C# - Override/Handle Own Type Conversions In .Net
Apr 20, 2011
Is there a way to define an implicit conversion operator in VB.NET?
I can't remember ever seeing or hearing of anyone do this; but now I'm in a situation where I think it would be incredibly useful to define my own custom 'type conversion' for my class.
As an example - let's say I have my own class, 'AwesomeDataManager'. It does not inherit from DataTable, but it holds data in a similar fashion to a DataTable. I would to be able to say, 'myDataTable = CType(MyAwesomeDataManager, DataTable)' and have it execute some code inside my class that would return a populated DataTable.
Granted, I could do something like 'MyAwesomeDataManager.GetDataTable' but for the sake of integrating with an existing code base, I'd like to avoid it.
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Nov 8, 2011
I've got this MustInherit class called ViewerElement, from which derive classes like ViewerLine, ViewerImage, etc.Then, in the main program I have a collection of different elements (Images, Lines, etc.). What I want to do is something like the following:
[Code]...
I'm getting desperate to implement this Clone method without getting errors. How should this be de done?
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Oct 9, 2009
Error1Option Strict On does not allow narrowing in implicit type conversions between method 'Private Sub searchResult_SearchFileMatches(sender As Object, e As Jam.Shell.FileMatchEventArgs)' and delegate 'Delegate Sub EventHandler(sender As Object, e As System.EventArgs)'. on RED Text
[Code]....
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Apr 13, 2012
Consider:
Public MustInherit Class Column
Public ReadOnly Property ReturnSomethingUseful() As Object
Get
'return something useful
[code]....
But this gives the following error:
Public Overrides Function ParseValue(sValue As String) As Boolean'
cannot override 'Public Overridable Function ParseValue(sValue As String) As Object'
because they differ by their return types.
I accept that you can't do this, but I'd like to be able to preserve the semantics of what I'm. trying to do, which is to have an untyped version that deals with Object, but a typed version in derived classes that knows about the specific type T.
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Jan 15, 2009
I created a Class which inherits Combobox and the listview is added . Now what I need is once the user click listview, the listview has to close and the clicked item has to added with combobox text. simply can say combobox1.text = listview.item(0).textFor closing & displaying the listview I need to handle the events. For
My Codings :========Public Class Combu_lstviewInherits ComboBoxPrivate treeViewHost As ToolStripControlHostPrivate Shadows dropdown As ToolStripDropDownPublic mylistview As New ListView
Public Sub New()mylistview.BorderStyle = BorderStyle.Nonemylistview.View = View.Detailsmylistview.HeaderStyle =
[code].....
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Dec 23, 2010
I am working on a new version of my clipboard manager. I was wondering if there would be a way to copy the value of a given handle without knowing its type? The current methods I know require one person to know the type of the handle (as an example by using Marshal.PtrToStructure).
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Apr 11, 2010
I have defined 5 variables T1, T2, T3, T4, T5 As Double and set them all = 0. On a form I have a enter information button. Each time the button is pressed I want to assign a different variable, to a text box input. For instance, If I enter 1 that will become T1, and then if I enter 2 and press the button again, that value becomes T2.
I have tried
If T1 = 0 then
T1 = textbox.text
End if
If T1<>0 And T2 = 0 then
T2 = textbox.text
End if
I have tried to use 'else' statements and all kinds of things like that to no avail. I can get the first two variables correctly assigned but three is impossible with my current understanding. Is there a way to do this, or do I need 5 buttons, so that I can control which variable is assigned? To be correct my intent is to create an observation with three variables each time the button is pressed.
For example, the first button press will result in three variables being assigned a value other than 0; they are T1, B1, and R1. I have just begun to understand the concept of arrays and am wondering if that may be the way to go in this situation. I was just going at this in a newbie way I'm sure and trying to handle each variable type individually, and figure out all the T* variables and move onto the B* variables.
