Question 265107 in Mongodb Question posted in
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Missing async methods in MongoDB.Driver 2.22.0

I’m working on integrating MongoDB / LINQ with my codebase, and I keep reading about these FirstOrDefaultAsync or ToListAsync() methods from the MongoDb Driver. However, I don’t have those available. Am I missing some NuGet package that everyone else uses? I’m on .net 7.0.

using Mangler.Common.Functions;
using ManglerAPI.Infrastructure.Mongo;
using ManglerAPI.Stories.Entities;
using MongoDB.Driver.Linq;
using MongoDB.Driver;

namespace ManglerAPI.Stories.Repositories;

public interface IStoryRepository
{
    Task<OperationResult<Story>> GetById(long id);
}


public class StoryMongoRepository : IStoryRepository
{
    private readonly IQueryable<Story> _stories;

    public StoryMongoRepository(MongoClientFactory clientFactory)
    {
        _stories = clientFactory.GetClient<Story>("Stories");
    }
 
    public async Task<OperationResult<Story>> GetById(long id)
    {
        // FirstOrDefault does not exist.
        var data = await _stories.FirstOrDefaultAsync();
            
        return data is null ? 
            OperationResult<Story>.Failure(ResultCode.EntityNotFound) : 
            OperationResult<Story>.Success(data);
    }
}
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2

Answers


  1. 0

    The problem was the IQueryable<T> is from the System.Linq which doesn’t have the FirstOrDefaultAsync and ToListAsync extension method.

    Instead, you should use the IMongoQueryable<T> from MongoDB.Driver.Linq.

    private readonly IMongoQueryable<Story> _stories;

    And you need to modify

    using MongoDB.Driver.Linq;

public class MongoClientFactory
{
    public IMongoQueryable<T> GetClient<T>(string collectionName)
    {
        MongoClient client = /* Mongo Client instance */
        IMongoDatabase db = client.GetDatabase(/* Your database */);

        return db.GetCollection<T>(collectionName).AsQueryable();
    }
}
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  2. 0

    These async methods are extensions for IMongoQueryable, not IQueryable (which is a base interface for IMongoQueryable). So you should work with the interface that is provided for you by AsQueryable method, ie with IMongoQueryable

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