How to flatten object properties using linq

Question

In our localization database we have the following objects:

public class Text
{
  public string Key { get; set; }
  public string LanguageId { get; set; }
  public string Value { get; set; }
}

I need a Linq statment to flatten these records to a structure that has the LanguageIds as a property with the values like:

public class ...
{
  public string Key { get; set; }
  public string En { get; set; }
  public string Ge { get; set; }
  public string Fr { get; set; }
  ...
}

Of course this can be achieved by some elaborate “for each”-ing but there must be a slik Linq statement that does the trick in one go. Any Link Gurus out there?

Do you mean to create a dynamic / ExpandoObject as the output, i.e. your output / projected class will have dynamically created properties? — StuartLC
– StuartLC, Commented Sep 3, 2012 at 8:19
@nonnb: It could be an anonymous object created by the select from the Linq — k.c.
– k.c., Commented Sep 3, 2012 at 8:24
Could you specify more precisely what exact transformation should be done; the input and the output.....It is very difficult to think it over, reading your current question — horgh
– horgh, Commented Sep 3, 2012 at 8:28

Max · Accepted Answer · 2012-11-14 10:52:28Z

I stumbled onto this and just wanted to add my solution to this question. I took the liberty to produce a small runnable example around the expression:

public class LocalizationManager
{
    public IDictionary<string, Localization> LostInTranslation()
    {
        var input = new[]
                        {
                            new Text {Key = "ORDINAL_1", LanguageId = "En", Value = "first"},
                            new Text {Key = "ORDINAL_1", LanguageId = "Fr", Value = "premier"},
                            new Text {Key = "ORDINAL_1", LanguageId = "De", Value = "erste"},
                            new Text {Key = "ORDINAL_2", LanguageId = "En", Value = "second"},
                            new Text {Key = "ORDINAL_2", LanguageId = "Fr", Value = "deuxième"},
                            new Text {Key = "ORDINAL_2", LanguageId = "De", Value = "zweite"},
                            new Text {Key = "ORDINAL_3", LanguageId = "En", Value = "third"},
                            new Text {Key = "ORDINAL_3", LanguageId = "Fr", Value = "troisième"},
                            new Text {Key = "ORDINAL_3", LanguageId = "De", Value = "dritte"},
                        };

        var output =
            input.GroupBy(text => text.Key).Select(
                group =>
                group.Aggregate(new Localization { Key = group.Key },
                                (translation, text) =>
                                    {
                                        translation.GetType().GetProperty(text.LanguageId).SetValue(translation, text.Value, null);
                                        return translation;
                                    }));

        return output.ToDictionary(key => key.Key);
    }
}

public class Text
{
    public string Key { get; set; }
    public string LanguageId { get; set; }
    public string Value { get; set; }
}

public class Localization
{
    public string Key { get; set; }
    public string En { get; set; }
    public string De { get; set; }
    public string Fr { get; set; }
}

Though this appears to be a slight perversion of Aggregate() I think it is true to its spirit. Please note that all languages have to exist as properties on the "Localization" object or you will get a NullReferenceException as GetProperty() returns null.

StuartLC · Accepted Answer · 2013-01-03 05:31:53Z

3

Try the following:

var flattenTexts = texts
    .GroupBy(x => x.Key)
    .Select(x => new { Key = x.Key, 
                       De = x.First(y => y.LanguageId == "De").Value, 
                       En = x.First(y => y.LanguageId == "En").Value 
                     });

You will need to know which languages you have of course...

edited Jan 3, 2013 at 5:31

StuartLC

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answered Sep 3, 2012 at 8:28

Spontifixus

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Comments

akton · Accepted Answer · 2012-09-03 08:21:09Z

0

You can do something like:

typeof(MyClass).GetProperties().AsEnumerable().Select(x => new () {Key = x.Name, En = "English", Ge = "German (shouldn't it be De?)" ... }

answered Sep 3, 2012 at 8:21

akton

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2 Comments

k.c. Over a year ago

Your right about the German Id, but I don't see yet how the Linq is going the produce the result I seek

akton Over a year ago

I misread your question. I thought you wanted to load the values for different languages for different properties on the Text class. The answer @spontifixus is what I'd use.

CloudyMarble · Accepted Answer · 2012-09-03 08:32:57Z

0

If I understood what you mean you can create the second Object out of the 1st one and integrate this in your Linq statement for example:

  var result = TextObjectList.Select(x => new LanguageObject(x))

And in the LanguageObject Constructor set the values up to the LanguageId.

edited Sep 3, 2012 at 8:32

answered Sep 3, 2012 at 8:20

CloudyMarble

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1 Comment

k.c. Over a year ago

I's sure you can combine a result in the select to a new object, the question is how should the Linq be composed before the select: Joins, Unions, etc.

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