This sample creates a data flow package with an OLEDB Source component feeding into a Lookup Transform. The Lookup transform is set to Full Cache mode, and uses [DimCustomer] as its reference table.

Items of interest:

• CustomerKey and GeographyKey are used as the index (join) columns. This is configured by using the JoinToReferenceColumn property
• The FirstName column is being overwritten by the value retrieved by the lookup transform
• The LastName2 column is being added as a new output column

static void Main(string[] args)
{
    Package package = new Package();

    // Add Data Flow Task
    Executable dataFlowTask = package.Executables.Add("STOCK:PipelineTask");

    // Set the name (otherwise it will be a random GUID value)
    TaskHost taskHost = dataFlowTask as TaskHost;
    taskHost.Name = "Data Flow Task";

    // We need a reference to the InnerObject to add items to the data flow
    MainPipe pipeline = taskHost.InnerObject as MainPipe;

    //
    // Add connection manager
    //

    ConnectionManager connection = package.Connections.Add("OLEDB");
    connection.Name = "localhost";
    connection.ConnectionString = "Data Source=localhost;Initial Catalog=AdventureWorksDW2008;Provider=SQLNCLI10.1;Integrated Security=SSPI;Auto Translate=False;";

    //
    // Add OLEDB Source
    //

    IDTSComponentMetaData100 srcComponent = pipeline.ComponentMetaDataCollection.New();
    srcComponent.ComponentClassID = "DTSAdapter.OleDbSource";
    srcComponent.ValidateExternalMetadata = true;
    IDTSDesigntimeComponent100 srcDesignTimeComponent = srcComponent.Instantiate();
    srcDesignTimeComponent.ProvideComponentProperties();
    srcComponent.Name = "OleDb Source";

    // Configure it to read from the given table
    srcDesignTimeComponent.SetComponentProperty("AccessMode", 0);
    srcDesignTimeComponent.SetComponentProperty("OpenRowset", "[DimCustomer]");

    // Set the connection manager
    srcComponent.RuntimeConnectionCollection[0].ConnectionManager = DtsConvert.GetExtendedInterface(connection);
    srcComponent.RuntimeConnectionCollection[0].ConnectionManagerID = connection.ID;

    // Retrieve the column metadata
    srcDesignTimeComponent.AcquireConnections(null);
    srcDesignTimeComponent.ReinitializeMetaData();
    srcDesignTimeComponent.ReleaseConnections();

    // Add transform
    IDTSComponentMetaData100 lookupComponent = pipeline.ComponentMetaDataCollection.New();
    lookupComponent.ComponentClassID = "DTSTransform.Lookup";
    lookupComponent.Name = "Lookup";

    CManagedComponentWrapper lookupWrapper = lookupComponent.Instantiate();
    lookupWrapper.ProvideComponentProperties();

    // Connect the source and the transform
    IDTSPath100 path = pipeline.PathCollection.New();
    path.AttachPathAndPropagateNotifications(srcComponent.OutputCollection[0], lookupComponent.InputCollection[0]);

    //
    // Configure the transform
    //

    // Set the connection manager
    lookupComponent.RuntimeConnectionCollection[0].ConnectionManager = DtsConvert.GetExtendedInterface(connection);
    lookupComponent.RuntimeConnectionCollection[0].ConnectionManagerID = connection.ID;

    // Cache Type - Full = 0, Partial = 1, None = 2
    lookupWrapper.SetComponentProperty("CacheType", 0);
    lookupWrapper.SetComponentProperty("SqlCommand", "select * from [DimCustomer]");

    // initialize metadata
    lookupWrapper.AcquireConnections(null);
    lookupWrapper.ReinitializeMetaData();
    lookupWrapper.ReleaseConnections();

    // Mark the columns we are joining on
    IDTSInput100 lookupInput = lookupComponent.InputCollection[0];
    IDTSInputColumnCollection100 lookupInputColumns = lookupInput.InputColumnCollection;
    IDTSVirtualInput100 lookupVirtualInput = lookupInput.GetVirtualInput();
    IDTSVirtualInputColumnCollection100 lookupVirtualInputColumns = lookupVirtualInput.VirtualInputColumnCollection;

    // We are joining on CustomerKey and GeographyKey
    // Note: join columns should be marked as READONLY
    var joinColumns = new string[] { "CustomerKey", "GeographyKey" };
    foreach (string columnName in joinColumns)
    {
        IDTSVirtualInputColumn100 virtualColumn = lookupVirtualInputColumns[columnName];
        IDTSInputColumn100 inputColumn = lookupWrapper.SetUsageType(lookupInput.ID, lookupVirtualInput, virtualColumn.LineageID, DTSUsageType.UT_READONLY);
        lookupWrapper.SetInputColumnProperty(lookupInput.ID, inputColumn.ID, "JoinToReferenceColumn", columnName);
    }
    
    // Overwrite the existing FirstName column value with the one returned by the Lookup.
    // To do this, we need to flag the column as READWRITE, and set the CopyFromReferenceColumn property on the input
    var overwriteColumns = new string[] { "FirstName" };
    foreach (string columnName in overwriteColumns)
    {
        IDTSVirtualInputColumn100 virtualColumn = lookupVirtualInputColumns[columnName];
        IDTSInputColumn100 inputColumn = lookupWrapper.SetUsageType(lookupInput.ID, lookupVirtualInput, virtualColumn.LineageID, DTSUsageType.UT_READWRITE);

        lookupWrapper.SetInputColumnProperty(lookupInput.ID, inputColumn.ID, "CopyFromReferenceColumn", columnName);
    }

    // First output is the Match output
    IDTSOutput100 lookupMatchOutput = lookupComponent.OutputCollection[0];

    // Add a new LastName2 column from the "LastName" column returned by the lookup
    var newColumns = new Dictionary<string, string>();
    newColumns.Add("LastName", "LastName2");

    foreach (string sourceColumn in newColumns.Keys)
    {
        string newColumnName = newColumns[sourceColumn];
        string description = string.Format("Copy of {0}", sourceColumn);

        // insert the new column
        IDTSOutputColumn100 outputColumn = lookupWrapper.InsertOutputColumnAt(lookupMatchOutput.ID, 0, newColumnName, description);
        lookupWrapper.SetOutputColumnProperty(lookupMatchOutput.ID, outputColumn.ID, "CopyFromReferenceColumn", sourceColumn);
    }
}