CODEWITHSUNDEEP
c#linq
user971210
user971210

Reputation: 21

Linq - Query a query result agains a list of strings

I have a list of strings

List<string> firstNames = new List<string>();

I have a query result 

var contacts = (from p in datacontext.Contact)

How Can I Query the original result (contacts) against the list of strings?

select * from contacts where contacts.firstname like firstNames

something like 

firstNames.Any(x=>x.contacts.Contains(x))

Upvotes: 2

Views: 1859

Answers (2)

Ricketts
Ricketts

Reputation: 5223

First, visit this link, download the class and add it to your App_Code folder: http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx

Then be sure to add "using System.Linq.Dynamic;"

Then construct your query like this:

    DatabaseDataContext db = new DatabaseDataContext();
    List<string> firstNames = new List<string>();

    //--- loop through names and build a where query
    string WhereClause = string.Empty;
    for (int i = 0; i < firstNames.Count(); i++)
    {
        string s = firstNames[i].ToLower();

        if (i != Communities.Length - 1)
            WhereClause += "FirstName.ToLower().Contains(\"" + s + "\") OR "; //--- first name is the field name in the db
        else
            WhereClause += "FirstName.ToLower().Contains(\"" + s + "\")";
    }

    //--- execute query and pass the dynamic where clause
    IQueryable contacts = db.Contacts
                          .Where(WhereClause)
                          .OrderBy("FirstName");

Good Luck!

Upvotes: 0

Jon Skeet
Jon Skeet

Reputation: 1503869

You should probably push the first names into the database query, like this:

var contacts = dataContext.Contacts.Where(c => firstNames.Contains(c.FirstName));

Now you used "like" in your sample query, so maybe you want:

var contacts = dataContext.Contacts
                     .Where(c => firstNames.Any(f => c.FirstName.Contains(f)));

If you could provide some concrete examples it would help.

EDIT: If you're really pulling back all the contacts from the database already into (say) a List<Contact> contacts, then you could use:

var matchingContacts = from contact in contacts
                       join name in firstNames
                       on contact.FirstName equals name
                       select contact;

Upvotes: 3

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