VS 2010 Casting Between Derived Types Throws InvalidCastException?
Dec 14, 2010
The following Code throws the InvalidCastException error. What I wish to know is why and what the standard workaround is for this situation.
Module Module1
Interface IFooBar
End Interface
Class Foo : Implements IFooBar
Public Shared Widening Operator CType(ByVal Val As Foo) As Bar
Return New Bar
[Code]...
What I would like is the line B = C to work without me having to know what type of object C currently is. I need to find a way to get this to work so that i can finish a function I ma working on so that it will excecute correctly on any new object which implements the interface and boasts an Operator CType function to cast it to the type used in the function.
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Apr 20, 2010
Public Function CastToT(Of T)(ByVal GenericType(Of Object) data) As GenericType(Of T)Return DirectCast(data, GenericType(Of T))End Function
The above clearly does not work. Is there any way to perform this cast if I know that all objects inside data are in fact of Type T?
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Nov 19, 2010
Consider this examlpe
Interface IInterface
Property MyProperty
End Interface
Class MyClassy : Implements IInterface
[code]....
The type of sender in the above example is of type MyClassy5.Is there any performance differences between the two types of casting?
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Jun 29, 2010
I'm wrestling with this treeview control. I have extended the TreeNode class to attach some extra data to the node. Basically, I added one property:[code]Is there a way to cast from a base type to a derived type?
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Dec 25, 2009
I do have a customized treeView which inherits from treeview and uses customized treenodes which inherit from treenode. It works, but each inherited method of the treeview using a treenode as a parameter forces me to do an explizit cast from treenode to my customized treenode to access the additional functionalitiy of my treenode class.
Is there a general way to avoid explizit casting all day long? E.g. telling my customized treeview that all it's properties, mehthods, etc. from now on are working with my customized treenodes instead the general treenode as default?
Turning off option strict is not an option because I want to keep this. Overriding each method, etc. is to cumbersome.
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Aug 1, 2011
Apparently, this is not allowed? Is there a way to cast to an UInt16?
zero2 = CUInt16((Ch1OutputResults.range10Zero - 0) * 65535)
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Dec 10, 2011
I use this code to populate combobox1&2:
'Main form on load events
Private Sub frm_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
[Code]....
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Apr 20, 2011
I'm trying to compile a brand new 2010 windows forms application with a form and a single button that should display a msgbox with "hello" in it.When I try to compile I get the error message:
Unable to write to output file <filename>: This implementation is not part of the Windows Platform FIPS validated cryptographic algorithms.
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Feb 18, 2011
When i use my UserControl in a project my Mouse Enter & Leave events aren't firing, i assume i fix this with a raiseevents in my usercontrol. However when i try to do this it says something about "cannot raise base event from derived class".
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Jun 27, 2011
Basically I have a system that will take an unknown structure (that should be marked serializable) and attempt to serialize it to a stream. However, before the system will do that, I want to know if there's a way to check every single variable/property to make sure that all the types are serializable.Anyone know a way?
EDIT: For now, I was able to do this:
Private Function IsSerializable(ByVal obj As [Object]) As [Boolean]
If obj.GetType.IsSerializable Then
[code].....
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Nov 1, 2009
I have a class with a Property called 'Value' which is of type Object.Value can be of any type, a structure, a class, an array, IList etc.My problem is with the setter and determining whether the value has changed or not.This is simple enough for value types, but reference types and lists present a problem.For a class, would you assume that the Equals method has been implemented correctly, or just assume that the value has changed every time the setter is called?If I did assume it's changed, then perhaps I should assume it for value types as well, so that the behaviour is consistent.
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Sep 28, 2011
I've been following this article:and have everything working.Under the Support for Custom Types section, it introduces a collapsable type for the spell check options. The option are added together to produce a string that is displayed in the grid in the Spell Check Options row. Is it possible to get this string directly from the 'AppSettings' class or do I need to add another property and copy the code from the ConvertTo and ConvertFrom functions?
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May 9, 2010
I have a form with four chart controls on it and i would like to count them at runtime but i'm hitting a snag.
For Each ctrl As Control In Me.Controls
If TypeOf ctrl Is System.Windows.Forms.DataVisualization.Charting.Chart Then
Label1.Text = ctrl.Controls.Count
End If
Next
the count is returning zero when it should be returning 4 - what am i missing?
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Sep 29, 2010
I freely admit that I tend to avoid using API calls as much as possible I wish to use this API call
[Code]...
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May 7, 2011
I'm having a bit of an issue with this program I have been working on for my class. It's a future values calculator, that takes a single data type, decimal data type and a integer data type does the formula and then spits back out the Future value. What i'm having difficulty with is converting the string over.
Public Class Form1
'Define the Module level variables
Dim FutureValueInteger As Integer
[Code]....
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Apr 27, 2011
I am using Visual Studio 2010 Prof. In C# I can create my own Enumerator and use it like this:MyEnum value = Now, Intellisense will suggest a value of MyEnum. In VB, when I write:Dim value As MyEnum = I get a huge list of every types. When starting to write my enumerator value (could be a word like "sunny") it filters out some types but I would like to have it like in C#. Anyway I will use the MyEnum type and no "String nor Objecte nor IntPtr...".
