How to use Linq and the IN clause

Question

Here is my code

if (catid != 0)
            posts = posts.Where(x => x.catid IN '1,8,2,109,23');

The in in this code shows as a syntax error. Is there a way to fix this

Answer 1

You must use another list to compare too.

List<int> cadIdFoundList = new List<int>();

cadIdFoundList.Add(1);
cadIdFoundList.Add(8);
// etc. . . 

posts.Where(x => cadIdFoundList.Contains(x.catId));

Answer 2

int[] ids = new int[] { 1, 8, 2, 109, 23 };
var query = posts.Where(x => ids.Contains(x.catid));

Rob Conery has discussed this topic before.

Answer 3

Or even more simple:

var query = posts.Where(x => new[] { 1, 8, 2, 109, 23 }.Contains(x.catid));

Answer 4

Maybe something more like:

HashSet<int> categories = new HashSet<int>() { 1, 2, 8, 23, 109};
posts = posts.Where(post => categories.Contains(post.catid));