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May 25, 2011
Is it possible to replace these two functions
Function f1 (s As String) As class1()
Dim a() As String = Split(s)
Dim b(UBound(a)) As class1
[code].....
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Feb 23, 2011
I have written some C/C++ code that uses the winapi functions CreateFile WriteFile SetFilePointer etc. to read & write some large (>4 GB) binary files. Some colleagues who are more familier with Visual basic than C, want to modify some of their existing code to call my C code functions.
I have turned my code into DLLs that I have successfully called from other C programs. I have also created a small C DLL that doesn't use the winapi functions & called it from a small VB program.
What I haven't so far been unable to do is pass the HANDLE type variable between a C function that uses the winapi functions & the VB program that call it so the VB can call another of my functions & pass the HANDLE.
In my attempt to do this, the declarations in the header file for two of the functions in the C DLL are:
[Code]...
When I step through the VB code in debug mode there is no problem with calling OpenSegyRW, but at WriteToSegy I get the error message:System.Runtime.InteropServices.MarshalDirectiveException was unhandled
Message=PInvoke restriction: cannot return variants.So what am I doing wrong & is there any way to pass the winapi HANDLE type between VB & C code? BTW indents etc. get lost when I paste my message into the forum. I hope this is decipherable.
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Apr 11, 2012
Is there a way I can catch and handle two different exceptions within the same exception type? For example:
Try
' My code
Catch ex As System.Net.WebException
End Try
I have 2 different exceptions that are System.Net.WebException. I want to handle them different ways. Problem is the catch block above catches them both. Is there a way I can determine if which of the two it is and handle them differently?
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Sep 12, 2009
Say I have a button that creates more buttons with a random .Text property, and placed them on the form in different locations. And since these buttons are being created at runtime, I want to be able to have an event handler for all button controls on the form that makes the form's text the same as the sender's text.
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Jan 10, 2007
I was testing article [URL] to see if I could use this to populate a listview2 with the icons from Directory.GetFiles(apath) and getDirectories. If you go into c:windowssystem32 the program will hang for about 4 mins then if you go back to windows then back to system32 you will get the error.
win32 handle that was passed to icon is not valid or is the wrong type.
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Feb 9, 2009
Write a program to convert a U.S. Customary System length in miles, yards, feet and inches to a. Metric System length in kilometers, meters, and centimeters.
I found this same project on these boards already however I received an error and was seeing if someone could see what I did wrong.
My error message is: 'lstResult' is not declared
Public Class lengthConversion
Private Sub convertBtn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles convertBtn.Click
[Code].....
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Jan 4, 2011
I usually use the developer fusion online code converter to convert code snippets from C# to VB.NET.It partially fails especially in LINQ or complex interface / inheritance scenarios. What are your experiences with other converters? Can you recommend another tool or website?
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Aug 6, 2009
I am rather new to OOP and I have, what may be, a simple question. I am developing an architecture for a project that includes some object inheritence trees. I have been running into a bunch of narrowing conversion issues (the old 'Unable to cast object of type x to x' error). I understand the limitations of narrowing conversions and why this error exists, but I'm not quite sure how to get around it architecturally. Here is an analogous problem to mine...
[Code]...
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Feb 23, 2012
Have been obsessed with DataTypes recently and would like some thoughts, etc. on the following: What's going on is when the BindingSource.PositionChanged Event fires, I capture an Integer relating to another tables Primary Key and then filter that DataTable to select the matching record.
So the focus of the question lies in the first 3 lines in the event. First example creates 2 objects, 2 lines of code. Second example does it all with one line... not sure if it creates only one object or not, seemingly not.. can't tell for sure. Which is "better"? Am I really approaching this from the right angle? Beside y'all here on this forum and Google, I'm self-taught and looking for some validation.
[Code]....
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Mar 18, 2010
Here is my code so far trying to sort the array. The only problem is with Option Strict On, it throws errors on sortedarray(i), and all of the j-1's, j's.Error is dissallows conversions from long to integer
[Code]...
