C#•5mo ago

✅ LINQ, simple query

Is there something I can do to make this query better (faster, more idiomatic, etc)

public record Course(
    string Title,
    string Category,
    int Number,
    DateOnly PublicationDate,
    TimeSpan Duration)
{
    public static readonly Course[] Catalog =
    [
        new Course(
            Title: "Elements of Geometry",
            Category: "MAT", Number: 101, Duration: TimeSpan.FromHours(3),
            PublicationDate: new DateOnly(2009, 5, 20)),
        new Course(
            Title: "Squaring the Circle",
            Category: "MAT", Number: 102, Duration: TimeSpan.FromHours(7),
            PublicationDate: new DateOnly(2009, 4, 1)),
        new Course(
            Title: "Recreational Organ Transplantation",
            Category: "BIO", Number: 305, Duration: TimeSpan.FromHours(4),
            PublicationDate: new DateOnly(2002, 7, 19)),
        new Course(
            Title: "Hyperbolic Geometry",
            Category: "MAT", Number: 207, Duration: TimeSpan.FromHours(5),
            PublicationDate: new DateOnly(2007, 10, 5)),
        new Course(
            Title: "Oversimplified Data Structures for Demos",
            Category: "CSE", Number: 104, Duration: TimeSpan.FromHours(2),
            PublicationDate: new DateOnly(2023, 11, 8)),
        new Course(
            Title: "Introduction to Human Anatomy and Physiology",
            Category: "BIO", Number: 201, Duration: TimeSpan.FromHours(12),
            PublicationDate: new DateOnly(2001, 4, 11)),
    ];
}

class Program
{
    public static void Main()
    {
        
        // all the courses that are 4hrs or longer grouped by their category. What is shown: Title, Course-Number, duration
        var q = Course.Catalog.Where(course => course.Duration.TotalHours >= 4).GroupBy(course => course.Category, course => new { course.Title, course.Number, course.Duration.TotalHours });
        q.Dump();
    }
}

public record Course(
    string Title,
    string Category,
    int Number,
    DateOnly PublicationDate,
    TimeSpan Duration)
{
    public static readonly Course[] Catalog =
    [
        new Course(
            Title: "Elements of Geometry",
            Category: "MAT", Number: 101, Duration: TimeSpan.FromHours(3),
            PublicationDate: new DateOnly(2009, 5, 20)),
        new Course(
            Title: "Squaring the Circle",
            Category: "MAT", Number: 102, Duration: TimeSpan.FromHours(7),
            PublicationDate: new DateOnly(2009, 4, 1)),
        new Course(
            Title: "Recreational Organ Transplantation",
            Category: "BIO", Number: 305, Duration: TimeSpan.FromHours(4),
            PublicationDate: new DateOnly(2002, 7, 19)),
        new Course(
            Title: "Hyperbolic Geometry",
            Category: "MAT", Number: 207, Duration: TimeSpan.FromHours(5),
            PublicationDate: new DateOnly(2007, 10, 5)),
        new Course(
            Title: "Oversimplified Data Structures for Demos",
            Category: "CSE", Number: 104, Duration: TimeSpan.FromHours(2),
            PublicationDate: new DateOnly(2023, 11, 8)),
        new Course(
            Title: "Introduction to Human Anatomy and Physiology",
            Category: "BIO", Number: 201, Duration: TimeSpan.FromHours(12),
            PublicationDate: new DateOnly(2001, 4, 11)),
    ];
}

class Program
{
    public static void Main()
    {
        
        // all the courses that are 4hrs or longer grouped by their category. What is shown: Title, Course-Number, duration
        var q = Course.Catalog.Where(course => course.Duration.TotalHours >= 4).GroupBy(course => course.Category, course => new { course.Title, course.Number, course.Duration.TotalHours });
        q.Dump();
    }
}

12 Replies

reflectronic•5mo ago

for a simple in-memory collection i don't think there is a reason for you to use the element selector you are just taking out a subset of the object, you can just have the groupings contain the objects themselves

Jason_BjornOP•5mo ago

you mean the new {} part?

reflectronic•5mo ago

var q = Course.Catalog.Where(course => course.Duration.TotalHours >= 4).GroupBy(course => course.Category);

var q = Course.Catalog.Where(course => course.Duration.TotalHours >= 4).GroupBy(course => course.Category);

Jason_BjornOP•5mo ago

Well, let's say I want that information I could use a tuple instead That way I have a value tuple/struct instead of a class

reflectronic•5mo ago

you can get that information by looking at the Course objects instead they have the information right there

Jason_BjornOP•5mo ago

Look at them after the query?

reflectronic•5mo ago

then you don't have to make anything if q is an IGrouping<string, Course>, then you have all the Course objects from which you can get Title, Number, and TotalHours you can do IGrouping<string, (string Title, int Number, double TotalHours)> but those values are trivial to get from the Course object, selecting them out does not really improve the code

Jason_BjornOP•5mo ago

@reflectronic like this

var q = Course.Catalog.Where(course => course.Duration.TotalHours >= 4).GroupBy(course => course.Category);
        foreach (var categoryGroup in q)
        {
            foreach (var course in categoryGroup)
            {
                Console.WriteLine($"{course.Title}, {course.Number}, {course.Duration.TotalHours}");
            }
        }

var q = Course.Catalog.Where(course => course.Duration.TotalHours >= 4).GroupBy(course => course.Category);
        foreach (var categoryGroup in q)
        {
            foreach (var course in categoryGroup)
            {
                Console.WriteLine($"{course.Title}, {course.Number}, {course.Duration.TotalHours}");
            }
        }

reflectronic•5mo ago

right

Jason_BjornOP•5mo ago

so this is better than `new {} because it doesn't create any new data structures, it just links to existing ones or what?

Salman•5mo ago

right, you don't really need to create a new object for each record apparently

Jason_BjornOP•5mo ago

thanks

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✅ LINQ, simple query