C# - Inheriting From System.ValueType?
Jan 30, 2012Am I correct in believing that any object that doesn't inherit from System.ValueType must therefore by definition be a reference type?
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Using Inheritance-Based Controls - Creating As New Classes (not UserControls) Inheriting From An Existing System Control
Oct 15, 2011I seem to be having a problem with controls that I am creating as new classes (not UserControls) inheriting from an existing system control. Everything seems ok while I create the control code, through to the compile (which is successful and adds the control to the toolbox) and dragging the control from the toolbox to the GUI surface. However, when I then debug or compile the project, I get a message such
[Code]...
Pass A Nullable Valuetype Into A Non Nullable Valuetype?
Sep 17, 2009I accidently wrote some code today that was like this[code]...
I immediately noticed the issue, but I had already hit the run button. It compiled successfully, I ran it through to the section and it threw an exception.
You can't do this in C#, it gives a compile error "cannot convert from 'int?' to 'int'".
Is there an 'Option Explicit' type switch that I can turn on to ensure that this sort of error does not occur again?
Create A Custom Exception Without Inheriting System.Exception?
Dec 26, 2009Is there anyway to create a Custom Exception without inheriting System.Exception?
my reason is that they have a lot of methods which i do not wish my Class to have.
.net - Can't Set 'Value' Of A Custom ValueType?
Apr 30, 2012I have created a custom ValueType:
Private Structure MyValueType
Private _integerValue As Integer
Public Sub New(initValue As Integer)
[code]....
But I can't work out how I can test the value such as this:
Dim v As New MyValueType(3)
Dim x As New MyValueType(4)
[code]....
Error:Operator '=' is not defined for Types MyValueType and MyValueType
So how do I define Operators for my ValueType (I know this must be simple but I can't find an exmaple anywhere!)?Note I don't want to test If v.Equals(x)
How To Constrain To A ValueType
Jun 22, 2011I've just spotted this thread:>> [URL] Here is a C# article on the subject:>> [URL] how to constrain to a ValueType?
I,E:
Public Class ExampleClass(Of T As System.ValueType)
End Class
Valuetype Of 1d Array Cannot Be Converted From X To Y
Oct 15, 2009I attempting to implement the Addemar Web Service (e-marketing system) into my VB.NET application. I've managed to get a connection and called a simple method, returning a array of field id's that is. I get into truble when I want to return the label of that particular id.Value of type '1-dimensional array of WindowsApplication1.AddemarWS.NamedValue' cannot be converted to 'WindowsApplication1.AddemarWS.NamedValue'.
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.net - Get MinValue / MaxValue Of A Certain ValueType Via Reflection?
Mar 31, 2010I need to this at runtime. I checked using Reflector and value types line like Int16, for example, should contain
[Code]...
EDIT: only for the example I used directly GetType(UInt16) but in real code this part is substituted by an instance of unknown-at-design-time .NET Type
Convert A String To Generic Type T When T Is A Valuetype?
May 1, 2012fast way in VB to go from a string to a generic type T constrained to a valuetype (Of T as Structure), when I know that T will always be some number type?This is too slow for my taste:
Return DirectCast(Convert.ChangeType(myStr, GetType(T)), T)
But it seems to be the only sane method of getting from a String --> T. I've tried using Reflector to see how Convert.ChangeType works, and while I can convert from the String to a given number type via a hacked-up version of that code, I have no idea how to jam that type back into T so it can be returned.
I'll add that part of the speed penalty I'm seeing (in a timing loop) is because the return value is getting assigned to a Nullable(Of T) value. If I strongly-type my class for a specific number type (i.e., UInt16), then I can vastly increase the performance, but then the class would need to be duplicated for each numeric type that I use.
It'd almost be nice if there was converter to/from T while working on it in a generic method/class. Maybe there is and I'm oblivious to its existence?
Conclusion:Testing the three provided implementations below and my original DirectCast/ChangeType form, @peenut's approach of using a prepared delegate to fetch the Parse method from a basic type works. No error checking is done, however, so implementors need to remember to only use this with valuetypes that have a Parse method available. Or extend the below to do error checking.
