VS 2008 - Checking If Date Variable Is Not Set
Feb 28, 2010
In the following code, a Date variable is declared but not set to anything:
Dim myDate As Date
What's the proper method of checking if the Date variable is "new" and not set to anything?
For example, getting the lowest date value from an array of dates:
Dim dtMostRecent As Date
For i As Intger = 0 To myDateArray.Count - 1
If myDateArray(i) < dtMostRecent Then dtMostRecent = myDateArray(i)
Next
In the code above, I need a way to check first if dtMostRecent is unassigned, in which case just give it the first value, after which it can be compared with subsequent values. How to check if a Date variable is unassigned.
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Sep 7, 2009
I need to check if a value from a date column is equal to null. I can't find how to do it.
Wat I got now is:
if ds.tblBooking(row).CancelledOn.compareTo(dbnull.value) = true then
But this doesn't seem to work, I think it's because I'm using a strongly typed database.
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Feb 21, 2011
I'm fairly new to ASP.NET & VB.I've been asked to take an existing textbox that is automatically filled with the current date and allow the user to either add a "+" or "-" and a number or a spcific number and convert that into a date.I underdstand the basic concept on how to do this, but I'm running into some problems using the proper commands in order for this to work.The Textbox is called txtDate.What I've tried to do is this:
If txtDate = '+' Or '-' Then
DateAdd("d", txtDate, today)
End If
Here is what the whole thing looks like:
Protected
Sub
DateEnter_Click(ByVal
sender As[code].....
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Nov 7, 2011
I have several records in a database that have Start and End Dates
09/15/2011 - 09/30/2011
10/15/2011 - 10/22/2011
11/01/2011 - 11/15/2011
When user stores a record, I need to make sure dates don't overlap.My simple code checks date ranges within a specific record (e.g. user enters 9/16/2011 or 10/21/2011, I throw an exception.)But, on the slim chance a user gets creative (e.g. 10/14/2011 - 10/23/2011 or even 10/14/2011 to 11/16/2011), now they have circumvented my check.BTW, the user could enter 10/14/2011 to 10/23/2011 if they were editing the record that contained values 10/15/2011 - 10/22/2011.So, I'm trying to solve this riddle with a linq query. However, what I have isn't working exactly right.
UPDATE Nevermind about code not working. While trying to provide an example to expand on Miika's repsonse, I found my answer. So, giving credit to Miika for pointing me in the right direction and posting my working code below:
Here's my code:
Private Sub CheckForOverlap(myMonth As Messages.MyMonth)
Dim am As New MyMonth()
Dim amCollection As Messages.MyMonthCollection
[code]....
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May 30, 2011
I have a Date variable called Time1In.
I'm getting a time value as a string from Excel, so I assign the date variable a value like this:
the string value coming in from excel is this:
30/12/1899 7:40:00 AM
my code gets the time value and assigns it to the date variable:
TimeIn1 = TimeValue(strTimeIn1)
the Date variables value is then this:
#7:40:00 AM#
which inserted into my database datetime field then looks like this:
0001-01-01 7:40:00
That causes errors when loading the page. I need to set a date value on the date variable. How can I properly append a date to the variable?
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Jul 30, 2009
Is this the correct way to get a datetime value using a sql datareader:
existingETA = existproformaReader.GetDateTime(0)
I want to assign the value to a date variable and compare it to another date variable.
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Jun 24, 2009
I need to check my field in format ddMMyyyy(ex 12/03/1990) whether in interval of two dates that user picks from two date picker controls. Two date pickers are in custom format dd/MM. It does not matter for me if its between particular years. I need just to know if given Birthday belongs to interval taken from screen. Each datepicker gives values dd/mm/yyyy. I do not know how to check it. For example:Given date 12/03/1990 . User select two values from screen: From 01/01/1950 Upto 30/04/1949(or 1990, or 2000)
Result should be True.Because 12 march is between 01 Januar and 30 April.
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Jan 11, 2010
I'm working on a small accounting app. I have a query to show transactions with a running balance.
SELECT transactionid, transactiondatetime,
amount,
(SELECT SUM(amount)
FROM dbo.transactions as D1
WHERE D1.transactiondatetime <= D0.transactiondatetime) AS balance
FROM dbo.transactions AS D0
I capture a gamesheet for a certain week. so if I select a date on a monthcalendar the sheet applies to the weeknumber of the selected date. When I save transactions I take the date at the last day of that week as the transactiondate. I need to store a datetime though because my query works of the datetime to get an accurate running balance. How can I append now() time part to my date variable and then store that in a datetime variable to get a transactiondatetime.
