C# 执行EF SaveChanges时处理重复记录

我有一个web应用程序，我在其中解析一个csv文件，该文件中可以有超过200000条记录。我解析每一行的信息，验证数据库中不存在密钥，然后将其添加到上下文中。当计数达到10000条记录时，它调用SaveChanges例程。问题是上下文中可能存在重复项，并且会出错。这是在与Azure SQL server通信的Azure VM上运行的

两个问题，我如何处理重复的问题，有什么方法可以提高速度，因为它需要几个小时才能运行

            using (LoanFileEntities db = new LoanFileEntities())
            {
                db.Configuration.AutoDetectChangesEnabled = false; // 1. this is a huge time saver
                db.Configuration.ValidateOnSaveEnabled = false;  // 2. this can also save time

                while (parser.Read())
                {
                    counter++;

                    int loan_code = 0;
                    string loan_code_string = parser["LoanId"];

                    string dateToParse = parser["PullDate"].Trim();
                    DateTime date_pulled;
                    try
                    {
                        date_pulled = DateTime.Parse(dateToParse, CultureInfo.InvariantCulture);
                    }
                    catch (Exception)
                    {
                        throw new Exception("No Pull Date for line " + counter);
                    }

                    string originationdate = parser["OriginationDate"].Trim();
                    DateTime date_originated;
                    try
                    {
                        date_originated = DateTime.Parse(originationdate, CultureInfo.InvariantCulture);
                    }
                    catch (Exception)
                    {
                        throw new Exception("No Origination Date for line " + counter);
                    }

                    dateToParse = parser["DueDate"].Trim();
                    DateTime date_due;
                    try
                    {
                        date_due = DateTime.Parse(dateToParse, CultureInfo.InvariantCulture);
                    }
                    catch (Exception)
                    {
                        throw new Exception("No Due Date for line " + counter);
                    }

                    string region = parser["Region"].Trim();

                    string source = parser["Channel"].Trim();

                    string password = parser["FilePass"].Trim();

                    decimal principalAmt = Convert.ToDecimal(parser["Principal"].Trim());

                    decimal totalDue = Convert.ToDecimal(parser["TotalDue"].Trim());

                    string vitaLoanId = parser["VitaLoanId"];

                    var toAdd =
                        db.dfc_LoanRecords.Any(
                            x => x.loan_code_string == loan_code_string);
                    if (!toAdd)
                    {
                        dfc_LoanRecords loan = new dfc_LoanRecords();
                        loan.loan_code = loan_code;
                        loan.loan_code_string = loan_code_string;
                        loan.loan_principal_amt = principalAmt;
                        loan.loan_due_date = date_due;
                        loan.date_pulled = date_pulled;
                        loan.date_originated = date_originated;
                        loan.region = region;
                        loan.source = source;
                        loan.password = password;
                        loan.loan_amt_due = totalDue;
                        loan.vitaLoanId = vitaLoanId;

                        loan.load_file = fileName;
                        loan.load_date = DateTime.Now;

                        switch (loan.region)
                        {
                            case "UK":
                                if (location.Equals("UK"))
                                {
                                    //db.dfc_LoanRecords.Add(loan);
                                    if (loan.source == "Online")
                                    {
                                        counter_new_uk_online++;
                                    }
                                    else
                                    {
                                        counter_new_uk_retail++;
                                    }
                                }
                                break;
                            case "US":
                                if (location.Equals("US"))
                                {
                                    db.dfc_LoanRecords.Add(loan);
                                    if (loan.source == "Online")
                                    {
                                        counter_new_us_online++;
                                    }
                                    else
                                    {
                                        counter_new_us_retail++;
                                    }
                                }
                                break;
                            case "Canada":
                                if (location.Equals("US"))
                                {
                                    db.dfc_LoanRecords.Add(loan);
                                    if (loan.source == "Online")
                                    {
                                            counter_new_cn_online++;
                                    }
                                    else
                                    {
                                        counter_new_cn_retail++;
                                    }
                                }
                                break;
                        }
                        // delay save to speed up load.   3. also saves transactional time
                        if (counter % 10000 == 0)
                        {
                            db.SaveChanges();
                        }
                    }

                }  // end of parser read
                db.SaveChanges();
            }
        }
    }

---

我建议在将代码发送到.SaveChanges（）之前删除代码中的重复项

我没有详细讨论重复删除，而是列出了有关StackOverflow的现有问题和答案的链接列表，这些链接可能会有所帮助：

希望有帮助