我有一个Web服务器运行了两年（SQL Server 2017和ASP.NET Web表单）
但这两天出现了重复插入数据。
插入数据前查找数据，检查数据是否为非空，是否为重复数据中的SQL server。
然而，我无法找出解决这个问题的最佳做法。

工具箱.cs#

public string getID(string PId, string TestId)
    {
        string idCode = "";
        char FillUp = '0';
        int length = 4;
        int one = 0;

        if (PId.Length != 10)
        {
            throw new NullReferenceException("Error");

        }
        string newId = PId.Replace("-", "");
        if (TestId == null)
        {
            idCode = newId + "0001";
        }
        else
        {
            string checkID = TestId.Substring(11, 4);
            int trynumber;
            int.TryParse(checkID , out trynumber);

            int firstNumber = trynumber + 1;
            string number = firstNumber.ToString();

            string idNumber = number.PadLeft(length, FillUp);
            idCode = newId + idNumber;

        }

        return idCode;

    }

添加数据.ashx

using (Entity EntityData= new Entity())
            {
       var checkID = EntityData.TEST_DATA.AsNoTracking()
                    .Where(o => o.NUMBER_NO == XXXX_NO)
                    .OrderByDescending(o => o.ID)
                    .FirstOrDefault();

                toolbox tool = new toolbox();

                if (checkID == null)
                {
                    ID = tool.getID(getPID, null);
                }
                else
                {
                    ID = tool.getID(getPID, checkID.ID);
                }

                TEST_DATA addDATA = new TEST_DATA();
                addDATA.ID = ID;
                addDATA.NUMBER_NO = XXXX_NO;

                addDATA.RECDATE = DateTime.Now;
                addDATA.MODIFY_TIME = DateTime.Now;

                EntityData.TEST_DATA.Add(addDATA);
                EntityData.SaveChanges();
}