How To Determine If DateTime Is Not Set
Jan 11, 2010
In VB6 if I wanted to see if a datetime field wasn't set, I could do something like if myDate = 0 then. I tried that with VB.NET and it can't compare to an integer. How do we do this now? I found the Ticks property, so if myDate.Ticks = 0 does seem to work, but I'm not sure if that's the "right" way to do it. None of the other things I've tried have been successful.
Dim dt As New DateTime
If dt.Ticks = 0 Then MsgBox("dt.Ticks = 0") 'this fires
If IsDBNull(dt) Then MsgBox("IsDBNull(dt)") 'doesn't fire, so no good
If Not IsDate(dt) Then MsgBox("Not IsDate(dt)") 'doesn't fire, so no good
'If dt Is Nothing Then MsgBox("dt is nothing") 'not legal syntax
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Oct 22, 2010
The following works fine in c# (assuming value is an object):
if (value is DateTime)
What is the equivalent check for VB.NET?
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Nov 12, 2010
I want to get the date value for
Nov 1, 2010 00:00:00 GMT
expressed in my local time.What is the best way? Currently, I am doing this:
Dim NovGmt As Date = New Date(2010, 11, 1, 0, 0, 0)
Dim Nov1AsLocal As Date = GetGmtExpressedAsLocal(NovGmt)
Private Function GetGmtExpressedAsLocal(ByVal gmtDate As Date) As Date
[code].....
tell me difference between the Date and DateTime datatypes? Is DateTime newer than Date or is it just a synonym for Date? If the latter, why have both?
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Sep 3, 2010
Is there a way in VB.Net to determine if the timezone the current system has daylight savings time in effect? Of course I can get the offset from GMT using the "z"/"zz" formatting option, but that doesn't tell me if DST is in effect for the current timezone or if the current timezone is in standard time...or if DST/Standard time aren't even an issue in the timezone for the system.
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Sep 17, 2011
how to manipulate the dates to determine which date will be 30 days more then the datetime control I have on my form. i need to take the chosen date from the DateTime control, and determine what date it will be in 30 days. Eventually I will use this process to search through the database to print monthly reports.
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Mar 23, 2011
how to convert string to datetime and calculate date
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May 7, 2010
I'm trying to match a certain DateTime value with the current system DateTime. I have a timer and a label on a form. Timer interval is set to 1000. When the form loads, the timer starts ticking. As soon as the current DateTime matches the value of the variable, it shows a message in the label. When I'm writing the following code, the values don't match even if the current system DateTime is equal to the variable. Label1 isn't showing 'Times Matched':[code]The default format of 'Now' is the same as I have stored in dtmVar variable. So there's no question of format mismatch. Does that mean 'Now' is not actually a DateTime property? Provided, my O.S. is Windows Vista Ultimate and all date/time settings are set to default.
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May 1, 2010
I'm trying to match a certain DateTime value with the current system DateTime. I have a timer and a label on a form. Timer interval is set to 1000. When the form loads, the timer starts ticking. As soon as the current DateTime matches the value of the variable, it shows a message in the label.
When I'm writing the following code, the values don't match even if the current system DateTime is equal to the variable. Label1 isn't showing 'Times Matched':
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
Dim dtmNow As DateTime
[Code]....
Why is it so? The default format of 'Now' is the same as I have stored in dtmVar variable. So there's no question of format mismatch. Does that mean 'Now' is not actually a DateTime property? Provided, my O.S. is Windows Vista Ultimate and all date/time settings are set to default.
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Aug 8, 2011
datetime1 and datetime2now two fields are have data ( date )in table recordi want to update only datetime2 is an emptyi am using visual basic 2010 ( visual studio 2010
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Dec 27, 2010
I try to compare Datetime.Now with a Datetime variable I set, using the Datetime.CompareTo() method. I use a timer to compare these every second and display the result, but as the current time approaches the time I set, the result changes from 1 to -1, but never 0, which means these two are never equal. I'm suspecting the Datetime structure contains milliseconds?
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Mar 14, 2011
Assume the following program is started at 1:59:01 AM on 3/13/2011 in the United States. The first time Timer1 ticks what will be the value of the TimeSpan (ts)?
Public Class Form1
Private Sub Timer1_Tick(sender As System.Object, _
e As System.EventArgs) Handles Timer1.Tick
[code].....
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Jan 29, 2011
I'm trying to add the date and time of Today into a Sql-database-field that has the datetype datetime.
[Code]...
the msgbox gives me the following result: 29/01/2011 18:49:21 my sqlException gives me the following error: 102 - Incorrect syntax near '18'. Is it better that i set the datatype to char in my sql database? It's maybe a bit easier? When I do that, can I calculate with these date?
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Oct 27, 2009
How do I convert ISO datetime to locat EST with vb.net?
I have input time as e.g. "20091027T1639Z" which is ISO GMT.
