[C# tips] #1 Operate arrays like SQL

C# is not useful than Java. Why don’t we use Java, which runs on 3 billion devices!

Well… C#? Is it used to call Win API…?

These are what I have really been told about C#.
When I listened them, I realized that many people haven’t ever touched C# yet. Indeed, there are situations where you should not use C#. I think, however, there should be much more people who use C# even considering it.
I have thought deeply and dicided: “I’m going to show C# tips everyday on my blog!”

That’s why I started “Today’s C# tips”. This is the first article.
(After a munite, I noticed it is hard to write everyday. I changed it every three days…)

Main story Link to heading

Today’s main dish is the C# syntax which looks like SQL.
(If you know that, ~~you should close this page and save your time~~.)

Working with SQL Link to heading

What do you associate SQL with?
It may be:

A kind of the tool for operating databases
an initialism of Structured Query Language
My SQL, Azure, Postgres, Oracle…

SQL is a language which specialize to manipulate databases. (And also I haven’t heard somebody makes a game using it!) We will see the situation which SQL play an active part.

Table name : TestResults

math	physics	name
50	100	A
60	70	B
80	80	C
40	90	D

We have a table and want to extract those whose math is 50 or more and sort them in descending order of the value of physics. On this time, the following one is a SQL code which works as expected.

SELECT math, physics
FROM TestResults
WHERE math >= 50
ORDER BY physics DESC;

I don’t describe more about SQL so if you want to know more, you should google.

Can it be done by C#? Link to heading

Yes! Use System.Linq to do that.

I used List<> and Tuple to express data. Sorry for the people who loves anonymous types.

// using System;
// using System.Collections.Generic;

var testResults = new List<(int math, int physics, string name)>() {
    (50, 100, "A"),
    (60, 70, "B"),
    (80, 80, "C"),
    (40, 90, "D")
};

And here is the code which is equivalent to the previous SQL code.

// using System.Linq;

var selected = from result in testResults
    where result.math >= 50
    orderby result.physics descending
    select result;

SELECT math, physics
FROM TestResults
WHERE math >= 50
ORDER BY physics DESC;

Compare them. Of course, there are small differences such as the usage of Select or in. However, They look alike each other, aren’t they?

It is certain that you can write C# code like SQL.

But many people use… Link to heading

I told you about a SQL-like syntax for long time, but it’s not a popular way to do so. Many people use some functions instead of it:

var selected = testResults
    .Where(result => result >= 50)
    .OrderByDescending(result => result.physics);

~~I often use this and recommend this.~~ There are nothing which cannot do but with SQL-like syntax.

That’s it.
Have a nice C# day!