Does linking keep the linked block alive?

Question

When using System.Threading.Tasks.Dataflow, if I link block a to block b, will the link keep b alive? Or do I need to keep a reference to b around to prevent it from being collected?

internal class SomeDataflowUser
{
    public SomeDataflowUser()
    { 
        _a = new SomeBlock();
        var b = new SomeOtherBlock();
        _a.LinkTo(b);
    }

    public void ReactToIncomingMessage( Something data )
    {    
        // might b be collected here?
        _a.Post( data );
    }

    private ISourceBlock<Something> _a;
}

Answer 1

In addition to @Eric great explanation of GC behavior I want to address the special case related to TPL-Dataflow. You can easily see the behavior that LinkTo yields from a simple test. Notice that nothing, to my knowledge, is holding on to b except for its link to a.

[TestFixture]
public class BlockTester
{

    private int count;

    [Test]
    public async Task Test()
    {
        var inputBlock = BuildPipeline();
        var max = 1000;
        foreach (var input in Enumerable.Range(1, max))
        {
            inputBlock.Post(input);
        }
        inputBlock.Complete();

        //No reference to block b
        //so we can't await b completion
        //instead we'll just wait a second since
        //the block should finish nearly immediately
        await Task.Delay(TimeSpan.FromSeconds(1));
        Assert.AreEqual(max, count);
    }

    public ITargetBlock<int> BuildPipeline()
    {
        var a = new TransformBlock<int, int>(x => x);
        var b = new ActionBlock<int>(x => count = x);
        a.LinkTo(b, new DataflowLinkOptions() {PropagateCompletion = true});
        return a;
    }
}