In C# we can do something like this:
Honda a = new Car(); and that works but the same one doesn't work in Visual Basic.NET (I am fairly new to Visual Basic)
Dim a as Honda = new Car and it says Unable to cast object of type 'SampleApp.Car' to type 'SampleApp.Honda'.
Here is my sample code:
Module Module1
Sub Main()
Dim a As B = New A
[Code]....
I have this visual basic error and i was wondering if anyone could help.Private Sub SearchToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SearchToolStripMenuItem.Click
[Code]...
I'm receiving the following error in VB.Net."Object reference not set to an instance of an object"
Imports System.IO
Public Class LoginForm
Dim Username() As String
[code].....
Is there a way for an object to call the object that contains it, like how a FrameworkElement has a Parent Property?Bill Gates look out!
View 4 RepliesI have
Public stack() As CTest
I want
Public stack() As Object
The latter is giving the error "Unable to cast object of type 'Object' to 'CTest'." when used:
Dim thestack As CTest() = testdatabase.getStack
Where testdatabase.getStack simply returns stack();
Public Function getStack() As Object()
Return stack
End Function
This fixes it, but it's not ideal (for me personally):
Dim thestack As Object() = testdatabase.getStack
So if I could keep the variable as-is (Public stack() As Object) and then do something along the lines of class.stack() = CTest I should be able to do Dim thestack As CTest() = testdatabase.getStack because the object array will programmatically have changed from Object to CTest.
I've used VB.net for several years now, but keep coming across little quirks that I don't know how to work around. Curiosity finally got the best of me, so I ask now: is there a way to create an object without assigning it?For example, say I have an Engine class, that I want to instantiate and have it immediately do whatever it needs to do. If there's nothing I need to do with Engine after creating it, I have, till now, done something like:dim myEngine as new Engine()Is there a way to avoid the "dim myEngine as" part? You certainly can in Java. I could just create an object with "new Engine()" in java and not assign it to anything.
Why do I need this? Because often I want to create a delegate object (hence I called it "engine") that performs some functionality, but otherwise I don't need to ever reference it. I used to have such objects have a "public sub perform", but have found that cumbersome -- I'd rather just create the object and not worry about remembering to call its perform method. And I find it aesthetically displeasing to create references to objects that I don't intend to use
I am working on a application that has quite a few functions involved and have been thinking of the following: If I have a function that has a few paramaters, is it more efficient to pass the objects to the function(Example 1) or reference the objects in the parent(Example 2)? Does it matter if the objects are large or not?
Example:
Class mainform
Public myGenericList As New List(Of String)
Public myDatarowArray() As DataRow
[Code].....
I have several sets of similar objects (labels, progress bars) on a form in Visual Basic 2010 on Windows. In my code, I have collections that contain data, which needs to be pushed into the value/text property of each.
I would like to get a solution similar to PHP in that I can assign values somewhat like:
For ID as Integer from 0 to count(collectionExample)
lblExample{ID}.Text=collectionExample(variableID)
...and as such to loop through so each of the different lblExample's were updated to their corresponding value.
The issue I have come to is that I cannot seem to reference an object on the form using a variable. I have also tried using something like
CallByName("lblExample" + variableID, "Text", CallType.Set, exampleCollection(variableID))... however I still can't combine the string and variable to reference the object.
Any solutions on referring to objects in VB2010 by combining a string prefix and a variable string identifier, similar to PHP's $variable{$variable} approach?
Edit: Windows Platform
VB 2008 .NET 3.5 Suppose we have two classes, Order and OrderItem, that represent some type of online ordering system. OrderItem represents a single line item in an Order. One Order can contain multiple OrderItems, in the form of a List(of OrderItem).
Public Class Order
Public Property MyOrderItems() as List(of OrderItem)
End Property
End Class
It makes sense that an OrderItem should not exist without an Order. In other words, an OrderItem class should not be able to be instantiated on its own, it should be dependent on an Order class to contain it and instantiate it. However, the OrderItem should be public in scope so that it's properties are accessible to other objects. So, the requirements for OrderItem are:
[Code]...
This error makes no sense to me[code]...
Unable to cast object of type 'DynamicTreeNode' to type 'DynamicTreeNode'.
I have an inherited TreeView with an inherited class called DynamicTreeNode inside it. I am trying to loop through the DynamicTreeNodes in the TreeView.Nodes property which is causing this error.
I am working in VB.net and have a Class, Foo, that implements an interface, IBar.I have a List of Foo's, but I need to pass a list of IBar's into a function, but I keep getting casting errors, even when I use DirectCast.My code is [code]MainWorks works, but it would be really annoying and inefficient to have to do that everywhere I want to call this function.
View 4 RepliesFor I = 0 To 10
If Items.Count = 0 Then Exit For
Dim T As New Thread(AddressOf Thread)
T.Start(New Object() {"Test", "Test"})
[code]....
When I put same code in empty project it works.
The book "Beginning ASP .NET 4 in VB 2010" contains the following:NOTE: TaxableProduct inherits from Product.You can also cast in the reverse directionfor example, cast a Productreference to a TaxableProduct reference. The trick here is that this
View 2 RepliesPrivate
Sub cmdExit_Click(ByVal
sender As System.Object,
ByVal e
[code]....
I have a method which receives an object as parameter. This object is always of a class I have created, it will never be something simple as string, integer, etc
In my simple example I have created a class called ClassThatWillBeUpdated that requires a type for some reason not shown in the example
Public Class ClassThatWillBeUpdated(Of T)
Private _count As Integer = 0
Public Property Count() As Integer
[Code]....
