[SalesForce] Create a file using .NET toolkit

Is there a way to create a file using the .NET toolkit ?

I can't find it when configuring my data services in visual studio 2015.

I found Attachment and Document but I heard Attachment will be deprecated soon and Document can't be directly linked to an opportunity.

Below is the code I use today :

public bool AttachProjectDocuments(string siren, string description, IEnumerable<DocumentWithDataDto> projectDocuments)
    {
        var account = Query<Account>("SELECT ID FROM Account WHERE SIREN__c = " + siren);
        if (account != null && account.Records.Any())
        {
            var opportunity = Query<Opportunity>("SELECT ID, Name, CreatedDate, eligibility_rating__c, loan_duration_request__c, loan_reason__c, Loan_amount_request__c FROM Opportunity WHERE AccountId = '" + account.Records[0].Id + "'");
            if (opportunity != null && opportunity.Records.Any())
            {
                var lastOpportunity = opportunity.Records.OrderByDescending(x => x.CreatedDate).First();

                Update("Opportunity", lastOpportunity.Id,
                       new Opportunity
                       {
                           Id = lastOpportunity.Id,
                           AccountId = account.Records[0].Id,
                           Loan_amount_request__c = lastOpportunity.Loan_amount_request__c,
                           loan_duration_request__c = lastOpportunity.loan_duration_request__c,
                           loan_reason__c = lastOpportunity.loan_reason__c,
                           eligibility_rating__c = lastOpportunity.eligibility_rating__c,
                           LeadSource = lastOpportunity.LeadSource,
                           Loan_request_details__c = description,
                           CloseDate = DateTime.UtcNow,
                           Request_submission__c = DateTime.UtcNow,
                           StageName = "Needs Analysis",
                           Name = lastOpportunity.Name,
                           Year_N_accounts__c = true,
                           Year_N_1_accounts__c = true,
                           Year_N_2_accounts__c = true
                       });
                foreach (var doc in projectDocuments)
                {
                    var attachment = new Attachment
                                     {
                                         ParentId = lastOpportunity.Id,
                                         BodyLength = doc.Data.Length,
                                         Name = doc.Name,
                                         ContentType = doc.MimeType,
                                         Body = doc.Data
                                     };
                    Create("Attachment", attachment);
                }
                return true;
            }
        }
        return false;
    }