使用LINQ vb搜索多个关键字

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