I have created a new usercontrol. My usercontrol contains several other controls like labels, buttons and so on ...When I set the Font property of the usercontrol I want that font property value to propagate down to the child controls.
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I freely admit that I tend to avoid using API calls as much as possible I wish to use this API call
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In the form design I set up a TableLayoutPanel, 20x20 cells and in cell (1,1) a PictureBox (called Target) containing the image of a small target. The properties box for Target shows some very promising properties, Column and Row - and if you overwrite the values in the properties box, the PictureBox obligingly shifts to the corresponding cell position in th design. However in VB it is not possible to refer to Me.Target.Row or .Column - neither appears during coding in the menu of properties, and deliberately coding either of them produces an error like
Error 1 'row' is not a member of 'System.Windows.Forms.PictureBox'.
1. Why does the properties box show properties that cannot be altered programmatically?
2. How can my program move Target around in the TableLayoutPanel?
In VB.NET there is a keyword 'shadows'. Let's say I have a base class called 'Jedi' and a derived class called 'Yoda' which inherits from 'Jedi'. If I declare a method in 'Jedi' called 'ForcePush' and shadow that out in 'Yoda' then when calling the method on an instance of the 'Yoda' class, it will ignore the base class implementation and use the derived class' implementation. However if I have an instance of 'Yoda' that was declared originally as of type 'Jedi', i.e. Dim j as Jedi = new Yoda(), and called the 'ForcePush' method on the instance, it will use the Jedi implementation.
Now let's say I have an event that is called 'UsingForce' which is raised when the 'ForcePush' method is called, and I shadow the event out in the derived class (this is because 'Yoda' has an interface 'IForcePowers' that declares this event) and each class raises it's respective event.
If I have an instance of 'Yoda' that is declared as type 'Jedi' (like above) and I put an event handler on the 'UsingForce' event of 'Jedi', and then the 'ForcePush' method is called in the 'Yoda' class, will this event handler be reached?
I have a two windows forms classes, a base class and a derived class. The base class has an event handler which handles ValueChanged on some component. I have also written a different event handler for the same event on the derived class.
When I create an instance of the derived class and fire the event, I find that both event handlers run (the base class one and then the derived class one). But I want only the handler in the derived class to run.
Edit: Here is what the code looks like (can't post the actual code):
Public Class BaseForm
Inherits System.Windows.Forms.UserControl
(Windows Form Designer Generated Code)
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It works, but doesn't save what I've changed it to. In the designer everything works fine. I can change the text and have it update on my button control. BUT once I run or rebuild in any way, the text property changes back to it's default value, in my case "Button Control"These are what I've tried, and I've tried all with both Shadows and Overrides - both with identical outcomes. So I've just indicated that with Shadows/Overrides.
vbnet
<DefaultValue("Button Control"), Browsable(True)> _ Public Shadows/Overrides Property Text As String Get Return MyBase.Text End Get Set(ByVal value As String) MyBase.Text = value Me.Invalidate() End Set End Property Private _Text As String = "Button Control" <DefaultValue("Button
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shadowing and delegate method?
View 8 RepliesI have a couple of small classes to represent parts in a search filter. If the searched value equals NonValue the filter is supposed to do nothing. This is defined in a Base Class:
Private Class BaseFilter
Protected NonValue As Object
Protected sQueryStringBase As String = "AND {0} {1} {2} "[code]......
When I then create a StringFilter and check for allowed value:
Dim stf As New StringFilter()
stf.CheckNonValue(MyString)
I get a NullReferenceException (NonValue = Nothing) , when I expected the NonValue object to be String.Empty. Is this a bug in my code, or am I trying to achieve polymorphism in a wrong way?
I'm in a project where it's pretty much my first time doing all the architecture myself,and I'm running into a frustrating situation. My architecture for forms seems to be correct from a heuristic perspective, but I don't think its implementation is correct.
My architecture is thus:
Base Class: OrderForm
Child Classes: PurchaseOrder, Invoice, Credit
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Shadows vs. Overrides in VB.Net.What's the difference between shadowing a function in a base class in a subclass and overriding the same function? There is performance issues involved too?I know how to shadow and how to override in VB.net. My question is about when and why should I shadow a function instead override it and vice-versa.
View 2 RepliesI have been given an old dll and the assignment of accessing it through C# .NET 3.5. I believe the dll was originally built with VB6, but am not positive. There is no documentation or source for the dll aside from an example for how to use the it in VB6. I have been able to succesfully access it through VB.NET 3.5. Example code for accessing looks like this:
myLib = CreateObject("MyLib.api")
myConnection = myLib.CreateObject("NameOfConnectionObject")
myConnection.do_something("abc")
There are several different objects that are created from the library and all of those objects have different methods. I tried using different dll reading tools, but all the export methods show up as garbage. I also tried importing the dll in visual studio, but I get an error stating the dll is not accessible and/or not a COM object or assembly. So, I only know about the methods from the old documentation which is sparse. how to access in C# and/or find out more about this mystery dll?
i cant understand what constants are.
