如何验证下拉列表 [英] how to validate the dropdown list

问题描述

我有下拉列表如下





批量开始日期Dropdownlist1（日期）Dropdownlist2（月份）Dropdownlist3（年份）



发行日期Dropdownlist4（日期）Dropdownlist5（月）Dropdownlist6（年）







String startdate;

DateTime Batchstartdate;



startdate = this.Dropdownlist1.Text.ToString（） .Trim（）+ - + this.Dropdownlist2.Text.ToString（）。Trim（）+ - + this.Dropdownlist3.Text.ToString（）。Trim（）;

Batchstartdate = Convert.ToDateTime（startdate.ToString（））;



string issuedate;

DateTime Batchissuedate;



issuedate = this.Dropdownlist4.Text.ToString（）。Trim（）+ - + this.Dropdownlist5.Text.ToString（）。Trim（）+ - + this.Dropdownlist6。 Text.ToString（）。Trim（）;

Batchissuedate = Convert.ToDateTime（issuedate.ToString （））;





i想验证发行日期不小于开始日期。



为什么我可以使用csharp进行验证。





if（startdate.ToString（）< issate.ToString（））

{

Label23.Text =开始日期必须大于发行日期;

return;

}



当我运行时显示错误如下

运算符'<'不能应用于操作数输入'string'和'string'





我怎么能用cshrp做什么。



请帮帮我。



问候，

Narasiman P.

i have dropdownlist as follows


Batch start date Dropdownlist1(Date) Dropdownlist2(month) Dropdownlist3(year)

Issue date Dropdownlist4(Date) Dropdownlist5(month) Dropdownlist6(year)



String startdate;
DateTime Batchstartdate;

startdate = this.Dropdownlist1.Text.ToString().Trim() + "-" + this.Dropdownlist2.Text.ToString().Trim() + "-" + this.Dropdownlist3.Text.ToString().Trim();
Batchstartdate = Convert.ToDateTime(startdate.ToString());

string issuedate;
DateTime Batchissuedate;

issuedate = this.Dropdownlist4.Text.ToString().Trim() + "-" + this.Dropdownlist5.Text.ToString().Trim() + "-" + this.Dropdownlist6.Text.ToString().Trim();
Batchissuedate = Convert.ToDateTime(issuedate.ToString());


i want to validate issue date is not less than start date.

for that how can i validate using csharp.


if (startdate.ToString() < issuedate.ToString())
{
Label23.Text = "Start Date must be greater than the Issue date";
return;
}

when i run shows error as follows
Operator '<' cannot be applied to operands of type 'string' and 'string'


for that how can i do using cshrp.

Please help me.

Regards,
Narasiman P.

推荐答案

你可以使用< DateTime本身的运算符：

Hi, you can use the < operator on DateTime itself:

if (startdate < issuedate)
 {
 Label23.Text = "Start Date must be greater than the Issue date";
 return;
 }

查看 DateTime.Compare 方法。



然后你可以这样做：

Have a look at the DateTime.Compare method.

Then you could do something like:

if(DateTime.Compare(Batchissuedate, Batchstartdate)>0)
{
    Label23.Text = "Start Date must be greater than the Issue date";
}

在你的代码中，startdate和authorate是两个字符串所以我们比较这两个日期，所以比较你的



Batchstartdate和Batchissuedate。



if（Batchstartdate< batchissuedate）>

{

Hi,

In your code startdate and issuedate are two strings so we compare those two dates so compare your

Batchstartdate and Batchissuedate.

if(Batchstartdate <batchissuedate)>
{

Label23.Text = "Start Date must be greater than the Issue date";

}

}

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