VB Inheritance And Narrowing Conversions
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...
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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
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Apr 5, 2011
Below is example code of what I want to do:
Public Class Test
Sub New()
Dim cool As New B
cool.Doit()
[code]....
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Dec 1, 2009
VB.Net just showing its true colors again? When I turn Option Strict On, I am still able to do implicit narrowing conversions in a for each loop.For example, this code actually compiles;
Private Sub foobar()
Dim foo() As foo = {New foo}
For Each bar As bar In foo[code].....
From my understanding of Option Strict, this should not work.See here "Restricts implicit data type conversions to only widening conversions".My code above is a narrowing conversion, and so should be illegal.It will fail at runtime with an InvalidCastException.
C# does the same thing. Below is another implicit narrowing conversion.
private void foobar()
{
foo[] foo={new foo()};[code]......
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Jul 18, 2011
Here is my function:
[Code]...
I understand the error but am not sure how to fix it, how do I tell it which one I am using? On msdn it says to ignore this error turn Option Strict to Off, but it is already off. It's not showing up as an error in the error list at the bottom, just a red underline, but it is preventing me from continuing with .OrderBy() and anymore functions.
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Sep 3, 2009
After running into much difficulty getting started on my little planner attachment, I found this C# program (calendar_src) floating around on the net...somewhere. So I have been working on trying to convert this from C# to VB, which I have been using an online converter. From what I know I have been going through and trying to edit the code after it has been converted to VB code as best as I can. But now I have limited the errors from over 50 to these:
Error1Overload resolution failed because no accessible 'DrawLine' can be called without a narrowing conversion:
'Public Sub DrawLine(pen As System.Drawing.Pen, x1 As Integer, y1 As Integer, x2 As Integer, y2 As Integer)': Argument matching parameter 'y1' narrows from 'Double' to 'Integer'.
[code].....
Not only this, the VB main Form1 isn't showing the "DayView1" control that the C# one is. When I first created the VB app, I didn't know how to make 2 projects in 1, so it's probably wrong altogether...but I tried. The only reasons I am wanting to go off of someone else's control is because it only lacks 1 feature that I want, and that's having a full month view, not just limited to 1-3-5-7 day views.
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Sep 11, 2010
I have a little problem here. I am getting an error which they are jumping on this statement: a.Proxy = New WebProxy(Address.Text, Ports.Text). I have removed the equal to replace with the Address.Text and Ports.Text, I have tried to included And statement and the '&' in that statement, but I keep get the messagebox. The ip I am connecting are working well.
Here it is the
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Try
Dim a As HttpWebRequest = DirectCast(HttpWebRequest.Create("http://whatismyip.com/automation/n09230945.asp"), HttpWebRequest)
[code]....
Error: Overload resolution failed because no accessible 'New' can be called without a narrowing conversion: 'Public Sub New(Address As String, BypassOnLocal As Boolean)': Argument matching parameter 'BypassOnLocal' narrows from 'String' to 'Boolean'. 'Public Sub New(Host As String, Port As Integer)': Argument matching parameter 'Port' narrows from 'String' to 'Integer'.
I shouldn't have the messagebox displaying on my screen while I am connect to the ip. I have tried with the dim statement to included the textbox strings, but it doesn't help. how I could included the strings of the textbox in the a.Proxy = New WebProxy statement?
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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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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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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.
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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
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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
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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
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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
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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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Apr 12, 2010
I am getting Error at this line m_frmPrintPreview.vspPrint.Font = New Font(Me.m_frmPrintPreview.vspPrint.Font,FontStyle.Underline) Error is Overload resolution failed because no accessible 'New' can be called without a narrowing conversion: 'Public Sub New(familyName As String, emSize As Single)': Argument matching parameter 'familyName' narrows from 'stdole.IFontDisp' to 'String'.
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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) {}
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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")
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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
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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
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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
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How do I convert this proper? (Option Strict On)
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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.
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Apr 22, 2012
i am just trying to apply inheritance ..Below is my Code ... on which i am not getting the output on my Text_Box ... when in write it in a Child Class
Imports System
Imports System.Windows
Imports System.Windows.Forms
[code]....
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Jul 14, 2011
Has someone a hint what I'm doing wrong in VB.Net?
Module Module1
Interface ISearch(Of T As ISearchResult)
Function ids() As List(Of T)
End Interface
[CODE]...
The third cast isn't working. Why? did I miss a oop lesson?
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Mar 2, 2011
What's the choice design that microsoft do that? Of course, as of me, I don't use inheritance a lot, or at all.
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Oct 21, 2011
we have 3 classes:Class S, class A, class B / A and B inherits S.A has a property A1 and B has a property B1.we also have a collection of objects that has A and B objects.ex.
Dim c as Collection = new Collection
c.add(new A)
c.add(new B)
Now we want to make a general object that will read from the collection.
ex .
Dim obj as S
how can we cast obj in order to see properties A1 or B1 according to the class;
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Apr 20, 2011
Form1
Public Class Form1
Private Sub But_Bell_Click(sender As System.Object, e As System.EventArgs) Handles But_Bell.Click
MessageBox.Show("Ding a ling")
End Sub
[code]....
Where has the whistle button gone? The class part of the inheritance has works because you can access it via code.
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