Nullable DateTime And Ternary Operator?
Nov 15, 2010I'm having problems with a Nullable DateTime in VB.NET (VS 2010).
Method 1
If String.IsNullOrEmpty(LastCalibrationDateTextBox.Text) Then
gauge.LastCalibrationDate = Nothing
[code].....
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Assign A Value To A Nullable Integer Via A Ternary Operator?
Aug 24, 2011dim val1 As Integer? = If(5 > 2, Nothing, 43)' val1 = 0 dim val1 As Integer? = If(5 > 2, Nothing, Nothing)' val1 = Nothing What gives? Is this a bug, or am I overlooking something?
View 1 RepliesWhy Does The Ternary Operator Accept A Nullable Boolean
Oct 6, 2011The following compiles in VB.NET (with Option Strict On) and outputs False:[code]Why does that work?The documentation clearly states that the three-argument version of If requires a Boolean as the first parameter:[code]So, why does this work? Is it a bug (or "hidden feature") in the compiler or is it a bug in the documentation and Boolean? is actually a valid type for the first argument of If(a, b, c)?In C#, b ? x : y does not compile if b is of type bool?.I've reported this issue to Microsoft Connect. Someone from MS has replied and confirmed that the documentation will be updated to include the Boolean? case.
View 4 RepliesAssign A Value To Nullable Integer Via A Ternary Operator / It Can't Become Null
Apr 19, 2012If you assign a value to a nullable integer via a ternary operator, it can't become null..While this question may seem like a duplicate of many, it is actually being asked for a specific reason.Take this code, for example: Dim n As Integer? = If(True, Nothing, 1) In that code, the ternary expression should be returning Nothing, but it's setting n to 0. If this were C#, I could say default(int?) and it would work perfectly. Now it looks like I am going to have to ditch the ternary and use a regular If block, but I really want to use the ternary. If Nothing were truly VB.NET's equivalent to C#'s default, how can you explain this behavior?
View 1 RepliesIs There A Conditional Ternary Operator
Feb 23, 2009In Perl (and other languages) a conditional ternary operator can be expressed like this:my $foo = $bar = $buz ? $cat : $dog;Is there a similar operator in VB.NET?
View 2 RepliesSimilar To The Ternary Operator In .net?
Mar 29, 2011I saw this in some vb.net source code:Dim sTest As String = "" & drTest("column")
I was told that if drTest("column") is nothing, then sTest will be assigned "", so it is in effect doing:
Dim sTest As String = If("",Nothing,drTest("column"))What is the downside of doing it the first way I showed?
What is the difference between using If and IIf?
Ternary Operator In Gridview
Aug 20, 2011I am looking to make this statement work in a VB.net page:
[Code]...
The ternary operator is causing a error: Compiler Error Message: BC36637: The '?' character cannot be used here. I want to use a tenary operator to display text based on the the field Inactive containing a true or false text value.
Translate A Ternary Operator Into VB?
Feb 24, 2010I'm usually reasonably good at translating C# into VB, but I'm a bit stuck partially due to the ternary operator in this function and also because I don't fully understand what is happening with the "from x in dataSource.OfType<object>() select 1).Sum()"
[code]...
Lambda Expression With Ternary Operator In VB?
Feb 26, 2010Lambda expression with ternary operator in VB?
View 15 RepliesTernary Operator VB Vs C# Resolves To Integer
Nov 10, 2010Suppose we have a nullable value in vb.net: Dim i as Integer? We want to assign a value to it, basing on a condition, and using a ternary operator, because it's so neat and stuff: i = If(condition(), Nothing, 42) That is, if a condition is true, employ the null-ability, otherwise the value. At which point the shooting occurs. For no apparent reason VB compiler decides that the common base type for Nothing and Integer is Integer, at which point it silently translates the statement to: [Code]
View 5 RepliesTernary Operator IIf Throwing Strange Exception
Mar 30, 2011I am having a weird problem. IIf is messing up when I am working with an array. Apparently it is checking my else statement even though it isn't activated. Here is some code that demonstrates the issue:[code]
View 2 RepliesSetting Nullable Type With IF Operator Failing?