Or maybe it would be possible to call the DoWork(of T)(item) directly when creating the thread, but as far as I know it's not possible to make a thread run a method that has (of T) as that is basically what I'm looking for
Needless to say, the above code would fail during compile as I have no idea how to do it, if it's even possible. I'm using .net framework 3.5
All I am trying to do is select one school id. Do you know where I went wrong? ty
Public Function findId(ByVal table_name As String, ByVal name As String)
Try
con.ConnectionString = connection_String
[Code]......
unable to cast object of type dataset to type datatable.Dim dataTable As DataTable = DirectCast(dataGrid.DataSource, DataTable)
View 4 RepliesI am trying to check all the childnodes under a parent node, the code I have so far only goes about 2-3 levels deep in the TreeView and I am looking to grab all nodes no matter how deep they are.
Below is the code:
Private Sub CheckChildNode(ByVal currNode As TreeNode)
'set the children check status to the same as the current node
Dim checkStatus As Boolean = currNode.Checked
For Each node As TreeNode In currNode.Nodes
[code]....
i always get this error when i tried to update my table: Unable to cast object of type 'System.Object[]' to type 'System.String[]'.
i only want to update STATUS, ENDTIME, and PRICE
the data type of each field are:
STATUS = nvarchar
ENDTIME = smalldatetime
PRICE = money
[Code]....
"object reference not set to an instance of object" error while creating a new project with visual basic in visual studio.I need to start a new project in visual studio.please respond quickly if u know how to fix this.
View 1 RepliesI using Microsoft.Office.Interop.Excel I get returned a 2D array of type object[,] which contains double for elements. Note that the index lower bound is 1 instead of the default 0, but I can deal with that easily. How can nicely convert the array into double[,] using .NET 3.5. (by nicely I mean concise, or compact).
[Code]...
Is this code you have obtained from elsewhere? Have you tried debugging it line by line? Which line throws the error?
View 2 RepliesI am new in programming with VS2008. Nowdays I try to built a simulation of graphics movement. I use Panel to draw the graphics but I faced a problem when I want to move the object. There were a message
"Unable to cast object of type 'System.EventArgs' to type 'System.Windows.Forms.PaintEventArgs'.".
Public Class Form1
Dim x, y As Integer
Dim n As Integer
Dim xp, yp As Integer
Dim xt, yt As Integer
[Code] .....
I am somewhat new to object oriented programming and am attempting to flatten a Linq object hierarchy by using a shim class.how to initalize a derived class with property values from a base class?I have two objects, a base object with about 100 properties, and a derived object which inherits from the base object and adds a few additional properties beyond those of the base object. My simple constructor creates the derived object, but I am looking for a way to initialize the derived object properties with values from the base object.Right now I am using reflection to iterate over the properties individually and I suspect there may be a better way. The following example shows my shim class constructor for the derived class, and two properties:
newProperty1 - a new string property of the derived class
flattenedProperty2 - a new string property of the derived class, copied from a 2nd-level object of the base class
Code example:
Public Class derivedObj
Inherits baseObj
Private _newProperty1 As String[code].......
Is this the correct constructor approach to flatten the object hierarchy using a shim class? My second question relates to initialization of properties in the derived class. The constructor above creates the derived object, but what is the best way to initialize the derived object properties with values from the base object? The following code uses reflection to iterate over the properties individually, but I suspect there may be a better way.
Code example:
' property names are in the string array fieldNames
'baseObjQuery is an ienumerable of baseObj
'derivedObjList is a list of derivedObj[code].....
Is there a simple way to initialize values for the properties in the derived object based upon the values of the common properties in the base object?
I have created a (kind of) 'Desktop' Form for the main basis of my program. Basically it is made up of 3 panel controls.
1. Holds all buttons which load the different forms (Like the windows start menu when expanded). name: StartMenuPanel
2. Holds Information on log in deatails. name: LogCheckPanel (very thin panel at top of screen)
3. Main panel which takes up the majority of the screen (where I want the forms to load). name: MainPanel
My aim is: When a button is clicked from the 'StartMenuPanel' the form will load with-in the 'MainPanel'.
I tried changing the start position to 'centre parent', but the panels are in the way so some of the childform is overlayed by the panels.
[Code]...
When I run this I get the following error: 'Top-level control cannot be added to a control'.
I hope I've explained this well enough.
In the code base I'm working in there have a method that has the signature
Public Sub SetDropDownValue(Of T As Structure)(ByVal target As ListControl, ByVal value As Nullable(Of T))
The method I am writing is passed a parameter of type object.
How can I cast the object into something that can be passed into the SetDropDownValue method?
I am using reflection to get an object's type, or for this issue an object that has instance properties type, at runtime and then I need to change an existing variable's type into that newly found type. Is this possible? For example, the following code does not work in the line indicated within:
Public Sub DoSomething(x As T, y As T, exp As String)
'This is a instance property on the object of a different type
'i.e. 'T.AnotherType' We need to reflect to find out what type of object
[code].....
How to cast Datagridview.selectedRow(0).databounditem in Object Classes as we do in C#[code]...
View 2 Repliesi am trying to create an sql parameter but i am having an error. it gives me an error like this: Unable to cast object of type 'System.Boolean' to type 'System.Data.SqlClient.SqlParameter'. on all of this line
Dim paramcollection As New List(Of SqlParameter) ' no error on this part but the lines below gives me an error:
paramcollection.Add(New SqlParameter("@CGLCode", SqlDbType.VarChar).Value =
[Code].....
I have do the coding to export the data from DataGridView to Excel. But If am running the code am getting the below error.
[Code]...