.net - Multi-level Inheritance With Implements On Properties?
Jun 18, 2010
Let's say I have 2 interfaces defined like so:
public interface ISkuItem
{
public string SKU { get; set; }
}
[Code]....
VB.NET explicitly requires you to add Implements IInterfaceName.PropertyName after each property that gets implemented whereas C# simply uses regions to indicate which properties and methods belong to the interface.
Interestingly in VB.NET, on the SKU property, I can specify either Implements ISkuItem.SKU or Implements ICartItem.SKU. Although the template built by VS defaults to ISkuItem, I can also specify ICartItem if I want. Oddly, because C# only uses regions to block out inherited properties, it seems that I can't explicitly specify the implementing interface of SKU in C# like I can in VB.NET.
My question is: Is there any importance behind being able to specify one interface or another to implement properites in VB.NET, and if so, is there a way to mimic this functionality in C#? Furthermore, what is the effect of specifying one interface over another when implementing properites?
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Jun 18, 2010
This question is a follow-up to my last question with a reference to COM Interop. Let's say I have the following 2 interfaces and implementing classes:
[Code]...
Interfaces are important in COM interop for exposing properties and methods to IntelliSense in the VB6 IDE (per this article). However, because ICartItem is inherited from ISkuItem, SKU is not explicitly defined in ICartItem and thus is not visible in IntelliSense in VB6 and even throws a compiler error when trying to write to objCartItem.SKU.
I've tried using Shadows and Overloads on the SKU property in ISkuItem, but then the compiler wants me to explicitly implement SKU for both ISkuItem and ICartItem within the CartItem class. I don't think that's what I want. Is there a way (in either VB.NET or C#) to explicitly declare the SKU property in ICartItem without having to declare SKU twice in the CartItem class?
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Aug 13, 2011
I can create a Custom UserControl with simple properties (Integer, String, etc) and have those properties show up in the Property Panel. I can also create a Custom UserControl with properties like Size, Rectangle, etc and the properties will show up as an expandable item in the Property Panel (click on the '+' and the Size expands to Width & Height).
Is it possible to create properties with my own custom structure? e.g. Property 'Message' expands to Text, ForeColor, BackColor, Blink etc. I have tried creating a property that references a simple class or structure with containing the properties representing my custom structure but in the Property Panel the property is greyed out and cannot be expanded or modified.
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Jun 7, 2010
When I write the following statement in VB.Net (C# is my normal language), I get an "end of statement expected" referring to the "Implements" statement.
<Serializable()> _
<XmlSchemaProvider("EtgSchema")> _
Public Class SerializeableEntity(Of T As {Class, ISerializable, New}) _
Implements IXmlSerializable, ISerializable
...
End Class
The C# version that I'm trying to emulate is:
[Serializable]
[XmlSchemaProvider("MySchema")]
public class SerializableEntity<T> : IXmlSerializable, ISerializable where T : class, new()
{
....
}
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Apr 19, 2012
I've got a form with a listbox on it.In a second form I inherit the complete first form. But when I try to use that listbox in the second form with e.g.Index = LstWoodshop.FindString (Order(0))(where LstWoodshop is that inherited Listbox) I get the error message:'LstWood shop' is not declared. It may be inaccessible due to its protection level.What or where can I change this setting so that this listbox on form 1 is also available/accessible on form 2?
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Apr 6, 2010
In my first application I need to create a multi-level "IF" statement and I am a little lost on how to proceed. The idea is to do figure out an estimate on costs based on the quantity of products being sold. I can do this in Excel, but the VB code escapes me.
So I'll show you in psuedo code what I want to do.
IF comboBoxA = 1 and comboBoxB = 1 then
value X
IF comboBoxA = 2 and comboBoxB = 1 then
value X
If comboBoxA > 3 and comboBoxB > 1 then
(comboxBoxA * costA) + (comboBoxB * costB) = Value X
I have another IF statement that will work off the calculations here. Haven't figured this one out yet, but I haven't gotten there yet in my form.
If Value X > Y Amount then
Offer product Z as a better idea
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Dec 18, 2009
I want to make multi level side strip with some data as shown in figure below:
The first column could be labels (names) read from an array or a variable and the second column could be a value to that label read from a variable or array. The value of the last column will be assinged to the label or in the first column. for example:
Column1 (level1) Column2 (Level2) Column3 (Level3)
Area1 => Value => 5
8
Importance => 9
[Code].....
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Aug 8, 2011
Background:I have a base class and several inherited derived classes. The derived classes don't always need to have the same properties. If any properties are shared among the derived classes, those properties would live at the base class level ('Contents', for example).Similarly, GoodDocument below has 'GoodThings' but would not want/need to have 'BadThings'.I want to treat instances of both 'GoodDocument' and 'BadDocument' as type 'Document'
public mustinherit class Document
public property Contents as string
public sub new()...
