Validate the date format in vb.net - vb.net

Question

I have the grid cell value to validate for a correct format as below
Date value should be in DD-MON-YYYY format and for this i am using below validation
Public Function ValidateDateForError(ByVal checkInputValue As String) As Boolean
Dim returnError As Boolean
Dim dateVal As DateTime
If Date.TryParseExact(checkInputValue, "DD-MON-YYYY",
System.Globalization.CultureInfo.CurrentCulture,
DateTimeStyles.None, dateVal) Then
returnError = True
Else
MessageBox.Show("not converted")
End If
Return returnError
End Function`
DateTime value should be in DD-MON-YYYY HH:MI:SS format and for this i am using below validation
Public Function ValidateDateTimeForError(ByVal checkInputValue As String) As Boolean
Dim returnError As Boolean
Dim dateVal As DateTime
If DateTime.TryParseExact(checkInputValue, "DD-MON-YYYY HH:MI:SS",
System.Globalization.CultureInfo.CurrentCulture,
DateTimeStyles.None, dateVal) Then
returnError = True
End If
Return returnError
End Function`
EDate (valid European date) value should be in DD/MM/YY format and for this i am using below validation
Public Function ValidateEDateForError(ByVal checkInputValue As String) As Boolean
Dim returnError As Boolean
Dim dateVal As Date
If Date.TryParseExact(checkInputValue, "DD/MM/YY",
System.Globalization.CultureInfo.CurrentCulture,
DateTimeStyles.None, dateVal) Then
returnError = True
End If
Return returnError
End Function`
JDate (valid Julian date) value should be in MM/DD/YY format and for this i am using below validation
Public Function ValidateJDateForError(ByVal checkInputValue As String) As Boolean
Dim returnError As Boolean
Dim dateVal As Date
If Date.TryParseExact(checkInputValue, "MM/DD/YY",
System.Globalization.CultureInfo.CurrentCulture,
DateTimeStyles.None, dateVal) Then
returnError = True
End If
Return returnError
End Function`
but none of above is working. could anyone tell me where i am making mistake?
Thanks in Advance.

Answer 1

Using ParseExact means that you will be telling it the precise format the string will be in. These are case sensitive to allow things like H vs h for 12/24 clock and MM vs mm to distinguish Month from Minutes. So, "DD-MON-YYYY" is invalid, "dd-MM-yyyy" may be what you are after.
But, this means the user would always have to enter 2 digits for the day and month as in "19-07-2014" or "04-07-2014" which they are often not inclined to do, and seems harsh to impose. TryParseExact will take an array of formats so you can be flexible:
Dim strFoo As String = "19-7-2014" ' d-MM-yyyy
Dim strBar As String = "19-07-2014" ' dd-MM-yyyy
Dim strJuly4 As String = "4-7-2014" ' d-M-yyyy
' several possible format styles
Dim formats() As String = {"d-MM-yyyy", "dd-MM-yyyy",
"dd-M-yyyy", "d-M-yyyy"}
Dim thisDt As DateTime
' this should work with all 3 strings above
If DateTime.TryParseExact(strFoo, formats,
Globalization.CultureInfo.InvariantCulture,
DateTimeStyles.None, thisDt) Then
Console.WriteLine("Success! {0}", thisDt.ToString)
End If
Most of the time there it is silly to force them to enter "04" for a month or day and d/M/yyyy will work with strings with the leading "0" (but not the reverse!). Its is added here mainly to show how to pass an array of format patterns.
DO consult MSDN for the proper Standard Date and Time Format Strings
As for Julian Dates, one form of them is to use the form yyDDD to denote the 2 digit year and day of year for the last 3 digits. I dont know if the convention for this changed after 1/1/2000 when all Julian for this Century would sort below those for the 1990s. Still, here is how it is done:
Dim jdt As DateTime = #2/11/2010#
Dim jdate As String = xdt.Year.ToString & xdt.DayOfYear.ToString("000")
' ===> '2010042 or 42nd day of 2010
jdate = (xdt.Year - 2000).ToString("00") & xdt.DayOfYear.ToString("000")
' ===> '10042 or 42nd day of 2010