All runs were done on a 32bit system running Windows Server 2003 R2 with 4GB of RAM. Each "run" is 1,000,000 executions (ops) of the method to be tested, timed with StopWatch and reported back in milliseconds.
Original DirectCast(Convert.ChangeType(myStr, GetType(T)), T):
1000000 ops: 597ms
Average of 1000000 ops over 10 runs: 472ms
Average of 1000000 ops over 10 runs: 458ms
[code]....
Comparatively, peenut's approach is almost 200ms faster when executed 1,000,000 times in a tight loop, so his approach wins out.
Main Difference Between A Class And A Type And A ValueType
Dec 17, 2009what's the main difference between a Class and a Type and a ValueType.and is a Delegate a Type? or an eventhandler/event (the actual event itself)is every object a type? or is it only true in VB
View 3 Replies.net - Faster Way To Convert From A String To Generic Type T When T Is A Valuetype?
Jan 6, 2011Does anyone know of a fast way in VB to go from a string to a generic type T constrained to a valuetype (Of T as Structure), when I know that T will always be some number type?This is too slow for my taste:
Return DirectCast(Convert.ChangeType(myStr, GetType(T)), T)
But it seems to be the only sane method of getting from a String --> T. I've tried using Reflector to see how Convert.ChangeType works, and while I can convert from the String to a given number type via a hacked-up version of that code, I have no idea how to jam that type back into T so it can be returned.
I'll add that part of the speed penalty I'm seeing (in a timing loop) is because the return value is getting assigned to a Nullable(Of T) value. If I strongly-type my class for a specific number type (i.e., UInt16), then I can vastly increase the performance, but then the class would need to be duplicated for each numeric type that I use.
It'd almost be nice if there was converter to/from T while working on it in a generic method/class. Maybe there is and I'm oblivious to its existence?
Conclusion:Testing the three provided implementations below and my original DirectCast/ChangeType form, @peenut's approach of using a prepared delegate to fetch the Parse method from a basic type works. No error checking is done, however, so implementors need to remember to only use this with valuetypes that have a Parse method available. Or extend the below to do error checking.
All runs were done on a 32bit system running Windows Server 2003 R2 with 4GB of RAM. Each "run" is 1,000,000 executions (ops) of the method to be tested, timed with StopWatch and reported back in milliseconds.
Original DirectCast(Convert.ChangeType(myStr, GetType(T)), T):
1000000 ops: 597ms
Average of 1000000 ops over 10 runs: 472ms
Average of 1000000 ops over 10 runs: 458ms
[code]....
Using System.Reflection and calling InvokeMethod to get at the Parse method:
1000000 ops: 12213ms
Average of 1000000 ops over 10 runs: 11468ms
Average of 1000000 ops over 10 runs: 11509ms
Average of 1000000 ops over 10 runs: 11524ms
[code]....
Konrad's approach to generate IL code to access the Parse method and store the call into a delegate:
1000000 ops: 352ms
Average of 1000000 ops over 10 runs: 316ms
Average of 1000000 ops over 10 runs: 315ms
[code]....
peenut's approach of using a delegate to access the Parse method directly:
1000000 ops: 272ms
Average of 1000000 ops over 10 runs: 272ms
Average of 1000000 ops over 10 runs: 275ms
[code]....
Comparatively, peenut's approach is almost 200ms faster when executed 1,000,000 times in a tight loop, so his approach wins out. Although, Konrad's wasn't far behind and is itself a fascinating study of things like ILGenerator.
Get Name Of Inheriting Class?
Apr 17, 2009In the below mockup, how do I find out, if I am an instance of FooDAL or WeeDAL from within the method DoMagix()?
Public MustInherit Class DataAccessClass
Public Sub DoMagix()
'** LOOK AT ME!!! **
[code].....
.net - Inheriting From List(of T) Class
Apr 27, 2009I want to implement a priority queue class. When an item is added at a higher priority it is pushed to the front of the queue instead adding to the end of queue. Simple few lines of code
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Forms Inheriting From A Class?
Jul 3, 2010I've created a class called connector. By clicking on project and adding a class.And I want to inherit from that class in the forms But I get this error.
