How do I set a null value for an optional DateTime parameter in a constructor?
I'm using the following constructor below and I want the optional parameter admissionDate to be a null DateTime. Setting it to Nothing actually gives it a value (something like #12:00:00 #).
Public Sub New(ByVal obj1 as Object, Optional ByVal admissionDate As DateTime = System.Data.SqlTypes.SqlDateTime.Null)
How to test the null value BEFORE calling the other constructor?
' class MyHoyr '
Public Sub New(ByVal myHour As MyHour)
' Can't doing it here !!!! '
[code]....
I received this error when im trying to save the date in my database.
SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM. Description: An unhandled exception occurred during the execution of the current web request.[code]...
I have a databound ComboBox on my form. Is there any way that I can make the first field blank.
I can do this with a DropDownList in the HTML part of .Net but is there a way to do it for a ComboBox?
is there any trick (because I can't think of anything else ! ) to massively set all of the properties , of a user defined class , to their null values ? You see , I have a class called Apartment and it has a lot of properties (it only has properties , no methods or events , if that's important) and those properties are either strings , doubles or integers . I want each time I create a new instance of that class (a new apartment , that is) to automatically set those properties to their null values . That is all of the strings to be equal to "" and all of the numbers to be equal to 0 . Back in VB6 I could rely on VB6 to do this automatically , but now in VB .NET , whenever I create a new instance of a class , all the properties start with the value = Nothing . I know I can define every property in the class module like that : Public MyVariable As String = "" but I'd like to keep them as they are and set their null values directly whenever a new object of that class is created .
View 8 RepliesIm writing an app which connects to a SQL Server database, via datasources / datatable.When Im looking at my .xsd I can see DataTables containing DataColumns. Each DataColumn has a 'NullValue' property which defaults to '(Throw exception)'.Because I have nulls in my tables I have gone through the fields and set all System.String fields to NullValue = 'Empty', System.int32 field to NullValue = 0.
View 1 RepliesI have an abstract class which requires a delegate to function. I pass the delegate into the constructor. Now that I have a non default constructor I need to call the abstract class's constructors from the concrete class which means that I need to use MyBase.New(...). I have included a quick example below.
Public MustInherit Class BaseClass
Public Delegate Sub WorkMethod()
Private _Work As WorkMethod
[code]....
I have tried to do this but I keep getting the following error: "Implicit reference to object under construction is not valid when calling another constructor".Can I not do what I am trying to do above? I initially had the delegate setup in its own setter method. But then I am creating a deceptive API because it does require a point to a method to work properly.
what's the rationale behind this limitation: Constructor call is valid only as the first statement in an instance constructor i want to pass an argument to my constructor which validates this argument and calls mybase.new according to this argument but it doesn't let me
example:
Public Class prob
Inherits System.ApplicationException
Public Sub New(ByVal problem As String, ByRef inner_exception As Exception)
[code]....
I have a databound DataGridView, and I'd like to keep one column in front, with a slightly smaller width than the default. The grid's AutoSizeColumnsMode property is set to Fill so that the columns fill out the entire grid. This makes the first column equally large as all others, which is why I need to set its width manually. The smaller column is the first one with the checkboxes. I have two grids that I need to do this with, and for some reason it works just fine with the first grid, but gives a null reference error on the second grid...
Here's the code for the first grid (working fine):
vb.net
Public Sub UpdateTodoGrid()
' Load todo items
todoGrid.DataSource = _TodoManager.LoadAll()
' Set backcolor
For Each row As DataGridViewRow In todoGrid.Rows
[Code] .....
As you can see, the code is exactly the same (except for not setting the BackColor of each row and not using the ReadOnly property*). When I run this code, it gives me a null reference error ("Object reference not set to an instance of an object.") on the line where I set the column's Width. Obviously 'col' is not Nothing (otherwise it would have errored before that line), and there's nothing else there that could be Nothing... I assume that something happens internally in the grid when you set the width of a column, and that there is a null reference there, but obviously I have no control over that.
