CODEWITHSUNDEEP
linqentity-framework
DenaliHardtail
DenaliHardtail

Reputation: 28306

How do I select a person only if their Id appears in another table?

In the following LINQ statement, I'm trying to select people but only if their Id appears in another table (a join table). What am I missing?

In this example, I have a People table and a Contractors table. The Person's contactId may appear in the Contractors table. I want to grab the contactId of People that appear in the Contractors table.

var allPeople = People.Where(x => x.Contractors
                                   .Where(m=> m.ContactID == x.ContactID)
                                  .Select(x => x.ContactID));

Upvotes: 0

Views: 553

Answers (2)

Schultz9999
Schultz9999

Reputation: 8926

How about regular LINQ JOIN statement:

var peopleWithContact = People.Join(
    Contractors, 
    p => p.ContactId, // the field to join by from People table
    c => c.ContactId, // the field to join by from Contractors table
    (p, c) => p.ContactId); // the result if match; could be just p.

Upvotes: 1

Jakob
Jakob

Reputation: 24360

The Where function must return a boolean expression. If I understand your question correctly, you only want people from the peoples table that are in the contractors table as well. Then we can ask just that: Give me a person if any contractor has that ID:

var allPeople = People.Where(x => x.Contractors
                                   .Any(m => m.ContactID == x.ContactID));

Upvotes: 0

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