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Jan 12, 2010
[code] "The conversion of a char data type to a datetime data type resulted in an out-of-range datetime value.The statement has been terminated." [code]
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Sep 22, 2008
I'm using VB .NET & SQL Express 2005.I was hoping someone could help me figure this out, I'm trying to search a table between two dates. The table has a datetime column and I am using VS .NET 2005 DateTimePicker control. I'm not getting any errors, but I'm not getting any results either..
[Code]...
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Jun 7, 2011
In my vb.net winform application, I am moving the file from one folder to another. I need to store the datetimevalue when the transfer has been done. Later I need to show this DateTime value in my Grid. Here is the code i have written, but not able to store the datetime value.
[Code]...
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Jun 12, 2012
the last date was saved on database is: 6/13/2012 12:27:30 PM
In my DateTime Now is:6/13/2012 01:27:57 AM
but, when I execute this function, it always say:"Date has been manually modified, Please Set to Valid DateTime" But, DateTime Now is NOT lessthan the Date from my Database. What's wrong?
This is the code, please correct it,
[Code]...
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Mar 31, 2010
I have a DateTime object I want to compare against an sql datetime field in a where clause. I'm currently using:
"where (convert( dateTime, '" & datetimeVariable.ToString & "',103) <= DatetimeField)"
But I believe datetimeVariable.ToString will return a different value depending on the culture where the system is running.
How would you handle this so it is culture independent?
EDIT : I won't be using paramatised sql in this code...
EDIT : following Parmesan's comment to one of the answers looks like the best method may be:
"where (convert( dateTime, '" & datetimeVariable.ToString( "s" ) & "',126) <= DatetimeField)"
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Mar 2, 2012
[Code]in my program, i've created a function wherein i will get the min timeentry for type 0 and it depends on the current date. so heres how it goes [Code] what should i put as the value of time entry? i tried format(var,"m") but no success. in the code i post above it also does not work. i get this error "The conversion of a varchar data type to a datetime data type resulted in an out-of-range value." how can i match the value in the database and the current date so that i can retrieve a value?
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Sep 6, 2010
i have a datatable in access with a column " Time " and i use it in a datagridview how can i format it to short time in dgv
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May 6, 2009
My SQL server is running from the west coast and I live in the east coast, I am running a VB.NET code and to check for items within the right time I have to use DateTime.Now.AddHours(-3).
Now thinking about it, when the daylight savings happen, it will only be DateTime.Now.AddHours(-2), how do I go about fixing that from now? Is there a way to fix that?
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Sep 19, 2010
here i;m trying to select a date and time but i'm having problems can you see what i'm doing wrong Dim table = mydataset.Tables("Bookingen")
[Code]...
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Mar 31, 2011
Could someone tell me what is wrong with this code
Public Shared Function TestDateTime() As String
Dim Result As String = ""
Dim Test As DateTime
[code].....
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Jun 23, 2011
How can I get the difference of this two Date time.
(6/21/2011 7:02:53 AM) subtract by (6/21/2011 4:00:00 AM)
the answer should be ---> 03:02:53
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Oct 5, 2010
I've hit a snag in one of my apps and I could code it differently so it would work, but I'd rather figure out why its not working as is.
If you add a watch in VS to dtDate.Tobinary and lDateInBinary you will see they do not hold the same number; however, it evaluates as true.
Dim dtDate as new DateTime(2010, 10, 5, 0, 0, 0, DateTimeKind.Local)
Dim lDateInBinary as Long = dtDate.toBinary()
If dtDate.toBinary() = lDateInBinary then
'Hits
Else
'Doesn't Hit
End If
Here it shows two longs that are very different as being equivalent. In my particular problem, I have a dictionary who's key is a Long and when I try to get a value by key using DateTime.ToBinary it doesn't find the a matching key since the numbers are different.
Why are these numbers different? Why do they evaluate to be the same? They are both within the bounds of the min/max of a Long, unless I'm overlooking something (it's been a long day)..
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Feb 15, 2010
I need to get the datetime.now but i dont need the format.datetime.now=15/02/2010 16:22:22i need this format (20060731 21:59:42)
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Mar 30, 2009
I have a dropdownlist that displays time only.Like 8:00AM,8:30AM............When i save this time to database i want to save as todays date + time.eg:8:00AM as 03/30/2009 8:00:00:000.
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Nov 17, 2010
is there something that can be called to indicate the lowest datetime possible?
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Aug 28, 2009
I am working on Search of records from Database between range of two dates. I implemented it with two textboxes for StartDate and EndDate and it is working fine.Now i want to attach Calender to the textboxes so that user may not have to type the dates instead user may just select the Startdate and Enddate from two Calenders.I tried with adding two DateTimePicker and used following code:[code]I have two queries:
1) DateTimePicker desplays date and time in the Textbox, I want that only Date is displayed in the Textbox.
2) How i can attach DateTimePicker directly to Texbox so that on runtime when i select a date from DateTimePicker it should immediately display in Textbox.
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Apr 11, 2011
From what I can tell Date and DateTime have the same functionality. Is there a reason why I would want to use one instead of the other?
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