[code]....
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Oct 25, 2010
The first list box contains the project name. Based on whatever is selected in the Projects list box, the 2nd list box is generated with Custodian names associated with that project. I am having problems generating the 3rd list box. This holds the data sources associated with whatever is selected in the 2nd list box (Custodians)
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Aug 25, 2009
With the following code I only can add until second level node... If wan to add more level in child node?? I want to add child node to "UOM" node??
TreeView1.Nodes.Add("Maintenance", "Maintenance")
TreeView1.Nodes("Maintenance").Nodes.Add("2", "Item Group")
TreeView1.Nodes("Maintenance").Nodes.Add("3", "UOM")
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Feb 22, 2012
I've got this code
Public Class Form1
Dim m_listener As HttpListener = Nothing
Dim m_asyncCount As Integer = 0
[code].....
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Dec 10, 2009
I'm having trouble getting a numeric format out of a textbox.I can do this in the textbox validating event, but I need commas to be entered into the textbox as the user actually types the data, not after they leave the textbox.. the reason is that they are typing really large numbers and can easily lose track of 0's or the total number if there are no comma seperators.I tried to do this through the keydown event in the textbox, but that doesnt work the comma gets inserted but the cursor goes into the begining of the string so anything new i type goes ahead of the old stuff.is there really no formatting on the properties level of a textbox??? how can there be no datamask?
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Jul 29, 2010
In c# you can auto property a value with different level of access for the get and set . . . e.g.
public String myString
{
get;
[code].....
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Oct 28, 2009
I have a combo box on my application (working with VB.net) called CmbAttendantstatus. I have sent the dropdownstyle = dropdownlist at the Properties level of the combobox.
There are 200 field types e.g;
Current Attendant
Ever Attendant
Never Attendant etc
The issue is I can only select one from the list, fine, but I want to be able to type the first letter on the combobox and it takes me to the nearest field type rather than looking through the entire drop list. For example I want Never Attendant, I just need to type N and the drop list takes me to anything starting from N and if I add E for example any field starting with NE shows up for selection. Presently, when the dropdownlist is selected you are not allowed to type anything...
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Feb 28, 2011
I tried it and get an error but maybe I'm tring the wrong way. Can a usercontrol inherate an application defined class ie.. could you inheritance a classic rect class into a user control to add the hight and width properties to the control without having to do all the coding all over again? Currently I just declair a private instance of the class within the control and then encapsalate. It would be nice if I could just inherit all the functionality of my classes into controls designed to implament the classes.
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Dec 14, 2009
May i know how to change my below login code to support for multi access level login? So that i can differentiate between manager and normal employees login so that i can enable or disable certain features for different department? I have the below code that can serve as a basic login.
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
'login code can work
conn.Open()[code]......
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Sep 21, 2009
I have a UserControl that has a Property - Text. How can I allow multi-lines of text to be created in its Properties (as a TextBox)
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Oct 7, 2011
I am trying to implement a sub-class as a property of another class. Eg:
[Code]...
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Apr 1, 2012
I am creating an Excel add-in written in VB.NET. I would like to bind KeyDown and KeyUp events to the spreadsheet to record when the user presses and releases the arrow keys while navigating the spreadsheetIdeally, these events would be built into Excel alongside the native SheetActivate and SheetSelectionChange events, for example. Alas, they are not.
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Jan 6, 2010
In Visual Basic 2008, there's two different ways that I know of to accomplish the same thing:The Dim on the member level:
Dim counter1 as integer = 0
Dim counter2 as integer = 180
Public Sub SampleSub1()
[code].....
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Mar 18, 2011
I have created a simple program which uses a two tier structure of SQL Tables.At the top level, one record holds the date of the activities and linked to it using its primary key as a foreign key, three subordinate tables hold time stamped records.The issue I have been unable to solve is that before adding any of the lower level records for a given date, a newly added top level record must be saved to the database.Doing this manually is simple - but can I rely on my users to remember to do this before they start plugging in the lower level data?I thought not, so I am looking to save the top level automatically.I've failed miserably but I refuse to believe that it's not possible.
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Feb 12, 2011
I have multiple level of For Each and in each level, i have a Linq that is the 'In' criteria as in:
[Code]....
