Codepolice.net » LINQ

IN queries with LINQ to SQL

Ola — Tue, 01 Jun 2010 13:33:12 +0000

This is another awesome feature in LINQ to SQL that i always forget about. Sometimes you have an array of strings or any other type and want to query the database for all values that have one of the values in the array.

string platform = "windows|linux";
string[] platformList = platform.Split('|');
itemQuery = from m in itemQuery
from p in m.PlattformItemRelations
where platformList.Contains(p.Plattform.Text.ToLower())
select m;

Ain’t that a beauty? I got this tip from Ron Connery so all the kudos to him.

Create a comma separated list with LINQ in C#

Ola — Tue, 20 Apr 2010 13:29:59 +0000

For some reason I always forget that you do not do .Join on your actual string array. So i might as well write it down here so i never forget about this again.

string mycommalist = string.Join(",", alternatives.Select(x=>x.Item.Name).ToArray())

Group By with LINQ

Ola — Mon, 24 Nov 2008 12:16:58 +0000

Today i wanted to do a group by query with LINQ wich is something i never done before. I turned out to be kind of easy.

If you just want to group by a single field.

(from s in db.CrewStatsSet
where s.LogDate >= date1 && s.LogDate <= date2 && s.Action == action
group s by s.User.nick into g
orderby g.Count() descending
select new CrewStatsData
{
Nick = g.Key,
Count = g.Count(),
}).ToList();

And if you need to group by multiple fields.

(from s in db.CrewStatsSet
where s.LogDate >= date1 && s.LogDate <= date2 && s.Action == action
group s by new { s.User.nick, s.Action, s.User.userID } into g
orderby g.Count() descending
select new CrewStatsData
{
Nick = g.Key.nick,
Count = g.Count(),
ActionId = g.Key.Action,
UserId = g.Key.userID
}).ToList();

Create a tag cloud with limited amout of tags in ASP.NET and LINQ

Ola — Tue, 14 Oct 2008 15:13:12 +0000

Today i built a Tag cloud for my new site. I found this great article about on how to do it with LINQ and C#. But i missed some features. Especially how to limit the number of tags that was shown. So if you read that article and then have a look at this code if you have the same problem as me.

var tagSummary = (from ti in db.TagItemRelations
group ti by ti.Tag.Text into tagGroup
select new {
Tag = tagGroup.Key,
TagFrequency = tagGroup.Count()
}).OrderByDescending(x=>x.TagFrequency).Take(20);

int maxTagFrequency = (from t in tagSummary select t.TagFrequency).Max();

var tagCloud = (from ti in tagSummary
select new TagCloudItem {
Tag = ti.Tag,
Weight = (double)ti.TagFrequency / maxTagFrequency * 100
}).OrderBy(x=>x.Tag);

The main difference between my code and the code in the article is that i have slightly more complex data model (should not matter) and that i make the second query against the “result” from the first query. This allow me to first order by popularity and then in alphabetic order.

Please leave a comment if there is any better way to do this or if you have any questions.