Can I cast an action<T> to an action?

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C#

ICommand

Okay, I have to put up my hands and admit I am guilty of copying code (in a hurry) without understanding it.

The code I copied was for an implementation of the System.Windows.Input.ICommand interface. I can't find the source of the code I copied, but reviewing it now, I've decided it looks odd to me.

Here is the code that concerns me.

public class Command : ICommand
{
    public Command( Action<object> execute )
    {
        _execute = execute;
    }

	public Command( Action execute ) : this( (Action<object>)( o => execute() ) )
	{
	}

	private readonly Action<object> _execute = null;
}

It appears to be doing constructor chaining in order to store a parameter of type Action in a variable of type Action<object>. It compiles and the following tests seem to indicate it is working fine:

[TestClass]
public class UTSupportCommand
{
    [TestMethod]
    public void Command_with_Action_parameter_executes()
    {
        Command command = new Command( ActionWithObjectParameter );
        command.Execute( "A" );
        Assert.IsTrue( _t1 == "A" );
    }

    [TestMethod]
    public void Command_with_no_parameter_executes()
    {
        Command command = new Command( ActionWithNoParameter );
        command.Execute( "X" );
        Assert.IsTrue( _t2 == "B" );
    }

    private void ActionWithObjectParameter( object s )
    {
        _t1 = (string)s;
    }

    private void ActionWithNoParameter()
    {
        _t2 = "B";
    }

    private string _t1 = "Z";
    private string _t2 = "Z";
}

What really puzzles me is how I can pass a parameter into the Action that takes no parameter. What happens to it?

I'd appreciate any comments on whether there is anything wrong with this code and what exactly it is doing.

Kind wishes ~ Patrick

What I have tried:

I have tried the tests shown above, which seem to run fine.