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Jun 17, 2010
Am using VB 2008 OS XP the problem am having is am getting an error Name 'Operators & Conversions' is not Declared , here is the code
[Code]...
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Mar 29, 2010
I am struggling to get this to output calculations correctly. Have I properly made my conversions between decimal,string and so forth. Is that the only reason that a calculation would not produce the right result or is there another reason? I have negative total results for output when they should be positive.
Dim decAmount As Decimal
Dim decInterestRate As Decimal
Dim mdecFutureValue As Decimal
[code]...
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May 7, 2011
i am using integer for days and miles, and the calculation is for money so i am using decimal in one function i am allowed to CDec the days for the calculation and the next function it gives me an error.
I dont see where what i am doing is any different than the other.
Function CalcLodging(ByVal intDays As Integer, ByVal decRoom As Decimal) As Decimal
Return (CDec(intDays)) * decRoom ' This function allows the conversion from integer
End Function
[Code].....
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Jun 12, 2011
Write a program to convert a U.S. Customary System length in miles, yards, feet and inches to a. Metric System length in kilometers, meters, and centimeters.My error message is: 'lstResult' is not declared
Public Class lengthConversion
Private Sub convertBtn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles convertBtn.Click
Dim miles, yards, feet, inches As Double
[code]....
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Feb 22, 2010
How do I correct the error Option Strict On disallows implicit conversions from 'Double' to 'Integer'. ?
The two lines below that divide by 2 are causing the error.
Private Function StringToByteArray(ByVal hex As String) As Byte()
Dim NumberChars As Int16 = CShort(hex.Length)
Dim bytes As Byte()
Dim i As Integer = 0
bytes = New Byte(NumberChars / 2) {}
[Code]...
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Sep 2, 2009
Dim I As Integer
Dim iCount As Integer
Dim clrHashForeColor As Object
Dim clrHashBackColor As Object
cbotifcompression.Items.Add("LZW")
[Code].....
I get the error for both highlighted red parts = Option Strict On disallows implicit conversions from 'Integer' to 'Short'.
Also
I get = Option Strict On disallows operands of type Object for operator '='. Use the 'Is' operator to test for object identity.
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Jul 5, 2011
I have an error in my VB.net program - I have tried various casts etc but it just will not resolve the issue - so reluctantly I post it here to see if anyone else has a similar problem.
Error 1 Option Strict On disallows implicit conversions from 'Object' to 'String'.
Private DS As New DataSet ' Languages
Function TransTxt(ByVal Frm As String, ByVal Item As String) As String
[Code]...
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Apr 6, 2009
I get "Option Strict On disallows implicit conversions from 'Object' to 'ExpTreeLib.CShItem'.", which is a listview that I have on my form, which references expTreeLib.dll
[Code]...
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Mar 20, 2010
i have this error what i have to change in the code?
TextBox65.Text = Math.Abs(CInt(Val(oddTextBox54.Text))) / Math.Abs(CInt(Val(TextBox56.Text))).ToString()
Error11Option Strict On disallows implicit conversions from 'String' to 'Double'.
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Mar 4, 2010
how i have to write this variable not to have errors
Dim divider As Integer = (20 / 3)
Error 1 Option Strict On disallows implicit conversions from 'Double' to 'Integer'
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May 20, 2011
[Code]...
How do I convert this proper? (Option Strict On)
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Mar 23, 2009
I wrote an application to handle a joystick with directinput. It works fine if it uses the handle of the main window but it doesnt happen the same if the handle is the one of the component that contains the joystick's operation.
I mean:
main form handle: 15
component handle (which is inside the window and the joystick needs the focus of this component to work): 25
It always work if the handle i initilizate the device is the main form (15).How can i use only the handle of the component?
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May 6, 2009
When I have Option Strict ON in my project, the IDE tells me that "Option Strict On disallows implicit conversions from 'System.Data.ParameterDirection' to 'String'." How can this be, since I'm using their built-in enumeration for the SqlParameter direction.
[Code]...
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