The grid's are absolutely the same, as the second grid is just a 'copy' (meaning I copy/pasted it in the designer) of the first. So all their properties are equal. I thought maybe the ReadOnly properties were the problem, but I tried putting them in in the same way and the issue did not go away... The first grid is not ReadOnly (because the checkboxes need to be editable), but all rows except the first are, while the second grid is completely ReadOnly.
Why below code has error in VB.net 2008?Dim Object1 As New Class1Object1.SetId = If(rbSet.Checked = True, Convert.ToInt32(txtSetId.Text.Trim()), DBNull.Value)What I'm trying is to set a property of an object by a condition.
View 1 RepliesI have a fairly simple piece of code:
Private _PurchaseDelivery as PurchaseDelivery
Protected Overrides Sub InsertItem(ByVal index As Integer, ByVal item As PurchaseDeliveryItem)
[Code]....
Which is inside a class which overrides a custom list base. The code is occassionaly throwing an unhandled exception, System.NullReferenceException, on this line when used in production:
If _PurchaseDelivery IsNot Nothing AndAlso _PurchaseDelivery.DefaultSKUBinID.HasValue Then
DeafultSKUBinID is declared as an Integer? (Nullable Int) in the PurchaseDelivery class. I cannot see what might be causing this error, why would this be returning an error?
How to check whether a column is null i use the following code but I got this error "Input string was not in a correct format."
[Code]....
When I put a break point to the last if clause in the sub ("If (backOrder < 0) Then", see below) it runs until the break point, if I put the break point further below, I get the following error:
Cannot insert the value NULL into column 'OrderID', table 'WHM.dbo.OrderDetails'; column does not allow nulls. INSERT fails. The statement has been terminated.
I've discovered first hand that it only happens when prodqty is bigger then qtyOnStock, thus executing the if clause.
The code:
Private Sub NCOSubmit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles NCOSubmit.Click
Dim sqlText As String = ""
[Code]....
I need help and wondering if you can help me to get my first project...it's a hobby and wondering if you can get me code for this so i can see how it does it* Evaluate( ) Prints the evaluation of the hand to the evaluation Label.
o If IsFlush( ), prints "flush; "
o calls SetPipArray( )
o Uses a For Loop to go through pipArray. For each element, uses a Select Case statement to
[code]....
In our projects we use setting variables to store user setting for the applications. Moreover, with every latest version of the applications, we upgrade these variables to retain user settings.Normally, this works fine, but recently one of my end user reported an error i.e.Configuration System failed to initialize". The error is related to user.config file. Therefore we requested the user to send us his file.After received the folder, we noticed that it contains 3 files (3begfjb.newcfg,3begfjb.tmp and user. config). 3begfjb.tmp is an empty file, while 3begfjb.newcfg and user.config are identical files. We tried to open these files but the data in user.config isn't proper xml rather its unreadable formatted file.Do any you guys had experienced this sort of issue or any ideas how and what may have created these files and corrupted user.config file.
View 3 RepliesI am trying to create a treeview in VB.net, the data has to be loaded from MSAccess 2010 database. When I try to run this program I get error : Argument Null Exception was unhandled, 'column' argument cannot be null and the program crashes. I have pasted the code as under:
Imports System.Data.OleDb
Public Class frmRating
Private Sub frmRating_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles
[code].....
When is it run? Does it run for each object to which I apply it, or just once? Can it do anything, or its actions are restricted?
View 3 RepliesA project has a class (CAR Class) with the folloiwng details and the CARADMIN cLASS with the following details: The cardAdmin class has 2 constructor Public Sub New() & Public Sub New(ByVal rec As Rectangle) I dont know how to code the latter constructor..
cAR Class has this method/properties:
Public Class Car
Inherits HVSprite
Private fSoundFile As String
[code].....