Base class '<baseclassname1>' specified for class '<partialclassname>' cannot be different from the base class '<baseclassname2>' of one of its other partial types`
what do I do?Here's the class named connect.vb:Imports MySql.Data.MySqlClient
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Inheriting Classes + Its Constructors?
Nov 2, 2009i've got a class called prob that inherits system.exception however it seems not to have inherited the constructor
Public Class prob
Inherits System.Exception
public sub stuff
[code]....
throw new exception("test") 'works Throw New prob("test") 'doesn't work is it possible to inherit the constructor into my class prob as well?
VS 2005 - Inheriting Forms Within An .exe ?
Apr 1, 2010I have an .exe project with a form in it that I want to use as a base class for other forms in the project. So I try to add a new inherited form to the project, but it says "Warning: No build assemblies contain components to inherit from. Build the current application, or click Browse and select a previously built assembly from another application". My base class is declared public and my exe has been built. I don't understand. Can you only do form inheritance in a dll?
View 1 RepliesVS 2010 Inheriting From ListBox?
Apr 6, 2012I have a custom control type that inherits from ListBox. It is a list box where you can assign a ContextMenuStrip to each individual item, stored in a Dictionary object. To do this I also had to create a helper class that inherits from ObjectCollection to make sure the owning ListBox gets notified whenever an item is added or removed from the collection, so the corresponding entry in the dictionary can be removed.Now I have a problem that baffles me: Whenever I right click an entry in my EnhancedListBox, I get the following error on the line that has been marked red in the "InvalidArgument=Value of '1' is not valid for 'SelectedIndex'."(Of course, the value can be 0 or 2 as well, depending on which item in the list I click.)
I have checked, and there are 3 objects in the collection, in fact the current value of SelectedIndex was 1. The quotes are also misleading, the value I am trying to assign if of type integer, as is the current value of SelectedIndex.
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VS 2010 Inheriting XML Comments
Apr 20, 2010I have a MustInherit class, let's call it BaseClass, with a bunch of MustOverride ReadOnly properties. The user is supposed to inherit this class and override the properties, returning appropriate values.To help the user decide which property does what, I have included XML comments for each property, so the BaseClass looks like this [code]I now want to enable the user to inherit this class (DerivedClass1) instead, so that he can, for example, override only the Name property, and leave the other properties untouched. This way, he can create a slight modification to one of the default classes, instead of having to rewrite it completely (in reality, there are loads more properties). There are no XML comments, because they are in the BaseClass, and not in the DerivedClass1, which is the class I'm inheriting. In other words: the XML comments are not 'inherited'.Do I really have to copy/paste all the XML comments from the BaseClass and put them in the DerivedClass1 too? Or can I somehow tell the DerivedClass1 to use the XML comments from its base class?
View 1 RepliesIIS 7.5 Web Application Inheriting From Parent Web.config
Sep 27, 2010Well the title says it all im using a asp.net 4.0 project.My file structure looks like this [code]Now the WebService seems to get some parts of the web.config from the RootSite, the problem here is <configuration><system.webServer>..So i tryed to place this around that section <location path="." inheritInChildApplications="false"> but that had the result of making a httpHandler only to function in the root directory.So is there any solution to this? i don't understand why my webservice's web.config is inheriting from the root's web.config..
View 1 RepliesAsp.net - Inheriting From DataSourceControl Does Not Produce An IDataSource
Feb 15, 2010I am trying to create a custom datasource control.
I have been following this article to the letter (I think...).
I have a skeleton / basic implementation of my datasource, however when I declare it in the markup and try to statically bind it to a gridview, I receive the following error:
The DataSourceID of 'grdVw' must be the ID of a control of type IDataSource
This seems extremely strange to me, since my datasource inherits from DataSourceControl, which in turn implements IDataSource. Even if I explicitly implement IDataSource in my custom datasource, it makes no difference.
