# Chainable operations in a Continuation flow

The use of chained operations in C# is nothing new, we uses this feature in several different libraries.

Any method that returns an instance of itself is a fluent method, then, is capable of creates continuous process. Once again we can see this type of implementation in the [`System.Linq`](https://msdn.microsoft.com/pt-br/library/system.linq\(v=vs.100\).aspx) namespace. With this namespace you can perform a filtering and a transformation through the methods `Where` and `Select` in a chainable operation, see an example:

```csharp
IEnumerable<int> values = Enumerable.Range(0,10)
values.Where(value => value % 2 == 0)
      .Select(value => value * value);
```

As the previous example shows, it is possible to make several consecutive calls on a single command line. This is what we call a continuous or fluent process.

The **Tango** implements this feature in several types and modules, like `Option`, `Either` and even `IEnumerable`.

In addition, there's a special object called `Continuation`. This object is used mainly to this type of fluent process, but dealing with a success and a fail outputs.
