Creating function to query with linq in a MongoDB Singleton

Working with Data Drivers
,
1

I’m creating a singleton class to query mongo collections in a .Net 6 web api. Since my application will query several different collections in 3 different databases so I’m making a function that receives the names of the collection and database together with the query parameters.

public class MongoReader
{
    private MongoClient _client;
    
    public MongoReader(string connectionString)
    {
        ConventionPack pack = new ConventionPack();
        pack.Add(new IgnoreExtraElementsConvention(true));
        ConventionRegistry.Register("My Solution Conventions", pack, t => true);

        _client = new MongoClient(connectionString);
    }
    
    public async Task<List<T>> QueryCollection<T>(string collection, FilterDefinition<T> filter,int limit = 50,int batchSize = 50) where T : class 
    {
        string[] collectionInformation = collection.Split('.');
        string collectionName = collectionInformation[1];
        string collectionDatabase = collectionInformation[0];

        List<T> list = new List<T> ();

        FindOptions<T> findOptions = new FindOptions<T>() { Limit = limit , BatchSize = batchSize };

        IAsyncCursor<T> cursor = await _client.GetDatabase(collectionDatabase).GetCollection<T>(collectionName).FindAsync(filter, findOptions);

        list = await cursor.ToListAsync();

        return list;
    }
}

The current class only has a function with FilterDefinition as parameter but I also wish for a similar function that would allow me to use Linq as an argument. How can i do that?

This is how I wish to call the function :

MongoReader _reader = new MongoReader("connectionstring");
int limit = 50;
int batchSize = 50;
List<RandomClass> list = await _reader.QueryCollectionLinqAsync<RandomClass>("DatabaseName.CollectionName", t => t.fieldName == fieldValue,limit ,batchSize );

This is what I’m trying to do , currently not working because Where() doesn’t accept FindOptions and doesn’t have ToListAsync() :

public async Task<List<T>> QueryCollection<T>(string collection, Func<T,bool> predicate, int limit = 50, int batchSize = 50) where T : class 
 {
     string[] collectionInformation = collection.Split('.');
     string collectionName = collectionInformation[1];
     string collectionDatabase = collectionInformation[0];

     List<T> list = new List<T>();

     FindOptions<T> findOptions = new FindOptions<T>() { Limit = limit, BatchSize = limit };

     return await _client.GetDatabase(collectionDatabase).GetCollection<T>(collectionName).AsQueryable().Where(predicate,findOptions ).ToListAsync();
 }
2

I failed to find the edit button so I will write here the change that I made.
I found out that when using AsQueryable(), it’s used an aggregate so I need to used AggregateOptions instead of FindOptions. Now the issue is only the fact that Where() does not have ToListAsync(), only ToList() so how can I make this async? And yes, I’m using MongoDB.Driver.Linq namespace.

Here the currrent not working function :

public async Task<List<T>> QueryCollection<T>(string collection, Func<T,bool> predicate, int limit = 50, int batchSize = 50) where T : class 
{
    string[] collectionInformation = collection.Split('.');
    string collectionName = collectionInformation[1];
    string collectionDatabase = collectionInformation[0];

    List<T> list = new List<T>();

    AggregateOptions options = new AggregateOptions() { BatchSize = batchSize };

    return await _client.GetDatabase(collectionDatabase).GetCollection<T>(collectionName).AsQueryable(options).Where(predicate).Take(limit).ToListAsync();
}