I have a defualt constructor that has a object of a Database connectivity class:[code]therefore in theory i have to call the defualt constructor of Question from overloaded constructor. [code]How every in realitty is it possible to call the defautl constructor from the overloaded constructor
View 5 RepliesDo not know how to convert Me.Base to C#Imports Microsoft.VisualBasic
Public Class ReplaceHTML
Inherits System.IO.Stream
Private Base As System.IO.Stream
[code].....
how to pass value other than from constructor.
In my code....value are usually passed through constructor.
ie everything is declared in constructor and while executing, these values are defined in new object.
I am rewriting a C# class in VB. The C# class has a static constructor in it:
static Class()
{
...
}
which, through the Call Stack, I found is called by the main window's InitializeComponent() method.Everywhere I've looked has told me that the corresponding static constructor in VB is just:Shared Sub New()
but this method is never invoked. Am I creating my VB static constructor right? Is it likely something else that has nothing to do with my static constructor?
A former co-worker wrote a class in C# that was to be used as an attribute. I'm having to convert his work to VB (yeah, it's pointless and way more work than necessary, but management thinks it's a good idea). Unfortunately I'm having an issue because one of the main properties of the class is an ArrayList which is set with a ParamArray in the constructor. The class looks like this (note I've tried to abstract out the problem, so this is a simplified version of the class only)
<AttributeUsage(AttributeTargets.Field Or AttributeTargets.[Property])> _
Public Class LabelAttribute
Inherits Attribute
Public Sub New()
[CODE]........
In the first one, there is just the single label being added. No Problem. In the second one there are 2 different labels being added. Again, no problem. The third one, however, is a problem because it's assuming that the "Description", which is supposed to be the description is instead being interpreted as another label.
This wasn't a problem in C# because it could be set as follows:
[CODE].................
Of course this doesn't work in VB because optional parameters aren't referred to by name as they are in C#. As a stopgap I've changed the constructor to allow only a single label like this
CODE]..................
But that undermines some of what this class is meant to do. Does anyone know how, or even if I can get the same basic functionality to work in VB?
Think there must be a way to make the existing design work. Imagine this class was built into a library that I could not modify. Would I be forever forbidden from setting Description because of this design?
Why VB.NET (vs C#) does not "inherit" the constructors with parameters?
Public Class StopLine
Inherits Microsoft.VisualBasic.PowerPacks.LineShape
Public Sub New()
MyBase.New()
[code]....
I've been searching for a while now and can't find a way to add a constructor to the Rectangle Structure.
Is this even possible without inheriting from the class?
Im having trouble with assigning a Rectangle to this constructor
fTrainAdmin = New TrainAdmin( )
I need to put following code in the Constructor of my startup form.
JohnKenedy.BusinessSQLEXPRInstaller _ins = new JohnKenedy.BusinessSQLEXPRInstaller(" _ <Installation Display Name>", "localhost", "<New database instance name>", _
"<new database name>", "<database password>", "<database backup filename>");
if (_ins.IsDone == false) _ins.ShowDialog();
if (_ins.IsRestart == true) {
Application.Exit();
this.Close();
return;
}
But I really do not know what the Constructor is and how to access it?
I know that you cannot specify a constructor in an interface in .Net, but why can we not?
It would be really useful for my current project to be able to specify that an 'engine' must be passed in with the constructor, but as I cant, I have to suffice with an XML comment on the class.
I'm not sure if this is possible or not. I have a number of different classes that implement interface IBar, and have constructors that take a couple of values. Rather than create a bunch of almost identical method, is it possible to have a generic method that will create the appropriate constructor?
private function GetFoo(Of T)(byval p1, byval p2) as List(Of IBar)
dim list as new List(Of IBar)
dim foo as T
' a loop here for different values of x
foo = new T(x,p1)
list.Add(foo)
' end of loop
return list
end function
I get:
'New' cannot be used on a type parameter that does not have a 'New' constraint.
I searched quickly and not find an explicit answer at the following question:Why VB.NET (vs C#) does not "inherit" the constructors with parameters?
Public Class StopLine
Inherits Microsoft.VisualBasic.PowerPacks.LineShape
Public Sub New()
[code].....