Here is my code for getting a transactiondate:
Dim dt As New Date
dt = Me.MonthCalendar1.SelectionStart
'get last date of week. Friday
Dim tdate As Date = dt.AddDays(5 - CInt(dt.DayOfWeek))
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Jan 3, 2012
I am trying to parse a date from a textbox and store it in a date variable
Dim enddt_2 As Date = Date.ParseExact(txtenddt.Text, "dd/MM/yyyy", System.Globalization.DateTimeFormatInfo.InvariantInfo) 'txtenddt.Text
expenddt_1 = enddt_2.AddDays(-1)
enddt = enddt_2.ToString("dd/MM/yyyy")
enddt is a Date variable and when i convert enddt_2 to a string i get the error as
Conversion from string "17/01/2012" to type 'Date' is not valid.
Let me clarify, if a value in textbox is 17/01/2012 than after parsing the value is changed to 01/17/2012 (my systems Region and Language are dd/MM/yyyy) in enddt_2 and when i try to convert to dd/MM/yyyy format and store into a date variable i get the above error. This error comes only for the dates after 12. i.e a date variable accepts a date in MM/dd/yyyy format.The dates before 12 work fine, i.e for all dates from 1 to 12 there is no error.How can i make enddt store the date in dd/MM/yyyy format.
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Oct 25, 2011
I have an ASP.NET application that crashes when a null date value is returned.
The code line is:
excelWorksheet.Cells("A" & xlRowCounter).Value = IIf(IsDBNull(dRow("sysdate")), "", Format(dRow("sysdate"), "MM/dd/yyyy"))
Error message:
ERROR: System.ArgumentException: Argument 'Expression' is not a valid value.
How would I check for a null date, and replace it with "" in my app ?
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Apr 4, 2009
I need to pass javascript date value to vb.net function. [code]retrieve string from hidden field in server code and parse it using date.parse [code]doesnt match vb date format. I am getting error that its unparseable.
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Feb 20, 2009
I have declared a class in VB.NET using VS2K5 with some shared variables and made that class a dllI made use of that dll in another project and tried to make use of those variables. Even though I can able to make use of them, Im unable to view the values of those variables like the values of normal variables when Im debugging. Is there any way that I can watch the values of those shared variables during debugging.
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May 21, 2011
For my uni project I am designing a system that allows you to book a job into an Access database. My question is, Can you use a something like a calender or a diary to check if there is a job already booked on a certain date (like a duplicate date?), and in turn if there is, show an error message to inform the user that a job can't be booked on that date?
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Dec 1, 2011
I want to prevent a form from loading if the systems regional datetime settings format for the date is not in the form of dd/MM/yyyy.
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Apr 13, 2011
I am being forced to us Option Strict in my class and this is a new feature to me. Right now my code is having trouble comparing the current time to be added (A Date) with the list of times (Object). Here is my complete code
Option Strict On
Public Class schedulebookForm
' handles Add button user event
Private Sub addButton_Click(ByVal sender As System.Object, _
[Code]....
Problem is inside TimeTaken Function, inside the For.. Until. Basically the If... Then Statement. I tried. .contains, Select Case, and a few other alternatives.
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Aug 10, 2011
Not so long ago, I saw somewhere a solution how to check if string is date in yyyyMMdd format (i.e. if it can be converted to date if written in such format). I can't find it anymore but I think is had something to do with DateTime.TryParse method but I can't get it to work. I can get it to work if string is in dd/MM/yyyy format, but dont' know how to make it with yyyyMMdd format. If I'm not mistaken neither of DateTime.TryParse method parameters is for assigning date format...
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Feb 24, 2011
I have the following Java code that i am trying to dissect to better understand what all it is doing:
try {
String userName = System.getenv("USERNAME");
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH.mm.ss");
OracleDataSource ds = new OracleDataSource();
ds.setDriverType("thin");
ds.setServerName("xxxxxxx");
[Code]...
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Feb 27, 2012
I'm implementing a State Machine in WF 4.0. In some transitions, I have added a condition where I check that some variables have the expected values. The variables are enums and booleans, and everything is fine.
However, now I tried to evaluate when a property is null. I have and argument in my workflow, let's say, 'MyArgument'. In a transition, I try to put a condition like 'MyArgument.MyProperty = Nothing'. I never developed in VB.NET, I don't know if I'm missing something here...
VS2010 gives the following error: "Error 4 Compiler error(s) encountered processing expression "MyArg.MyProp = Nothing".
Operator '=' is not defined for types 'XXXX' and 'XXXX'
The type names are exactly the same, and I have debugged VS2010 to ensure that my assembly is not loaded from 2 different locations.
