Void Destination

The Void destination can be used to discard records

Void Destination#

The VoidDestination<T> is a special destination that discards incoming records. It is useful when you need to filter out data in a flow while ensuring that all records are processed correctly. Since every record in a dataflow must reach a destination for execution to complete, the VoidDestination helps handle unwanted records without blocking the pipeline.

This component is part of the ETLBox core package and does not require additional dependencies.

Usage#

A common use case for VoidDestination is filtering records in a dataflow. Any records that do not match a condition can be sent to the VoidDestination instead of being stored.

public class MyRow
{
    public int Value { get; set; }
}

var source = new CsvSource<MyRow>("test.txt");
var destKeep = new MemoryDestination<MyRow>();
var destVoid = new VoidDestination<MyRow>();

source.LinkTo(destKeep, row => row.Value > 10);
source.LinkTo(destVoid, row => row.Value <= 10);

Network.Execute(source);

Implicit Use#

Instead of explicitly defining a VoidDestination, you can use the third parameter of LinkTo() to automatically discard records that do not match a condition.

public class MyRow
{
    public int Value { get; set; }
}

var source = new CsvSource<MyRow>("test.txt");
var destKeep = new MemoryDestination<MyRow>();

source.LinkTo(destKeep, row => row.Value > 10, row => row.Value <= 10);

Network.Execute(source);

Automatic Complement Void Links#

If a network contains predicate-based links or void predicate links, some data might not be sent to any component. Since ETLBox waits for all records to be processed, an incomplete network can cause execution to hang indefinitely.

To prevent this, setting TryAddComplementVoidLinks = true on the network ensures that a complementary void link is automatically added for each predicate link, ensuring that all data flows to a component.

Example#

var source = new MemorySource<MyRow>();
source.DataAsList = new List<MyRow> {
    new MyRow { Value = 5 },
    new MyRow { Value = 15 },
    new MyRow { Value = 25 }
};

var destLow = new MemoryDestination<MyRow>();
var destHigh = new MemoryDestination<MyRow>();

source.LinkTo(destLow, row => row.Value < 10);
source.LinkTo(destHigh, row => row.Value > 20);

var network = Network.Init(source);
network.TryAddComplementVoidLinks = true;
await network.ExecuteAsync();

• The first link sends rows with Value < 10 to destLow.
• The second link sends rows with Value > 20 to destHigh.
• The row with Value = 15 is not covered by any predicate, which would normally cause the network to hang.
• Setting TryAddComplementVoidLinks = true automatically adds a void link for uncovered records, ensuring the execution completes successfully.