Task chaining (wait for the previous task to completed)

var tasks = new List<Task>();

foreach (var guid in guids)
{
    var task = new Task( ...);
    tasks.Add(task);
}

foreach (var task in tasks)
{
    task.Start();
    Task.WaitAll(task);
}

This is run of the UI thread. I need to execute all tasks in tasks variable one after the other. The problem is if I call Task.WaitAll(task), the UI freeze. How can I do the following logic without having the UI freeze?