Task.Unwrap() - A useful proxy to avoid inner Task inside a Task

In this post we will talk about Task and what we should do when we end up with 'Task<Task<Foo>>".

Let's start with a simple example. Let's asume that we have an async method.

public async Task<int> DoSomethingAsync()
{
    return await GetNumberAsync();
}

We have the 'DoSomethingAsync' method that we need to call inside another task. If we call this method directly we will end up with Task<int>, but if we call this method in another Task than we will end up with...

Task<int> simpleCall = DoSomethingAsync();

Task<Task<int>> complexCall = new Task<Task<int>>(
    async () =>
    {
        return await DoSomethingAsync();
    });

As we can see, to be able to call a async a method in a task we will need to add the 'async' attribute to the lambda expression (function). Because of this we will get a Task of Task (Task<Task<..>) and not a simple Task<...>.

You could say that this is fine, it is not complicated to get the result of the inner task and so on. Yes, this is true, but in the same time we need to be able to handle error from both tasks and cancelation tokens.
For this cases it is recommended to use "Task.Unwrap" method, that allow us to work directly with Task<...>.

Task<int> simpleCall = DoSomethingAsync();

Task<Task<int>> complexCall = new Task<Task<int>>(
    async () =>
    {
        return await DoSomethingAsync();
    });
complexCall.Start();
Task<int> complexCallUnwrap = complexCall.Unwrap();

There is no magic behind 'Unwrap' method. You can use with success in cases when you have Task<Task<Task<...>,  also.
Behind the scene, 'Unwrap' method creates a proxy that will handle all complex cases for us. We don't need to forward the cancelation token, to check errors at different level. We can work as we would have a simple task, not a task inside another tasks.
The Task that is returned by 'Unwrap' includes all the cancelation token request and exception handling (the proxy is doing the job of connecting the task with inner task).

Another use case when 'Unwrap' is useful is in the moment when we want to create a continue action using 'ContinueWith' method. Without 'Unwrap' method we can end up easily in cases where we have inner Task inside a task. This can be avoided using 'Unwrap'.

Task<Task<int>> taskInTask = DoSomethingAsync()
                                .ContinueWith((value) => DoSomethingAsync());
Task<int> taskInTaskWithUnwrap = DoSomethingAsync()
                                            .ContinueWith((value) => DoSomethingAsync())
                                            .Unwrap();

Using 'Unwrap' method we can work directly with a proxy, that represents the entire Task<Task>, like a simple Task.