My Markup is:
<DataBrokerDataSource ID="objSrcDBroker" runat="server" />
<div>
<asp:GridView ID="grdVw" DataSourceID="objSrcDBroker" DataMember="Table0" runat="server">
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Inheriting From A Custom User Control
Oct 28, 2011I have a component class that inherits a user control class and i'm trying to inherit from that same class in a new class.public class B inherits class Unfortunately, I get an error pointing to the .g.vb file saying:Base class 'System.Windows.Controls.UserControl' specified for class '...' cannot be different from the base class '...' of one of its other partial types When I swap the "Inherits System.Windows.Controls.UserControl" with inherits from the base class in .vb files the program compiles but when I try to access any of the components I get an error saying "Object reference not set to an instance of an object."Why is it doing this? it's as if the my sub class isn't inheritingUserControl method at all.
View 2 RepliesInheriting From Controls That Use Embedded Resources
Apr 30, 2009I'm having some trouble trying to inherit a control that uses an embedded resource. The trouble is - this control uses me.GetType() instead of GetType(ControlName). Now when I try to use the derived control, it looks for the resources in the derived control's assembly, instead of the base control assembly, and obviously - doesn't find them.
View 1 RepliesInheriting Shared Variables/properties?
Nov 29, 2009basically i was wondering if we could inherit shared variables but restrict its scope to only that of the class itself.
Class A
Public Shared shared_variable as Boolean = true
End Class
[code]....
when i do this A.shared_variable = False, B's shared_variable also becomes false. how do i stop this?i cannot remove the Shared keyword because shared_variable should be able to be accessed without an instance of the class?
Superclass Access To Inheriting Class?
Dec 19, 2009I have 2 business classes, user & salutation and 2 DAL classes of the same name.
The business classes both have properties of the data class E.g.
Public Property Data() As Data.Salutation
Get
Return _Data
[Code].....
To access some data, you would do Business.Salutation.Data.SalutationID
Both busines classes inherit from BaseClass which contains all my database access methods.
Is there a way that I can access the Data property of the inheriting classes from the BaseClass?
I assume I will need to use reflection as the property types will always be different.
[vb2010]make Inheriting Forms?
Feb 13, 2012I have created a Windows Form inherited from an existing form using the Inheritance Picker: Project menu ==> Add Inherited Form.So now I have the Form-base (FrmP1) and the inherited form (FrmP2)The form works perfectly. If I open the "code" window of FrmP2 I can see only the main class:
Public Class FrmP2
End Class
I have added now a FormClosed event in P2:
[code].....
Difference Between Inheriting And Creating Object Of A Class?
Jun 29, 2010When we can access the public methods via object then why is there need of inheritance.
View 2 RepliesInheriting A Class With Useful Methods Or A Creating A Module?
Nov 27, 2009What is neater / better in your opinion? Inheriting a Class with useful methods or a creating a module?
For example:
vb Module Tools_Module
Public Sub Print(ByRef text As String)
Console.WriteLine(text)
End Sub
End Module
[Code]...
Inheriting Forms - Expose Control Events?
Nov 2, 2009I am using an inherited form extensively for the first time, and I'd like to know if what I'm doing is correct.I have a base form with a grid and four buttons (Add, Edit, Remove and Close). There is no functionality in any of the button click events, as the specific implementation of each derived form will be different. The only exception perhaps is that the Close button closes the form. The only reason I am using a base form really is because I've many forms that look the same.How do I now expose the button click events to any derived forms? The only straightforward way I could think of was to have the button click events call an Overridable method, which I then override in the derived form:
Public Class frmTableBase
Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
Me.AddButtonClicked()[code]...
Is that the correct way? It seems a little bit overkill to have to do this, although I can't think of another way really... Perhaps I could add the Overridable keyword to the event handlers themselves (and make them public)..?I'm doing it the way I showed now however. It works, but I'd just like to know if this is the generally accepted way of doing this.
VS 2008 Inheriting Web Client To Add A Timeout Property?
May 18, 2009VS 2008
I am not sure how much work there is to inheriting from the web client class.
Currently I am using it in my project. And I can't change to anything else. The customer would like to have a timeout after a certain period of time. The web client doesn't have this.
So rather than re-invent the wheel, I am thinking of inheriting from the web client and adding this property.
.net - Inheriting A VB Class In C# And Overriding Constructors That Take Optional Parameters?
Jan 12, 2010Most of our code base is in VB.NET. I'm developing a project in C# that uses a lot of the assemblies from the VB.NET code.There are three relevant classes in VB.NET:
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