInDays = fileAge.Days
        CheckAgeOfFile(localFile, fileAgeInDays)
      Next

      If Directory.GetDirectories(folderPath).Length > 0 Then
        For Each childFolder In Directory.GetDirectories(folderPath)
          GetFilesInFolder(childFolder)
        Next
      End If

    Catch
      ' Ignore exceptions on special folders such as System Volume Information.
    End Try

  End Sub

  Private Sub CheckAgeOfFile(ByVal localFile As String, ByVal fileAgeInDays As Integer)

    If isCheckForNewer Then
      If fileAgeInDays <= fileAgeLimit Then
        listForEnumerator.Add(localFile)
      End If
    Else
      If fileAgeInDays > fileAgeLimit Then
        listForEnumerator.Add(localFile)
      End If
    End If

  End Sub

End Class

Change History

Release	History
2006 年 4 月 14 日	New content: Explained requirements for the variable used with the Foreach from Variable Enumerator.

请参阅

其他资源

Foreach 循环容器
如何配置 Foreach 循环容器
添加和配置 Foreach 循环容器

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