How do I use LINQ Contains(string[]) instead of Contains(string)

SpoiledTechie.com picture SpoiledTechie.com · Oct 12, 2008 · Viewed 410.8k times · Source

I got one big question.

I got a linq query to put it simply looks like this:

from xx in table
where xx.uid.ToString().Contains(string[])
select xx

The values of the string[] array would be numbers like (1,45,20,10,etc...)

the Default for .Contains is .Contains(string).

I need it to do this instead: .Contains(string[])...

EDIT : One user suggested writing an extension class for string[]. I would like to learn how, but any one willing to point me in the right direction?

EDIT : The uid would also be a number. That's why it is converted to a string.

Help anyone?

Answer

tvanfosson picture tvanfosson · Oct 12, 2008

spoulson has it nearly right, but you need to create a List<string> from string[] first. Actually a List<int> would be better if uid is also int. List<T> supports Contains(). Doing uid.ToString().Contains(string[]) would imply that the uid as a string contains all of the values of the array as a substring??? Even if you did write the extension method the sense of it would be wrong.

[EDIT]

Unless you changed it around and wrote it for string[] as Mitch Wheat demonstrates, then you'd just be able to skip the conversion step.

[ENDEDIT]

Here is what you want, if you don't do the extension method (unless you already have the collection of potential uids as ints -- then just use List<int>() instead). This uses the chained method syntax, which I think is cleaner, and does the conversion to int to ensure that the query can be used with more providers.

var uids = arrayofuids.Select(id => int.Parse(id)).ToList();

var selected = table.Where(t => uids.Contains(t.uid));