It will go inside each for (because the value is not nothing), however, it will only loop (next) in the very inner 'For Each t In tFor'. After it is finish inner loops, the outer Fors' or Next will not execute... even thought there are more than one values in that 'In'... like 'sFor' or 'fFor'. i've noticed while debuging, while break at the for (for example 'sFor', before stepping in), i get the error message:
"Enumeration yielded no results" when i expand the result for that variable and it will not step into it. but if i do not expand the result, it will step in. It seem that some how, once an element is accessed for that 'In' collection, it breaks (meaning does not loop for the rest of the elements) the next for that collection is this a bug or am i missing something in Linq? BTW: i believe it has something to do with the SqlDataReader in the Linq. I'm working with IAsyncResult.
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Oct 25, 2010
I need to know if a Type implements an interface. [Code] because the Interface IRule itself is assignable of IRule what raises a MissingMethodExcpetion if i try to create an instance:
ruleObj = CType(Activator.CreateInstance(typeAsm, True), Rule.IRule)
UPDATE2: IsAssignableFrom in combination with IsAbstract might be the best way to check if a given type implements an interface and is not the interface itself (what throws a MissingMethodException if you try to create an instance).
If GetType(Rule.IRule).IsAssignableFrom(typeAsm) AndAlso Not typeAsm.IsAbstract Then
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Mar 15, 2011
I have 2 classes that Implement 1 EventHandler. Its part of a fingerprint scanner API but I'm having some issue and I'm not sure if it is my fault in how i use the Implements.Is it ok to have 2 different classes Implement the same EventHandler? Each class then uses the events differently within the class but it almost seems like there is some overlap that is causing some issues. I know this is hard to explain without posting code but since i can pinpoint the problem, idk what to post. My main point is, can you have 2 different classes Implement the same Interface?
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Dec 6, 2010
Im trying to make a program that implements this but I cant seem to get past inserting the characters. Basicly to get a better idea on what im trying to do look here.Public Function permutation(ByRef charSet As String, ByVal minInt As Integer, ByVal maxInt As Integer)
[Code]...
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Dec 4, 2009
I've got a web user control (.ascx) which implements a couple of interfaces I wrote; namely IXMLBoundControl and ISectionOverridingControl.I've written a mini-CMS type application that dynamically loads controls onto the page based on information in a database. When I click a button on a web page (.aspx), I want to look at all the controls on that page, and determine if there is a control which implements the ISectionOverridingControl.
I've got my loop and I'm looping through the controls; that's fine. However I'm not sure what the best way is to determine whether or not the control implements the interface. What I'm doing at the moment (and works) is to try to cast each control into the ISectionOverridingControl and catching InvalidCastException: If I don't get the catch; I consider it's worked. If the exception is thrown then it doesn't implement the interface.
It's working, however, I consider this inefficient (relying on exceptions): surely there's a better way in VB.NET (I've seen an example in C# but it didn't convert to VB) to tell whether an instance of a class implements an interface or not?
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Sep 24, 2009
I am trying to check if a type implements the generic Icollection interface, since this is a base interface for any of my generic collections.the below code doesnt work
GetType(ICollection(Of)).IsAssignableFrom(
objValue.GetType().GetGenericTypeDefinition())
whats a good way of detecting if a type implements a generic interface?
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May 24, 2012
I have about 1000 webrequest created. Each link will navigate to a website and download a picture to place into a picturebox.
The person will then type in what animal is in the picture into a textbox. Then the user will then hit the submit button to send the name of the animal back to the site.
I am going to implement the use of a thread pool to handle the threading portion of those requests.
What is the best method to get my webrequest into the thread pool (listbox, txt file,etc?) and then how can I setup my button to coordniate with the site that is coming out of the pool to the picture box?
My first thought is to create everything on the fly. The picturebox, the textbox, and the submit button, the webrequest to the site for the picture and back again for the result. Something tells me that I will be taking the long way around to get same result.
My second thought is to have a slew of pictureboxes, textboxes, and buttons already on my screen and then when they come out of the pool and into a thread they would assigned a picturebox, textbox, and button if the others are not busy.
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Sep 1, 2009
I have an object parameter and I need to check if the object implements a specified interface in vb.net. How to test this?
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May 25, 2012
I have about 1000 webrequest created. Each link will navigate to a website and download a picture to place into a picturebox.The person will then type in what animal is in the picture into a textbox. Then the user will then hit the submit button to send the name of the animal back to the site.I am going to implement the use of a thread pool to handle the threading portion of those requests.My question is this:What is the best method to get my webrequest into the thread pool (listbox, txt file,etc?) and then how can I setup my button to coordniate with the site that is coming out of the pool to the picture box?My first thought is to create everything on the fly. The picturebox, the textbox, and the submit button, the webrequest to the site for the picture and back again for the result. Something tells me that I will be taking the long way around to get same result.
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