May 27, 2009Why does this give variable A the value of zero (instead of setting it to nothing)?Dim A as double? A=If(2<3, Nothing, 6)
View 11 RepliesAssigning Result Of If Operator To System.Nullable Type
Aug 30, 2011When using the If operator [URL] to assign a value to a System.Nullable object, if the result is Nothing (null), then 0 is assigned to the object. Example: 'Expected value is null (Nothing). Actual value assigned is 0. Dim x As System.Nullable(Of Integer) = If(1 = 0, 1, Nothing) If x is a nullable type, why is it being assigned the default integer type of 0. Shouldn't it receive a value of null?
View 2 RepliesC# - Comparing The Nullable DateTime's?
Nov 17, 2010I am a c#/asp.net developer and I am having to work on a VB/asp.net. I have two variables
Dim originalDate as DateTime?
Dim newDate as DateTime?
Both nullable datetimes, originalDate is a nullable date I am getting from the database and newDate time is set in code, I need to compare them, they can either both have dates, neither have dates or one have and one not.
I have a bit of code as follows:
if origEndDate = origEndDate then
When both origEndDate and origEndDate are "nothing" this statement is false (well when I run it in the watch window it comes back as nothing)!I don't understand why this is the case because I was under the impression doing an "=" compares the two values and as they are the same surely it should be true? What syntax should I be using as in C# I can do the above as so:
if (origEndDate == origEndDate) { }
and it will come back as true.
VS 2010 Nullable DateTime?
Jun 3, 2010For a project I need to convert a date field in my SQL Server 2008 Database into a VB.net ListOf. Most of the records in StartDate field are NULL. VB.net doesn't recognize null values for DateTime.I need the NULL values to be dismissed, as they will be returned in a ListOf for a web service that I'm creating.
Here is my syntax and a sample of the current returned values in the XML message of the ListOf:
Class Property StartDate() As System.Nullable(Of DateTime) = Nothing
asmx.vb myUserRoleAppInfo.StartDate = myPermissionUser.StartDate
XML Message (Listof)
[Code]...
C# - DateTime Nullable Exception As A Parameter?
May 8, 2009I have a Search Form that can search by a few different fields. The problem field is birthDate. On the form it is a string. In the SQL 2005 db it is a DateTime that can be null.
The code below is sequential as far as declaring the variable on the form and then setting it. Then the call to the BLL and then the call to the DAL.
On this line -->
dgvSearchResults.DataSource =ConnectBLL.BLL.Person.Search(_firstName,_middleName,_lastName,_sSN, (DateTime)_birthDate,_applicationID,_applicationPersonID,_fuzzy);
[Code]....
Linq Grouping By Nullable Datetime And Using This As Criteria?
Nov 17, 2009I am struggling with a nullable datetime column [DateInsp] in an ASP.NET app which uses SubSonic3, Linq, MS SQL Server 2005.I had this all working when the datetime column [DateInsp] did not allow nulls. A new requirement forced me to set the [DateInsp] column to allow nulls and now I am struggling getting this piece of functionality to work properly again.
Problem 1:I need to first render a dropdown list of the 7 most recent inspection dates for a given inspector (this is a grouped list of the 7 most recent dates for the inspector). Here is the TSQL that I need to convert to Linq syntax:
declare @InspectorID varchar(5)
set @InspectorID = 'GPA'
select top 7 convert(nvarchar(30), [DateInsp], 101) InspectedDate
[code]....
If I can't get this work properly using Linq, BUT I can/could build a stored proc to return the list of dates and throw that into a dropdown. Fair enough. I've been fighting with the Linq syntax?
Problem 2: I need to use the selected date in the dropdown mentioned above to pull the correct records for this inspector and the correct date. Again, this is a nullable datetime field and this is real sticking point for me.
Here was the original Linq syntax that accomplished the requirement before I had to change the datetime field to allow Nulls:
Dim query = (From i In db.IncomingInspections _
Where i.InspectorID = User.Identity.Name _
Group By Key = New With {i.DateInsp} Into Group _
[code]....
For some reason I can't use the .Value property; I get: The member 'Value' is not supported I get: "Incorrect syntax near '<'." if I try to add the date comparison to the where clause too.
C# - Set System.nullable Of Datetime As An Optional Parameter In A Subroutine?
Nov 13, 2011I tried the following, but i get the error
constant expression is required
Public Sub ExampleSub(ByVal Test as string,
Optional ByVal fromDate As System.Nullable(Of DateTime) = Date.Today)
'A Great sub!
[Code].....
DateTimePicker Bound To Nullable DateTime Field But No Null?
