Coding a Custom Foreach Enumerator
After you have created a class that inherits from the ForEachEnumerator base class, and applied the DtsForEachEnumeratorAttribute attribute to the class, you must override the implementation of the properties and methods of the base class to provide your custom functionality.
For a working sample of a custom enumerator, see ForEachDirectory Sample.
Implementing the Enumerator
Initializing the Enumerator
You can override the InitializeForEachEnumerator method to cache references to the connection managers defined in the package, and to the events interface that you can use to raise errors, warnings, and informational messages.
Validating the Enumerator
The Validate method is overridden to verify that the enumerator is correctly configured. If you return Failure from the method, the enumerator and the package that contains the enumerator will not be executed. The implementation of this method is specific to each enumerator, but if the enumerator relies on Variable or ConnectionManager objects, you should add code to verify that these objects exist in the collections that are provided to the method.
The following code example demonstrates an implementation of Validate that checks for a variable specified in a property of the enumerator.
private string variableNameValue;
public string VariableName
{
get{ return this.variableNameValue; }
set{ this.variableNameValue = value; }
}
public override DTSExecResult Validate(Connections connections, VariableDispenser variableDispenser, IDTSInfoEvents infoEvents, IDTSLogging log)
{
if (!variableDispenser.Contains(this.variableNameValue))
{
infoEvents.FireError(0, "MyEnumerator", "The Variable " + this.variableNameValue + " does not exist in the collection.", "", 0);
return DTSExecResult.Failure;
}
return DTSExecResult.Success;
}
Private variableNameValue As String
Public Property VariableName() As String
Get
Return Me.variableNameValue
End Get
Set (ByVal Value As String)
Me.variableNameValue = value
End Set
End Property
Public Overrides Function Validate(ByVal connections As Connections, ByVal variableDispenser As VariableDispenser, ByVal infoEvents As IDTSInfoEvents, ByVal log As IDTSLogging) As DTSExecResult
If Not variableDispenser.Contains(Me.variableNameValue) Then
infoEvents.FireError(0, "MyEnumerator", "The Variable " + Me.variableNameValue + " does not exist in the collection.", "", 0)
Return DTSExecResult.Failure
End If
Return DTSExecResult.Success
End Function
Returning the Collection
During execution, the ForEachLoop container calls the GetEnumerator method of the custom enumerator. In this method, the enumerator creates and populates its collection of items, and then returns the collection. The ForEachLoop then iterates the items in the collection, and executes its control flow for each item in the collection.
The following example shows an implementation of GetEnumerator that returns an array of random integers.
public override object GetEnumerator()
{
ArrayList numbers = new ArrayList();
Random rand = new Random(DateTime.Now);
for( int x=0; x < 100; x++ )
numbers.Add( rand.Next());
return numbers;
}
Public Overrides Function GetEnumerator() As Object
Dim numbers As ArrayList = New ArrayList()
Dim rand As Random = New Random(DateTime.Now)
Dim x As Integer
For x = 0 To 100- 1 Step x + 1
numbers.Add(rand.Next())
Next
Return numbers
End Function
See Also
Tasks
Creating a Custom Foreach Enumerator
Developing a User Interface for a Custom ForEach Enumerator