how to fix string was not recognized as a valid DateTime

Question

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************** Exception Text **************
System.FormatException: String was not recognized as a valid DateTime.
   at System.DateTimeParse.Parse(String s, DateTimeFormatInfo dtfi, DateTimeStyles styles)
   at System.Convert.ToDateTime(String value)
   at ExtraTutoManager.Dashcont.CulcPay(DateTime dateAf) in D:\coure du soire gestion\visual studio project\ExtraTutoManager\ExtraTutoManage

declaration global


        public DateTime rendVous;
        public DateTime temp;

I want to covert string to datetime by ToDateTime() , in my project VS running without any problem but in another pc this String was not recognized as a valid DateTime

temp = Convert.ToDateTime("" + dateAf.Date.Day + "/" + (DateTime.Now.Month + 1) + "/" + DateTime.Now.Year);

this is my method

        //Culcs
        public DateTime Culcdate(DateTime dateAf)
        {


            int mont = DateTime.Now.Month - dateAf.Date.Month;
            if (DateTime.Now.Month == dateAf.Date.Month)
            {

                temp = Convert.ToDateTime("" + dateAf.Date.Day + "/" + (DateTime.Now.Month + 1) + "/" + DateTime.Now.Year);
            }
            else if (mont - (mont - 1) >= 1 && DateTime.Now.Day >= dateAf.Date.Day)
            {
                temp = Convert.ToDateTime("" + dateAf.Date.Day + "/" + (DateTime.Now.Month + 1) + "/" + DateTime.Now.Year);

            }
            else if (mont - (mont - 1) >= 1)
            {
                temp = Convert.ToDateTime("" + dateAf.Date.Day + "/" + DateTime.Now.Month + "/" + DateTime.Now.Year);

            }

            return rendVous = temp;
        }

What are you trying to achieve? You can add days, month etc. on the DateTime object, why are you working with strings? Your way to do whatever you try to do can easily fail, because you will creat strings which aren't a date (DateTime.Now.Month + 1) will give you a 13th month when one is added to a december date — Developer, Nov 22 '21 at 15:52
Doesn't `(DateTime.Now.Month + 1` be a problem if the month is december? Also what value could be possible for `(mont - (mont - 1) >= 1)`? — Laurent Gabiot, Nov 22 '21 at 15:52

score 4 · Answer 1 · answered Nov 22 '21 at 15:51

4

The reason is failed in other computers is likely to be they have different Cultures, one computer could be trying to parse in American format MM/dd/yyyy and the other one is in dd/MM/yyyy.

You can use DateTime.ParseExact() and specify the format and culture you are trying to parse.

https://learn.microsoft.com/en-us/dotnet/api/system.datetime.parseexact?view=net-6.0

DateTime.ParseExact(temp, "dd/MM/yyyy", CultureInfo.InvariantCulture)

answered Nov 22 '21 at 15:51

Raphael Yoshiga

97
6

Thank you , the problem is exactly as you said, generally the problem has been solved – FLK Coding Nov 22 '21 at 21:18

Fuzzy · Accepted Answer · 2021-11-22T16:08:58.120

Convert.ToDateTime will take into account the current systems Culture and thus expects the string to be in a certain format. See more info here: https://learn.microsoft.com/en-us/dotnet/api/system.convert.todatetime?view=net-6.0#System_Convert_ToDateTime_System_String_System_IFormatProvider_

To make this code work on the other system, you could change the system language used, but a better solution is to make sure that the input value is in the current cultures format, or use the second parameter for Convert.ToDateTime() which is an IFormatProvider to tell the system which culture to use. That way it will not matter anymore what system runs the code.

In your case you could also write:

temp = new DateTime(DateTime.Now.Year, DateTime.Now.Month + 1, dateAf.Date.Day)

instead of

temp = Convert.ToDateTime("" + dateAf.Date.Day + "/" + (DateTime.Now.Month + 1) + "/" + DateTime.Now.Year);

to avoid the date parsing all together. Make sure to not do this when the month is december as that would still result in an invalid datetime.

If you are simply trying to achieve getting the current DateTime + 1 month you could do this:

temp = DateTime.Now.AddMonths(1);

which will also work when the current date is in december, and will result in a date in januari the next year.

thank you , the problem has been solved .. I didn't think the problem was only in the arrangement because the app was working fine in a project VS — FLK Coding, Nov 22 '21 at 21:13

how to fix string was not recognized as a valid DateTime

2 Answers2