Apr 7, 2010I have a date time picker bould to a Nullable Datetime field in a sql server datatable. The ShowCheckBox option is set to true. If the user unchecks the checkbox on the datetimepicker I would like to the field to be set back to null in the DataTable. The default behaveour does not seem to do this and there is no specific event for the uncheck.
Private Sub dtpCertDate_ValueChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles dtpCertDate.ValueChanged
If dtpCertDate.Focused Then
[code].....
Re-write Conditional Logic That Involves Checking Three Nullable(Of T) Values In An Equality Operator Overload?
Jan 28, 2011So I'm writing the equality operator overload (Operator =())for a custom object, and the resulting mess of If conditionals is just an eyesore. But so far, it seems like the only sane way to check the values to as to match the specific behavior of this object.
The rules are:Num1 is required, period, and both the left and right operands and must be equal for True. Else, False.Num2 is optional, but if specified, must be present for both the left and right operands, and must be equal for True. Else, False.Num3 is optional, but can only be specified if Num2 is also present. Else, False.Num3, if specified, must be present for both the left and right operands, and must be equal for True. Else, False.
[Code]..
I also know that I could cache elements of the checks into booleans and then use those to reduce the amount of text. But that seems like a waste of cycles just for code readability. So I wanted to know if the SO community had better thoughts on reorganizing it, just in case I'm being too verbose with my checks.
Error - Soap Serializer Does Not Support Serializing Generic Types : System.Nullable`1[System.DateTime]
Oct 2, 2009Im working on my first n-tier application. I am trying to serialize a structure and Im getting an error"Soap Serializer does not support serializing Generic Types : System.Nullable`1[System.DateTime]."Here is the structure that is being serialized
Namespace Structures
<Serializable()> _
Public Structure structAllergy
Public AllergyID As String
Public ProfileID As String
[code]....
The bold line is the line that is throwing the error.
Error: Option Strict On Disallows Operands Of Type Object For Operator '='. Use The 'Is' Operator To Test For Object Identity
Jan 27, 2010I am tightening up my coding with the Option Strict set to ON. It has now produced alot of errors. An example of this is:
If AllocatedDGV.Rows(i).Cells("RoomNumber").Value = RoomsAvailableDGV.Rows(j).Cells("RoomName").Value Then
It gives me the following error: Option Strict On disallows operands of type Object for operator '='. Use the 'Is' operator to test for object identity.
Option Strict On Disallows Operands Of Type Object For Operator Use The 'Is' Operator To Test For Object Identity
Apr 6, 2012I need to write an interface to get data to/from our data files.
We have a low level class that holds field values for each record read from the files.
This just holds two values, the value read from the file (DBValue) and the updated value that may need to be written back to the file (CurrentValue).
These values may be any of the standard value types (integer, date etc) or a string.
Either value (DBValue or CurrentValue) may be null if not defined.
I have written the class to manage this data which works fine while option strict is NOT on.
But we have an office policy of having option strict on all the time.
When I put option strict on, my object value comparisons fail with the error: "Option Strict On disallows operands of type Object for operator '='. Use the 'Is' operator to test for object identity."
Question, how should I change the following code to handle option strict on ...
This is all running on Visual Studio 2010
[Code]...
Coalesce Operator And Conditional Operator In .NET?
Mar 10, 2009Possible Duplicate: Is there a conditional ternary operator in VB.NET?
Can we use Coalesce operator(??) and conditional ternary operator(:) in VB.NET as in C#?
Convert String To Datetime & Calculate The Datetime?
Mar 23, 2011how to convert string to datetime and calculate date
View 3 RepliesMatch A Certain DateTime Value With Current System DateTime
May 7, 2010I'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.
View 1 RepliesMatch A Certain DateTime Value With The Current System DateTime?
May 1, 2010I'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.
Update Datetime Field With Empty Datetime?
Aug 8, 2011datetime1 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
View 1 RepliesPass A Nullable Valuetype Into A Non Nullable Valuetype?
Sep 17, 2009I accidently wrote some code today that was like this[code]...
I immediately noticed the issue, but I had already hit the run button. It compiled successfully, I ran it through to the section and it threw an exception.
You can't do this in C#, it gives a compile error "cannot convert from 'int?' to 'int'".
Is there an 'Option Explicit' type switch that I can turn on to ensure that this sort of error does not occur again?
How To Use Operator As A Comparison Operator
Nov 11, 2009I want to perform equality comparison in VB.NET and cannot get it to work. Error: value of type Boolean can not be converted to System.Drawing.PointF
[code]...