Tuples in C#7

Posted: July 29, 2017 in .NET, C#
Tags: , ,

What is a tuple ? -  A tuple is an ordered group of elements.

Tuple has been there as a data type in most of the functional programming languages like Lisp , Haskell since their inception.

For example in Haskell , tuple provides a mechanism to store multiple values together. One key difference with a List is, tuple allows to store multiple values of different data type.

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In C#4.0, Generic Tuple class(es) was introduced, the primary intent was to make it interoperable with languages like Python / F#. This also provided an easy way to return multiple values from a method without defining a separate class or structure.

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The tuple values could be accessed using the Item property of the tuple class as shown below:

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We will tweak the above code as follows:

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We will not be able to modify the element values as these Item properties are read-only making the tuples immutable.

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There are about 8 overloads of Tuple.Create method and 8 Tuple classes allowing us to tuples up to 8 elements.

So far so good , but if I compare the C# snippet with it is Haskell counterpart it looks cumbersome. It looks kludgy , as if some feature has been artificially dumped into the language.

This is further improved in C#7 with elegant syntactic sugar coat and the System.ValueTuple structure doing the work in background.

This feature is now built into the framework (4.7) and if you are using 4.6.2 or earlier,  the package reference to System.ValueTuple needs to be added.

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Like me , if you are using Visual Studio Code you just need to run the command “dotnet add package "System.ValueTuple" from the Terminal, followed by a “dotnet restore”.

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We can now refactor our earlier code using much simpler and more elegant syntax as shown below:

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The tuple values could be accessed similarly using the Item property as shown below:

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We can further improve this by leveraging the new feature of providing tuple element names.

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These element names are used while accessing the values, making the code more readable.

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Unlike Tuple classes , the ValueTuple structure is mutable and it allows us to modify the values.

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The decompiled ( by dotPeek) shows how ValueTuple structure is doing it’s job. The code below looks quite similar to what we did earlier with Tuple class. The named tuple elements are implemented using the attribute System.Runtime.CompilerServices.TupleElementNames. TupleElementNames stores the element names as a string array.

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