How to get first 5 questions of list?

Question

I'm trying to create a quiz program but at the moment I have a list for each category. I would like to use the same list and just call the categories I want in each quiz.

private void LoadQuestions()
        {
            Question q1 = new Question
            {
                NameOfQuestion = "Vem är världens bästa golfspelare?",
                Options = new List<string>() { "Tiger Woods", "Matt Kuchar", "S.H. Kim", "Adam Scott" },
                Answer = "Tiger Woods",
                Category = "Golf"
            };

            Question q2 = new Question
            {
                NameOfQuestion = "Vad heter Rory i efternamn?",
                Options = new List<string>() { "Svensson", "Mcilroy", "Eriksson", "Smith" },
                Answer = "Mcilroy",
                Category = "Golf"
            };

            Question q3 = new Question
            {
                NameOfQuestion = "Hur många golfhål spelar man under en tävling?",
                Options = new List<string>() { "18", "26", "72", "180" },
                Answer = "72",
                Category = "Golf"
            };

            Question q4 = new Question
            {
                NameOfQuestion = "Vilken bana spelas Masters på?",
                Options = new List<string>() { "TPC Sawgrass", "Agusta", "Halmstad GK", "The Country Club" },
                Answer = "Agusta",
                Category = "Golf"
            };

            Question q5 = new Question
            {
                NameOfQuestion = "Vad har Gustav i HCP?",
                Options = new List<string>() { "Alldeles för högt", "Alldeles för lågt", "Han är bäst", "Han är sämst" },
                Answer = "Han är sämst",
                Category = "Golf"
            };

            Question q6 = new Question
            {
                NameOfQuestion = "Hur många spelare är på isen samtidigt?",
                Options = new List<string>() { "8", "10", "6", "12" },
                Answer = "12",
                Category = "Hockey"
            };

            Question q7 = new Question
            {
                NameOfQuestion = "Hur lång är en hockeymatch?",
                Options = new List<string>() { "40 minuter", "60 minuter", "90 minuter", "45 minuter" },
                Answer = "60 minuter",
                Category = "Hockey"
            };

            Question q8 = new Question
            {
                NameOfQuestion = "Hur många poäng får ett lag om de vinner i övertid?",
                Options = new List<string>() { "3", "4", "2", "1" },
                Answer = "2",
                Category = "Hockey"
            };

            Question q9 = new Question
            {
                NameOfQuestion = "Vilken färg har en hockeypuck?",
                Options = new List<string>() { "Mörkblå", "Svart", "Grå", "Svart & vit" },
                Answer = "Svart",
                Category = "Hockey"
            };

            Question q10 = new Question
            {
                NameOfQuestion = "Vad kallas det när det står 40-40 i tennis?",
                Options = new List<string>() { "Even", "All square", "Deuce", "Even Steven" },
                Answer = "Deuce",
                Category = "Tennis"
            };

            Question q11 = new Question
            {
                NameOfQuestion = "Vad heter den kända svensken som tog 11 grand slam-segrar?",
                Options = new List<string>() { "Björn Borg", "Stefan Edberg", "Gustav Eriksson", "Mats Wilander" },
                Answer = "Björn Borg",
                Category = "Tennis"
            };

            Question q12 = new Question
            {
                NameOfQuestion = "Vart föddes den kända tennisspelaren Andy Murray?",
                Options = new List<string>() { "Wales", "England", "Scotland", "Ireland" },
                Answer = "Scotland",
                Category = "Tennis"
            };

            Question q13 = new Question
            {
                NameOfQuestion = "Vad kallas det kända mästerskap som spelas i England varje år?",
                Options = new List<string>() { "Wimbledon", "Offerthon", "English Tennis Cup", "London Tennis Championship" },
                Answer = "Wimbledon",
                Category = "Tennis"
            };

            Question q14 = new Question
            {
                NameOfQuestion = "Avsluta meningen: Game, Set &    ",
                Options = new List<string>() { "Victory", "Relax", "Time to make your bet", "Match" },
                Answer = "Match",
                Category = "Tennis"
            };

            Question q15 = new Question
            {
                NameOfQuestion = "Vilken låt är den mest strömmade på spotify?",
                Options = new List<string>() { "The Weeknd - Blinding Lights", "Ed Sheeran - Shape Of You", "Tones And I - Dance Monkey", "Post Malone - Rockstar" },
                Answer = "The Weeknd - Blinding Lights",
                Category = "Music"
            };

