MongoDB C# Check if a string contains a field in Expression Query

Question

With the following model

public class Product{
    [BsonId][BsonRepresentation{BsonType.ObjectId}]
    public string Id {get; set;}
    public string ItemName {get; set;}
}

I want to write the following query:

var items = Db.Products.Find(x => SearchText.Contains(x.ItemName)).ToList();

But mongodDB gives me an error saying the query is invalid and that I can't do String.Contains(x.Field)

So how can I check if a field is contained within a string using MongoDB.Driver library

First of all, this kills the performance. The database engine now has to load all your records and do a partial match. Fulltext search exists for a reason; build an index on index time, do not scan at runtime. You can do a regex search though. — CodeCaster
– CodeCaster, Commented Nov 17, 2021 at 14:32

athagiorgos · Accepted Answer · 2022-09-21 07:58:50Z

1

An easy way to do this is with regular expressions. You can try

var filterFirstName = Builders<Customer>.Filter.Regex("FirstName", "^" + query + ".*");

If you want the results to be combined, then after applying the 2 filters, you can do like

var finalFilter = filterFirstName & filterLastName

finalFIlter has the combined results.

answered Sep 21, 2022 at 7:58

athagiorgos

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