using System.Threading.Tasks;

private void PrintMessage() 
{ 
Console.WriteLine("Hello Task library!"); 
}

Task.Factory.StartNew(() => { PrintMessage(); });

Task task = new Task(new Action(PrintMessage));
task.Start();

Task task = new Task(delegate { PrintMessage(); });
task.Start();

Task task = new Task( () => PrintMessage() );
task.Start();

Task task = new Task( () => { PrintMessage(); } );
task.Start();

public async Task DoWork()
{
    await Task.Run(() => PrintMessage());
}

public async Task DoWork()
{
    int res = await Task.FromResult<int>(GetSum(4, 5));   
}
 
private int GetSum(int a, int b)
{
    return a + b;
}