Search for multiple keywords using LINQ vb - asp.net

Question

I have some existing code that I need to modify to search more than one keyword. (I am new to all this by the way)
Dim topics As IQueryable(Of Global.Platform.Core.Data.Topic) = _
From t In _db.Topics
Where t.IsActive = True And t.TopicTitle.Contains(criteria) And t.ForumID = 0 And Not t.TopicTitle.Contains("default") And t.Member.IsActive = True And t.IsActive = True
Order By t.DateCreated Descending
Select t
Take (take_x)
Return topics
How would i go about changing this so if I entered criteria "cat hair" it would do an OR search. so ...t.TopicTitle.Contains("cat") OR t.TopicTitle.Contains("hair") ....
Of course it would need to be dynamic.
I tried this but could not get it to work.
Dim criteriaArr As Array = criteria.Split(" ")
Dim new_criteria As String = " t.TopicTitle.Contains(" + criteriaArr(0) + ")"
If criteriaArr.Length > 1 Then
For Each item As String In criteriaArr
new_criteria += " Or t.TopicTitle.Contains(" + item + ")"
Next
End If
The idea was to split the spaces and keep appending to the where clause. I know in SQL this might have worked, but how would I go about in this scenario?

Answer 1

You can use a combination of .Any and .Contains:
var strings = new List<string> { "cat", "dog", "bill" };
using (var context = new MyEntities())
{
var matches = context.MyObject.Where(x => strings.Any(s => x.TopicTitle.Contains(s)));
}
VB:
Dim strings = {"cat", "dog", "bill"}
Using context = New MyEntities()
Dim matches = context.MyObject.Where(Function(x) strings.Any(Function(s) x.TopicTitle.Contains(s)))
End Using
This is taking the strings list of query words, and checking to see if there are any of them that the TopicTitle contains.
Sorry, that's in C#, but you can see how to do the lamda expression in the .Where. Just send in a List to your method that does the query, and you're good to go.

Answer 2

Assuming TopicTitle and the criteria are space delimited strings I would intersect the two collections and check if there were any matches.
Dim topics As IQueryable(Of Global.Platform.Core.Data.Topic) = _
From t In _db.Topics
Where t.IsActive = True And t.TopicTitle.Intersect(criteria).Any()
And t.ForumID = 0 And Not t.TopicTitle.Contains("default")
And t.Member.IsActive = True And t.IsActive = True
Order By t.DateCreated Descending
Select t
Take (take_x)
Return topics