            Question q16 = new Question
            {
                NameOfQuestion = "Vilket band har gjort låten: Smoke on the water?",
                Options = new List<string>() { "Europe", "Iron Maiden", "Rolling Stones", "Deep Purple" },
                Answer = "Deep Purple",
                Category = "Music"
            };

            Question q17 = new Question
            {
                NameOfQuestion = "Vilken är Avicii's mest streamade låt på spotify?",
                Options = new List<string>() { "The Nights", "The Days", "Wake Me Up", "Without you" },
                Answer = "Wake Me Up",
                Category = "Music"
            };

            Question q18 = new Question
            {
                NameOfQuestion = "The Beatles är otroligt känt band med bandmedlemmar som John Lennon, Ringo Starr och Paul McCartney. Vad heter den fjärde medlemmen?",
                Options = new List<string>() { "George Harisson", "Dean Smith", "George Davidson", "Terry McDavid" },
                Answer = "George Harisson",
                Category = "Music"
            };

            Question q19 = new Question
            {
                NameOfQuestion = "Elvis Presley performed the song Hound dog. Please continue the lyrics to the song: You ain't nothing but a hound dog:",
                Options = new List<string>() { "Party'n all the time", "Lying all the time", "Crying all the time", "Smiling everytime" },
                Answer = "Crying all the time",
                Category = "Music"
            };

            Question q20 = new Question
            {
                NameOfQuestion = "Who performed the song: Like a virgin?",
                Options = new List<string>() { "Madonna", "Rihanna", "Britney Spears", "Cher" },
                Answer = "Madonna",
                Category = "Music"
            };

            Question q21 = new Question
            {
                NameOfQuestion = "Walter White är en högskolelärare som börjar att tillverka droger. Vad heter denna serie?",
                Options = new List<string>() { "Game Of Thrones", "Drugs & Teach", "Breaking Bad", "Cocaine & Clementine" },
                Answer = "Breaking Bad",
                Category = "Film & TV-Serie"
            };

            Question q22 = new Question
            {
                NameOfQuestion = "I sagan om ringen finns det en liten hobbit som blivit förvriden av mörkret. Han mumlar ofta: my precious... Vad heter denna karaktär?",
                Options = new List<string>() { "Smeagol", "Reagol", "Chero", "Mearo" },
                Answer = "Smeagol",
                Category = "Film & TV-Serie"
            };

            Question q23 = new Question
            {
                NameOfQuestion = "Vilken film har högst betyg på rating-sidan IMDB?",
                Options = new List<string>() { "Gudfadern", "The Dark Knight", "Nyckeln till frihet", "Schindler's List" },
                Answer = "Nyckeln till frihet",
                Category = "Film & TV-Serie"
            };

            Question q24 = new Question
            {
                NameOfQuestion = "Vilken TV-serie har högst betyg på rating-sidan IMDB?",
                Options = new List<string>() { "Planet Earth", "Planet Earth II", "Breaking Bad", "Band of Brothers" },
                Answer = "Planet Earth II",
                Category = "Film & TV-Serie"
            };

            Question q25 = new Question
            {
                NameOfQuestion = "Vad heter det svenska företaget som fram till 2012 tillverkade bilar? De kanske är mest kända för sina flygplan.",
                Options = new List<string>() { "Volvo", "Audi", "Saab", "Gripen" },
                Answer = "Saab",
                Category = "Bilar"
            };

            Question q26 = new Question
            {
                NameOfQuestion = "Vad heter företaget från Ängelholm som tillverkar världens snabbaste bilar?",
                Options = new List<string>() { "Hyundai", "Roendi", "Polestar", "Koenigsegg" },
                Answer = "Koenigsegg",
                Category = "Bilar"
            };

            Question q27 = new Question
            {
                NameOfQuestion = "Volvo är ett stort bilföretag som är baserat i Göteborg, Sverige. Men vad betyder volvo på latin?",
                Options = new List<string>() { "Säkerhet", "Jag rullar", "Snabb och kompakt", "Säkert rullande" },
                Answer = "Jag rullar",
                Category = "Bilar"
            };

