Question

Why would dateTimePicker.Value.Date.ToShortDateString(); act differently on Windows 7 x64 PL, Windows Vista x32 PL and Windows XP PL with to my knowledge exact regional settings. I’ve found it out the hard way that i was doing this conversion prior to entering it to DB.

It was working fine on Windows 7 (my development machine), colleague VISTA system but it failed to work on Windows XP (day was switched with month all the time). Also on higher systems we have 2010-01-13 displayed on ListView while on his system he has 13-01-2010.

I imagine in my old code i may have more of those type conversions and i will have to go thru and verify it but i would like to know why it’s behaving that way on same regional settings. I imagine I should never do conversions like that but I’ve learn it the hard way after a long time when it was working fine.

EDIT:

I was using it this way (commented out code that was causing troubles). Back in the old days I thought ToShortDateString was the only way to make sure to put it into DB without Time (since i was reading DateTimePicker). I know now that I should have used .Date on that DateTimePicker but I am smarter now that it did blow up on me. Here’s the code:

    private static void sqlWpiszDaneSwieta(DateTime varData, string varDataNazwa) {
        //string varDataSwieto = varData.ToShortDateString();
        const string preparedCommand = @"INSERT INTO [dbo].[TypyDatySwiat]
                                           ([SwietaData]
                                           ,[SwietaNazwa])
                                     VALUES
                                           (@varData
                                           ,@varDataNazwa)";
          using (var varConnection = Locale.sqlConnectOneTime(Locale.sqlDataConnectionDetails))
        using (SqlCommand sqlWrite = new SqlCommand(preparedCommand, varConnection)) {
            sqlWrite.Prepare();
            sqlWrite.Parameters.AddWithValue("@varData", varData);
            sqlWrite.Parameters.AddWithValue("@varDataNazwa", varDataNazwa);
            try {
                sqlWrite.ExecuteNonQuery();
            } catch (SqlException sqlEx) {
                if (sqlEx.Message.Contains("Violation of PRIMARY KEY constraint")) {
                    MessageBox.Show("Dodanie podanego święta jest niemożliwe. Podane święto istnieje już w bazie danych!", "Bład", MessageBoxButtons.OK, MessageBoxIcon.Error);
                } else {
                    MessageBox.Show(sqlEx.ToString(), "Bład SQL", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
            } catch (Exception ex) {
                MessageBox.Show(ex.ToString(), "Bład", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

So i am not specifically asking for a way to do it. I know how to do it and that i can pass it using DateTime directly to db. Just that i would like to know why would it behave differently on 1 machine.

Answer 1

day was switched with month all the time

That sounds suspiciously like your colleague is using a UK locale on his XP machine, as that is the normal method for a date there.

But I’m more concerned about this:

prior to entering it to DB.

If you’re putting it into a DB, why are you calling .ToShortDateString()? That smells like dynamic sql to me, and that means an sql injection vulnerability. Instead of something like this:

string sql = "INSERT INTO [MyTable] (MyDateColumn) VALUES (" + MyDateVar.ToShortDateString() + ")";
//sql command/connection code omitted from this sample

you need to do something like this:

string sql = "INSERT INTO [MyTable] (MyDateColumn) VALUES (@MyDate)"
using (var cn = new SqlConnection("..connection string.."))
using (var cmd = new SqlCommand(sql, cn))
{
    cmd.Parameters.Add("@MyDate", SqlDbType.DateTime).Value = MydateVar;

//remain code omitted

Notice the latter sample never converts the datetime variable to a string. It will work no matter what locale your users have set.