crud-ops.cs

public virtual async Task<IEnumerable<TEntity>> GetByFieldAsync(string field, string value)
{
    var filter = Builders<TEntity>.Filter.Eq(field, value);
    var result = await Collection.Find(filter).ToListAsync();

    return result;
}

public virtual async Task<TEntity> GetByIdAsync(ObjectId id)
{
    var filter = Builders<TEntity>.Filter.Eq("_id", id);
    var entity = await Collection.Find(filter).FirstOrDefaultAsync();

    return entity;
}

public virtual async Task<long> DeleteAllAsync()
{
    var filter = new BsonDocument();
    var result = await Collection.DeleteManyAsync(filter);
    return result.DeletedCount;
}

public virtual async Task<bool> UpdateAsync(ObjectId id, string field, string value)
{
    var update = Builders<TEntity>.Update.Set(field, value);
    var result = await Collection.UpdateOneAsync(u => u.Id == id, update);

    return result.ModifiedCount != 0;
}