How can I check if the property is null or not?
BTW, I'm using VS2010 SP 1, with .NET Platform Update 1 installed, on W7 64 bits.
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Jan 16, 2012
I'm trying to check if a variable has been defined as a nullable Guid. eg.
Dim myGuid As Nullable(Of Guid) or Dim myGuid As Guid?
It seems doing a myGuid.GetType returns the underlying type, that is type Guid, not Guid?. So testing myGuid.GetType Is GetType(Guid?) always returns False.How do I find out if myGuid is a nullable type?
Ed: I can do the following, which correctly returns True for "Guid?" and False for "Guid":
Not Nullable.GetUnderlyingType(GetType(Guid?)) Is Nothing
The problem is that I don't know how to retrieve the nullable type from the variable itself, in order to test it. I've only been able to get the underlying (non-nullable) system type.
I've written a db helper function. I pass it an object comprised of public members, representing the row data of a table. The members are the table columns.Using reflection, I loop through these public members to create an INSERT statement for a command object and populate its parameters with the values in those members. So far so good.But now there's a table which has a uniqueidentifier column which I must not populate from the row object, as it defaults to "NEWID()" (using SQL Server 2008). Instead of skipping all Guid columns, which would be easy, I only want to skip ones defined in the row data class as "Guid" (non-nullable).Basically, I'm using the Guid? (Nullable) type to indicate it's ok to populate that uniqueidentifier column with data. If it's non-nullable, that tells me to skip it because the column has a NEWID() default value.
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Oct 31, 2011
I've never really used the Check List Box in the past, however, for the recent program I am developing, I am using this control rather than individual check boxes scattered across the form.Anyway, I want to be able to program through code which items get checked in this checked list box. Specifically, I have a variable that contains the text of each check box that I want checked.With a normal check box, I can simply say:
Dim strNames As String
strNames = "John Doe, Mark Johnson, Mike Brown, Cindy Smith"
If strNames.ToString.Contains("Mike Brown") Then[code]....
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Aug 31, 2009
I have below code in vb.net.
[Code]...
I want to check at client end whether the entered date in text box is future date. I mean this textbox should allow future date only. code the above problem using jquery or vb.net
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Mar 25, 2010
I am getting the error:"Range variable 'sender' hides a variable in an enclosing block or a range variable previously defined in the query expression."for this
Imports System.Data.SqlClient
Imports System.Linq
Public Class Form1
[code]....
I can select any other item from the table without the error. "sender" has the same properties as "receiver" in the SQL table.
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Feb 7, 2011
i'm trying to use "date" as the name of my variable as i need to use it a parameter to some tweets API. so am wondering is there a way to declare date as a variable because in visual studio vb.net date is a class on its own and we cannot use it as a variable name.
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Jan 12, 2011
In the Session_Start of the Global.asax i have
Sub Session_Start(ByVal sender As Object, ByVal e As EventArgs)
Session("login") = False
[code]....
Why i am getting error the error Object reference not set to an instance of an object. at line
If Current.Session("login") Is Nothing Then
while checking for the login state as follows?
If GetLogin = False Then
'Do something
End if
I mean i have already created the instance on the Session_Start... Haven't i?
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Apr 1, 2009
How do you declare a variable as a Date and initialize it with a date before year 1. I would like to caluate historical BC dates using a fuction that returns the ellaspt time.
I've used this line of code however I can't to work setting the date value to a negative.
Dim
myDate As Date = CDate("2/6/1400")
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Jul 16, 2009
I have a date, myDate = 07/16/09 14:22I would like to arbitrarily force the time portion of it to a predetermined value like myDate = 07/16/09 18:00.
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Jan 1, 2012
I got Minimum date from database using sql qry, And when i try to store that min.date in one variable, its getting error, PlZ help me. for below coding.
Dim qry as string
Dim Min_Date As Date
If SqlCon.State = ConnectionState.Closed Then
SqlCon.Open()
[code]....
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Sep 22, 2011
In my ASP.Net (VB Code) that I had 3 variable to store 3 different date.how can I compare 3 variable to find the last day between 3 date? [code]
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Mar 7, 2011
I am trying to pull the modified date of one file in a folder through a SSIS script. I tried doing this through the system.IO namespace as it contains the GetFileName method. This isn't working & I was wondering if there was a name space that contained the modified date method for a file if I specified the path to the filename. I am looking to return the modified date variable in whichever way this may be possible.
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Feb 1, 2012
I have two datetime variables in VB.Net [code]I want to add both these variable in single DateTime variable , i didn't find any .Net function to do that.Is there any other way to do it?
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