CODEWITHSUNDEEP
c#linqlambdatuplesc#-7.3
sɐunıɔןɐqɐp
sɐunıɔןɐqɐp

Reputation: 3512

How to get 'named' tuple components inside Linq queries?

Suppose I have a of tuples, say List<(string, Table)> and I want to iterate over it using a Parallel.ForEach, using the 'named version' of the tuples' components.

The following code does that:

List<(string, Table)> list = new List<(string, Table)>();
Parallel.ForEach(list, tuple => 
{
    (string name, Table table) = tuple;

    // do stuff with components 'name' and 'table' here
});

I want to use name and table, instead of tuple.Item1 and tuple.Item2 respectively, since this makes code more readable. To make that work, I had to declare the tuple components inside the ForEach, if I wanted to use their 'named' versions.


MY QUESTION IS:

Is there a syntax in C# which allows us to get the deconstructed version of the tuple, avoiding that declaration inside the ForEach's body?

And if there is no such syntax, how could we achieve that with extension methods?


I mean, something like this:

List<(string, Table)> list = new List<(string, Table)>();
Parallel.ForEach(list, (string name, Table table) => 
{
    // do stuff with variables 'name' and 'table' here
});

Or maybe this?

List<(string, Table)> list = new List<(string, Table)>();
Parallel.ForEach(list, (name, table) => 
{
    // do stuff with variables 'name' and 'table' here
});


And, if there is a syntax for that, would it also apply to other Linq queries?

E.g.

string[] names = parsed.Select((string name, Table table) => name).ToArray();

Instead of:

string[] names = parsed.Select(t => t.Item1).ToArray();


This would be so nice to have, especially when working with tuples containing several components, e.g. List<(int, string, int, DateTime, ...)>. We would be able to give some context to the tuples' components inside complex Linq queries!

Upvotes: 7

Views: 3559

Answers (4)

Simone
Simone

Reputation: 11797

Not exactly what you want, but this is an alternative to Christoph's answer:

List<(string, Table)> list = new List<(string, Table)>();
Parallel.ForEach(list, ((string name, Table table) t) => 
{
    // do stuff with variables 't.name' and 't.table' here
});

Upvotes: 0

Revious
Revious

Reputation: 8146

You have to use : instead of =

var k = executeResultSet.Select(s => new
{
    IDUser = (int) s["IDUser"],
    SourceCode = s["SourceCode"],
    SourceSystem = s["SourceSystem"]
}).ToList();

var k = executeResultSet.Select(s => 
(
    IDUser: (int) s["IDUser"],
    SourceCode: s["SourceCode"],
    SourceSystem: s["SourceSystem"]
)).ToList();

Upvotes: 2

knagaev
knagaev

Reputation: 2957

It seems to me that you want something like this?

string[] names = parsed.Cast<(string name, Table table)>().Select(p => p.name).ToArray();

Upvotes: 2

Christoph L&#252;tjen
Christoph L&#252;tjen

Reputation: 5804

How to get 'named' tuple components inside Linq queries?

The easiest solution would be to give your items a name, like so

List<(string Name, Table Table)> list = new List<(string, Table)>();
// or simply
var list = new List<(string Name, Table Table)>();

Parallel.ForEach(list, t => 
{
    // do something with t.Name, t.Table
    var name = t.Name;
    var table = t.Table;
});

Is there a syntax in C# which allows us to get the deconstructed version .. inside the ForEach

Afaik no.

Upvotes: 6

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