            Question q28 = new Question
            {
                NameOfQuestion = "Vad heter det kända Italienska bilmärket som är kända för sin röda färg?",
                Options = new List<string>() { "Lamborghini", "Rolls Royce", "Audi", "Ferrari" },
                Answer = "Ferrari",
                Category = "Bilar"
            };

            Question q29 = new Question
            {
                NameOfQuestion = "Vilket är världens mest sålda TV-spel?",
                Options = new List<string>() { "Counter Strike: Global Offensive", "Minecraft", "World Of Warcraft", "Grand Theft Auto V" },
                Answer = "Minecraft",
                Category = "TV-Spel"
            };

            Question q30 = new Question
            {
                NameOfQuestion = "Vad heter Mario's bror?",
                Options = new List<string>() { "Bowser", "Toad", "Luigi", "Yoshi" },
                Answer = "Luigi",
                Category = "TV-Spel"
            };

            Question q31 = new Question
            {
                NameOfQuestion = "Vilken svensk skapade Minecraft?",
                Options = new List<string>() { "Markus Persson", "Daniel Ek", "Joakim Larsson", "Max Pettersson" },
                Answer = "Markus Persson",
                Category = "TV-Spel"
            };

            Question q32 = new Question
            {
                NameOfQuestion = "Battle Royale är ett populärt läge. Det innebär att man möter andra lag och laget som är kvar sist vinner. Vilket är det populäraste Battle Royale Spelet?",
                Options = new List<string>() { "Fortnite", "Apex Legends", "PUBG: Battlegrounds", "Call Of Duty: Warzone" },
                Answer = "PUBG: Battlegrounds",
                Category = "TV-Spel"
            };

            Questions.AddRange(new List<Question> { q1, q2, q3, q4, q5, q6, q7, q8, q9, q10, q11, q12, q13, q14, q15, q16, q17, q18, q19, q20, q21, q22, q23, q24, q25, q26, q27, q28, q29, q30, q31, q32 });
        }

This is the list I would like to use, but I'm not sure how to only call the golf questions or how to only call the movies questions etc.

Right now I have a list for each category, so I'm calling the lists in blazor like this:

        @if (questionIndex5 < QuestionsGolf.Count)
        {
                <div class="app-title">
                    @QuestionsGolf[questionIndex5].Category
                </div>
                <div class="quiz-header">
                    @QuestionsGolf[questionIndex5].NameOfQuestion
                </div>
                <div class="quiz-body">
                    @foreach (var option2 in QuestionsGolf[questionIndex5].Options)
                    {
                        <OptionCard Option="@option2" OnOptionSelected="OptionSelectedSolo"></OptionCard>   
                    }
                </div>
        }

questionIndex5 is just declared as 0 and it ++'s when selecting an option in OnOptionSelected.

Anyone got any tips for me how too proceed? :)

Answer 1

The other answers already tell you how to filter by category:

IEnumerable<Question> golfQuestions = Questions
    .Where(question => question.Category.Equals("Golf"));

// or
List<Question> golfQuestionList = Questions
    .Where(question => question.Category.Equals("Golf"))
    .ToList();

You seem to be confused how to display this. Often, when working with Lists / IEnumerables we want to display all of them. This could look something like this:

@foreach (Question question in golfQuestions)
{
    <div class="app-title">
        @question.Category
    </div>
    <div class="quiz-header">
        @question.NameOfQuestion
    </div>
    <div class="quiz-body">
        @foreach (var option2 in question.Options)
        {
            <OptionCard Option="@option2" OnOptionSelected="OptionSelectedSolo">
            </OptionCard>   
        }
    </div>
}

If you only want to display a single question, converting to an IEnumerable makes little sense. I would suggest adding .ToArray(), but .ToList() works as well. Here is an example of displaying the third golf question:

Question[] golfQuestions = Questions
    .Where(question => question.Category.Equals("Golf"))
    .ToArray();

Question myQuestion = gofQuestions[2];


<div class="app-title">
    @myQuestion.Category
</div>
...

