c# Lambda query in list that has a list inside for mapping

Question

Today I'm mapping my objects to DTO like this.

public IEnumerable<ArticleDTO> GetArticlesBasedOnCategorySection(int catSection, int headCategoryID, string customerREFID)
{
    return _articleRepository.GetArticlesByCategory(catSection, headCategoryID, customerREFID).Select(a => Mapper.ToDTO(a)).ToList();
}

But inside the variable I have another list that I want to map in a similar way. Is it possible to write this all in one line like this or do I have to write an foreach loop then map a.List.

Risky Martin · Accepted Answer · 2012-11-28 18:38:31Z

1

How about returning the Article and its items in an anonymous object?

public IEnumerable<ArticleDTO> GetArticlesBasedOnCategorySection(int catSection, int headCategoryID, string customerREFID)
{
    return _articleRepository
        .GetArticlesByCategory(catSection, headCategoryID, customerREFID)
        .Select(a => new 
                     { 
                         Article = Mapper.ToDTO(a),
                         Items = a.Items.Select(b => Mapper.ToDTO(b)).ToList()
                     })
        .ToList();            
}

edited Nov 28, 2012 at 18:38

answered Nov 21, 2012 at 17:06

Risky Martin

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4 Comments

Tan Over a year ago

Sorry but this is not what i´m after. Maybe i have to do a foreach loop after a got the list of article.

Risky Martin Over a year ago

@Tan: What do you want the result to look like? How about you edit the foreach loop version into your question? Then I will be able to help much more easily.

Tan Over a year ago

Your method generated an error so i initated a new List of ArticleDTO and did a foreach loop to fill it out with help of your anonumous list. Thanks!

Risky Martin Over a year ago

@Tan: Good to hear you got it working! However, I'm considering removing this answer because it is incorrect and it still requires you to use a foreach loop. I'll only remove it if it's okay by you, of course.

Risky Martin · Accepted Answer · 2012-11-28 18:41:52Z

One way is to use a lambda that has multiple statements. I'm not sure if this can be considered a one liner, and multi-statement lambdas aren't very LINQ-y.

public IEnumerable<ArticleDTO> GetArticlesBasedOnCategorySection(int catSection, int headCategoryID, string customerREFID)
{
    return _articleRepository
        .GetArticlesByCategory(catSection, headCategoryID, customerREFID)
        .Select(a =>
                {
                    ArticleDTO article = Mapper.ToDTO(a);
                    article.Items = a.Items.Select(b => Mapper.ToDTO(b)).ToList();
                    return article;
                })
        .ToList();
}

If ArticleDTO has a copy constructor you could write it like this:

public IEnumerable<ArticleDTO> GetArticlesBasedOnCategorySection(int catSection, int headCategoryID, string customerREFID)
{
    return _articleRepository
        .GetArticlesByCategory(catSection, headCategoryID, customerREFID)
        .Select(a => new ArticleDTO(Mapper.ToDTO(a))
                     {
                         Items = a.Items.Select(b => Mapper.ToDTO(b)).ToList()
                     })
        .ToList();
}

You could also map the items in a constructor or in Mapper.ToDTO(a).

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