使用 C# 制作算法来理解 00/00/00

我正在一个名为Prophet 21的程序中为业务规则编写C#代码。

该代码本质上是说，如果产品价格在去年更新，请将该价格放入名为PO Price的字段中。

除了一个小问题外，一切都很稳定，当确保价格在去年内更新时，它会查看 PO 价格更新日期。 在过去的某个时候，其中很多都设置为 00/00/00，使用带有日期的算法似乎无法理解它。 我最好的猜测是我需要以某种方式转换日期，但我是一个相当 C# 新手，任何帮助将不胜感激。 这是我正在使用的代码。

public class SetPOCost : Rule  //this rule sets the PO cost to the other cost when the item is stockable and the disposition is B
{
    public override RuleResult Execute()
    {
        RuleResult result = new RuleResult();
        result.Success = true;
        string s = Data.Fields["other_cost"].FieldValue;
        decimal ldcOtherCost = Convert.ToDecimal(s);
        s = Data.Fields["po_cost"].FieldValue;
        decimal ldcPOCost = Convert.ToDecimal(s);
        string stockable = Data.Fields["stockable"].FieldValue;
        string disposition = Data.Fields["disposition"].FieldValue;
        s = Data.Fields["ufc_inventory_supplier_date_cost_last_modified"].FieldValue;
        //this next line is added from the SuggestPromiseDate rule because it was running into errors doing both rules
        Data.Fields.GetFieldByAlias("suggested_promise_date").FieldValue = Data.Fields.GetFieldByAlias("line_max_promise_date").FieldValue;
        DateTime dtLastModified = Convert.ToDateTime(s);
        DateTime thisDate = DateTime.Today;
        DateTime thisDateLastYear = thisDate.AddYears(-1);
        Boolean dateIsGood = dtLastModified.CompareTo(thisDateLastYear) >= 0;
        if (stockable == "N" && disposition == "B" && ldcPOCost == 0 && ldcOtherCost > 0 && dateIsGood)
        {
            Data.Fields["po_cost"].FieldValue = ldcOtherCost.ToString();
        }
        return result;
    }

s = Data.Fields["ufc_inventory_supplier_date_cost_last_modified"].FieldValue;
//this next line is added from the SuggestPromiseDate rule because it was running into errors doing both rules
Data.Fields.GetFieldByAlias("suggested_promise_date").FieldValue = Data.Fields.GetFieldByAlias("line_max_promise_date").FieldValue;
DateTime dtLastModified;
if (DateTime.TryParse(s, out dtLastModified) == false)
    dtLastModified = DateTime.MinValue;

s = Data.Fields["ufc_inventory_supplier_date_cost_last_modified"].FieldValue;
if (s == "00/00/00") {
    s="01/01/0001";
}