Answer 2

You can create a method using the LINQ method Where to achieve this:

private IEnumerable<Question> GetQuestionsForCategory(string category)
{
    return Questions.Where(x => x.Category == category)
}

Answer 3

You can use where Questions.Where(x => x.Category == "Golf") Or if you need to group questions by category then - Questions.GroupBy(x => x.Category) -- with this solution you will get all questions grouped into lists by their category

Answer 4

Anyone got any tips for me how too proceed? :)

Here's a slightly different implementation of your code that demonstrates some of the principles and patterns you can apply to help structure what your trying to do.

First a service for your data. You need to separate out the actual data pipeline from you UI. I use records to make the data in the data pipeline immutable (Read Only).

Your data object:

public record Question
{
    public string NameOfQuestion { get; init; } = string.Empty;
    public IEnumerable<string> Options { get; init; } = Enumerable.Empty<string>();
    public string Answer { get; init; } = string.Empty;
    public string Category { get; init; } = string.Empty;
}

Here's a demo QuestionProvider. Normally this will interface with a database or API so I've made it async.

public class QuestionProvider
{
    private List<Question> _questions = new();

    public Task Loading = Task.CompletedTask;

    public QuestionProvider()
        => this.Loading = this.LoadQuestions();

    public async ValueTask<IEnumerable<Question>> GetQuestions(QuestionQueryRequest request)
    {
        // Pretend I'm an async database or an API call
        await Task.Delay(100);
        var query = _questions.AsEnumerable();
        if (request.Category is not null)
            query = query.Where(item => item.Category.Equals(request.Category, StringComparison.CurrentCultureIgnoreCase));
        
        return query;
    }

    public async ValueTask<IEnumerable<string>> GetCategories()
    {
        await Task.Delay(100);
        return _questions.DistinctBy(item => item.Category).Select(item => item.Category);
    }
    private async Task LoadQuestions()
    {
        Question q1 = new Question
        {
            NameOfQuestion = "Vem är världens bästa golfspelare?",
            Options = new List<string>() { "Tiger Woods", "Matt Kuchar", "S.H. Kim", "Adam Scott" },
            Answer = "Tiger Woods",
            Category = "Golf"
        };
        // your existing code

        // pretend I'm a async task
        await Task.Delay(100);
    }
}

And then the View to manage the data for the UI page/component:

public class QuestionPresenter
{
    private readonly QuestionProvider _questionProvider;
    private bool _hasLoaded;
    public IEnumerable<string> Categories = Enumerable.Empty<string>();

    public string? Category { get; set; }

    public IEnumerable<Question> Questions { get; private set; } = Enumerable.Empty<Question>();

    public QuestionPresenter(QuestionProvider questionProvider)
        => _questionProvider = questionProvider;

    public async ValueTask GetQuestions()
    {
        // ensure the provider has loaded completely
        if (!_hasLoaded)
            await _questionProvider.Loading;

        this.Questions = await _questionProvider.GetQuestions(new(this.Category));
    }

    public async ValueTask Load()
    {
        // ensure the provider has loaded completely
        await _questionProvider.Loading;
        _hasLoaded= true;
        this.Categories = await _questionProvider.GetCategories();
    }
}

Service registration:

builder.Services.AddScoped<QuestionProvider>();
builder.Services.AddTransient<QuestionPresenter>();

And finally a page to get and display the data:

@page "/"
@inject QuestionPresenter Presenter
<PageTitle>Index</PageTitle>

<select class="form-select" value="@this.Presenter.Category" @onchange=SetCategory>
    @if (this.Presenter.Category is null)
    {
        <option selected disabled value="">-- Select a Category --</option>
    }
    @foreach (var category in Presenter.Categories)
    {
        <option value="@category">@category</option>
    }

</select>

@foreach (var question in this.Presenter.Questions)
{
    <div class="bg-light p-2 m-2">
        <div>
            Question: @question.NameOfQuestion
        </div>
        <div>
            Options: @OptionsList(question.Options)
        </div>
        <div>
            Answer: @question.Answer
        </div>
    </div>

}

@code {
    protected async override Task OnInitializedAsync()
        => await this.Presenter.Load();

    private async Task SetCategory(ChangeEventArgs e)
    {
        this.Presenter.Category = e.Value?.ToString() ?? null;
        if (this.Presenter.Category is not null)
            await Presenter.GetQuestions();
    }

    private RenderFragment<IEnumerable<string>> OptionsList => list => __builder =>
    {
        foreach(var item in list)
        {
            <span>&nbsp; @item;</span>
        }
    };
}