Return array of Property from Object Collection

Question

I have a class with this structure:

public class BusinessObject
{
    public int Column1 { get; set; }
    public int Column2 { get; set; }
    public string Column3 { get; set; }
    public int Column4 { get; set; }   
}

and I have a collection of objects of this type call BusinessObjectCollection. If I want an array of values that are distinct for only Column2... what must I do?

What if I dont know the property that I need... so if i have ColumnTitle as a String... and whatever the value of ColumnTitle... I want the distinct values for that property

You mean you want to iterate over the collection (List<BusinessObject> I assume?) and find only those having different Column2 value? — user447356
– user447356, Commented Jul 19, 2011 at 13:01
Yes... I know there is a way to write it using the Distinct function... but I don't know how — Nerd in Training
– Nerd in Training, Commented Jul 19, 2011 at 13:12

Jon Skeet · Accepted Answer · 2011-07-19 13:01:38Z

2

Assuming you want the result to be an IEnumerable<BusinessObject>, so that Column2 is only used for implementing distinctness, there are two options:

Implement IEqualityComparer<BusinessObject> in a way which uses Column2, and pass that into Distinct

Use DistinctBy from MoreLINQ:

var distinct = original.DistinctBy(x => x.Column2);

Obviously the second is simpler, but it does require an extra library (or copying just the code for DistinctBy).

answered Jul 19, 2011 at 13:01

Jon Skeet

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Comments

Marc LaFleur · Accepted Answer · 2011-07-19 13:04:09Z

1

This is the type of stuff that makes me really appreciate LINQ:

int[] distinctColumn2 = (from x in BusinessObjectCollection select x.Column2).Distinct().ToArray();

answered Jul 19, 2011 at 13:04

Marc LaFleur

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2 Comments

Nerd in Training Over a year ago

ok.. this is great! not what if I don't know which Column the user is passing? What if I have e.ItemProperty is being passed (now e.ItemProperty can have either Column1, Column2, Column3 or Column4)?

Nerd in Training Over a year ago

and e.ItemProperty returns a String

Tigran · Accepted Answer · 2011-07-19 13:11:49Z

0

Can use the pure LINQ distinct.

var result = (from bo in lbo select bo.Column2).Distinct();

Where lbo is a collection of BusinessObjects.

Regards.

answered Jul 19, 2011 at 13:11

Tigran

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