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Jan 20, 2011
In Vb6 you could make a private type by doing the following:
Private Type PointAPI
X As Integer
y As Integer
End Type
Vb.Net doesn't support this. I need it to store the x and y position of a certain pixel. I know i could just declare an x and y variable but i would rather use something like:
xyCentre.X = 5
xyCentre.Y = 10
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Apr 27, 2012
I want to design a application which can support two different types of databases same time e.g; when we install, it will ask which db it has to support and based on initial selection it should work with any db without changing anything in the application.In short it has to be developed keeping in mind that user may have either MS SQL or MySQL. It should support both.
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Mar 4, 2012
First post here so Im sorry if im posting in the wrong place. Im trying to build a simple poker game which requires the program to recognise hands of each players. Luckily there are 3rd party solutions such as pokereval. However my problem comes when i try to convert a C# ported version of pokereval by Keith Rule, into vb.net. The following error shows up referring to the line with the *.
[Code]...
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Mar 14, 2012
I am trying to convert a piece of C# code, and I ran it through a converter, and had to make some changes.I am now running into this error:
Operator '<<' is not defined for types 'Char' and 'Integer'
The code is:
a += CType(URL(k + 0) + (URL(k + 1) << 8) + (URL(k + 2) << 16) + (URL(k + 3) << 24), UInt32)
b += CType(URL(k + 4) + (URL(k + 5) << 8) + (URL(k + 6) << 16) + (URL(k + 7) << 24), UInt32)
c += CType(URL(k + 8) + (URL(k + 9) << 8) + (URL(k + 10) << 16) + (URL(k + 11) << 24), UInt32)
The error occurs on each of the (URL(...) << X)
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Oct 8, 2009
I have an issue with Visual Studio's support for coloring User Types in VB.NET, I'm an C# developer that have been forced to code in Vb.NET by political rules in my organization, and I really misses the support for coloring user types in Vb.NET, I had hoped that this would be solved in Visual Studio 2010 and well in the beta they have added Vb.NET User Type coloring, but the coloring is the same for all user types I cant't have one color for interfaces and one for classes and so on.
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Jul 20, 2011
Imports System.IO
Public Class Form3
Const IMAGE_DIRECTORY As String = "C:images"
Dim files As String() = Directory.GetFiles(IMAGE_DIRECTORY)
Dim max_length, i As Integer
Dim s, fname As String
[Code]...
I simply want to have a list of all graphics saved in specified folder displayed as miniatures - this suppose to be a sort of an image browser - it does not have to be done using ListView, so I'm open to any suggestions.
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Jun 23, 2012
I need to compare two dictionary values if the types stored are equal, this is what i have
if gettype(Args(key)) = gettype(argtypes(key)) then
'' do something
end if
[Code]....
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Aug 26, 2011
I am trying to follow this thread
[URL]
and I have it pretty close but have one error.
Quote:Handles clause requires a WithEvents variable defined in the containing type or one of its base types.
That error is on both of these, in blue
Private Sub SpellChecker1_DeletedWord(ByVal sender As Object, ByVal e As NetSpell.SpellChecker.SpellingEventArgs) Handles SpellChecker1.DeletedWord
'save existing selecting
[code]....
I have added the reference, I have also added them to the toolbox. My dictionary is all set. What did I miss?
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Mar 19, 2010
I use to set WithEvents variables to Nothing in Destuctor, because this will "Remove" all the Handlers associated with Handles keyword. Will this have the same effect for derivated classes?
[Code]...
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Apr 26, 2009
I have a base class where amongst other code I have declared 2 properties. In my derived class, I get data from the DB and assign the results to the base class properties. This is so when I go back to the base class code, I can access the property values. It allows me to set the values in the derived class but once I go back to the Base class, the values don't exist.
[Code]...
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Apr 4, 2012
Dim CustID As String = txtSrchCustID.Text
Dim FirstName As String = txtNewCustFName.Text
Dim SecondName As String = txtNewCustSName.Text
If CustID And FirstName And SecondName = "" Then
MsgBox("Please enter a term to search by")
EndIf
This returns "Conversion from string "" to type 'Long' is not valid." I was wondering what the error is and how it's possible to fix it? The other questions that I've looked at were mostly to do with variables assigned incorrect types, but I think that isn't the issue. It occurs when all of the variables are empty.
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Oct 30, 2009
OK, this is going better, now im stuck in the mud again, i am trying to get a form to print,this works now, however i would like to enable a few frames with text boxes for a few seconds to allow the printer to print the text in black instead of gray. he error i am getting is this, as the timer disables:" Unable to cast object of type System.Windows.Forms.Timer' to type 'System.Windows.Forms.ToolStripMenuItem'. "
Public
Sub
Print_Renamed_Click(ByVal
[code].....
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Apr 9, 2010
I have a field named 'UserID' in my OLE database with the type 'Autonumber'. But when I try to cast it to a variable of type 'String' I get an an InvalidCastException - Specified cast is not value.
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May 15, 2011
Private Sub gvDesignGVnote_CellClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles gvDesignGVnote.CellClick
If e.RowIndex < 0 Then[code]......
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