Unable cast <TakeIterator>d__3a`1[System.Object] to type System.Collections.Generic.IEnumerable

Question

I have a process to read a CSV file to database. This csv is over 600 Mb so I can't set all in memory. I use generic pattern to achieve this but I have problems on casting:

Here I Read the file

using (var fs = File.OpenText(Path.Combine(FolderContainer, filename)))
{
    var csvConfiguration = new CsvConfiguration
    {
        HasHeaderRecord = true,
        Delimiter = ","
    };
    using (var csvReader = new CsvReader(fs, csvConfiguration))
    {
        csvReader.Configuration.RegisterClassMap(CsvMapping.CsvMapping.RetrieveMapType(type));
        var list = csvReader.GetRecords(type);
//            Console.WriteLine(list.First());
        dynamic repository = Activator.CreateInstance(typeof(Repository<>).MakeGenericType(type), UnitOfWork);
//            var activities = new Repository<Activity>(UnitOfWork);
        repository.InsertAllOnSubmit(list.Take(100));
        repository.SubmitChanges();
    }
}

I use the Take(100) for my tests purpose, I use a Unit of work InMemory.

Here is the Repository method called

public void InsertAllOnSubmit(IEnumerable<T> entities)
{
    _source.InsertAllOnSubmit(entities);
}

public void InsertAllOnSubmit(IEnumerable<object> entities)
{
//        foreach (var entity in entities)
//        {
//            InsertOnSubmit((T) entity);
//        }
    this.InsertAllOnSubmit((IEnumerable<T>)entities);
}

When I execute my test, I have a castException

System.InvalidCastException : Unable to cast object of type '<TakeIterator>d__3a`1[System.Object]' to type 'System.Collections.Generic.IEnumerable`1[KboOpenDataData.Activity]'.

I Try to add a AsEnumerable() or a ToList() after the Take(100) as readed on http://blog.codelab.co.nz/2009/12/22/unable-to-cast-object-of-type-issue/ with no success. And I don't want to use ToList because I can't set the whole file in memory due to size.

I comment the lines where I used a foreach in the repository class, the foreach works but it's very very slow.

Any advices to success the cast?

Answer 1

Try following -

repository.InsertAllOnSubmit(list.Take(100).Cast<Activity>());

Cast extension method lets you cast enumerables from one type to another (Assuming of course that the cast is valid.. which is what you expect with explicit casts).