View 3 RepliesPrivate Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click
Dim d As Integer
Dim price(20) As Double ' Adjusted close price
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What is the for ... next loops in the second subroutine doing? What is the sim() array meaning?
I have a modem that I've been trying to communicate with only to discover this....went to the modem properties and queried the modem.....
AT+FCLASS = 0,1,8
AT#CLASS = ? COMMAND NOT SUPPORTED
(And I had been trying to use AT#CLASS = 8 all day).So, what does this mean?That the modem is automatically in voice mode (or will automatically choose it's own mode) and forcing it isn't necessary?Still no luck with the connection response messages either -- RING, etc.All I can do is make a call and the called number will appear in a textbox.
I am getting a build error. If I try to build again after getting this error, it will build just fine.
View 9 Replies[code] I cannot seem to understand why left & lan isn't working in the vb 2008 edition
View 2 Replieshow to understand a msakeditbox in null?
View 4 RepliesI've been trying to understand classes and objects. Yes, I'm thick headed and slow, but I made the decision to go to .Net and I am determined to improve my coding skills to be more efficient. I have spoken to Atma several times on the topic and read most of his posts concerning classes and objects, but still came away a little baffled (He's really advanced for me yet). I needed a simplistic analogy for a reference point to begin understanding. I was reading about OOP written by MikeJ in the following thread/post ...[URL] and it all started to become clear in this statement , but I would like some reassurance that I'm getting it ..."A car IS-A vehicle, while a dog HAS-A tail. The car would be an object declared as type Vehicle, while the dog would have a member that IS-A tail. However, Fido IS-A dog. The dog class is the base template for all dog objects, so when we declare Fido as a dog, Fido is an object. Since Fido IS-A dog, Fido HAS-A tail."
From this I have taken the following understanding...
Vehicle ... ' Class
Car ....... ' Object
Truck ... ' Object
Van ....... ' Object
And from that can I infer that this is true?
Dog ....... ' Class
Fido ... ' Object
Tail .. ' Member of Fido
So to apply this to a program I wrote recently that tracks Generator service...
Generator ' Would be the class
Brand X ' Would be an object
Spark Plug ' Would be a member
Gas Tank ' Would be a member
Brand Y ' Would be an object
Brand Z ' Would be an object
This statement also helped ...
""Class" and "object" are sometimes used interchangeably. However, classes describe the structure of objects, while objects are instances of classes. Each instance is an exact copy of its base class. Because an object is an "instance" of a class, the act of creating an object is called instantiation. To describe it better, a class is a blueprint, and an object is a building based on that blueprint". I can understand this (I think) and it refers to a basic template such as ..."Generator" (my class or blueprint or template) Generators have an engine, powerplant, fuel tank, etc. These are basic requirements to be a generator. (Template or Blueprint) They can differ by Brand of engine, Size of powerplant, and type of fuel used. (Based on template or blueprint) Do I have it down now? MikeJ also made this statement ..."you can't access certain types of class members from outside of the class itself." From this I assume you would need to assign a Global variable the value of the class member if you needed to use it outside of the class?
I'm just getting back into VB and was never a pro. The last environment I was in, briefly, was VB6 but spent a good amount of time coding in early VB's back to QB.I'm trying to read RSS feeds and found a nice demo reader but now I want to understand the code I'm seeing:[code]
1. Why does the demo create a new XML to read through an existing XML or is this all in memory as I can't find an actually file? Is this even needed as what I want to do is read the RSS feed, grab some info from it (Source, Title of each story, Date stamp, author and the story text) and then process that in various ways (not actually view it... I want to e-mail specific stories directly to me that fit my search criteria). Or is this just opening the XML out on the web? That would explain why sending it "test" gives me an error saying it can't find "test" in the bin folder as without an HTTP address it goes local.
2. doc.load... what check can I perform here to be certain that the data entered by the user is actually a valid feed? It should, for example, have a first line header that is reliable but is that the best method?
3. Where or how are the elements stored that I can then refer back to pull the data out I want?
4. I don't understand how this part works: navigator.Select("/rss/channel/item/title") Can someone shed some lite on the 4 pieces at the end?
5. I'm assuming the clean-up isn't really needed for e-mail but I didn't remove it as it doesn't seem to harm anything.
I have Visual Basic 2010 and also bought a book to study and practice problems. I know how to add controls and assign properties but get confused with the coding part.understand this somewhat?
Here is one problem I am working on-
Write a program to make change for an amount of money from 0-99 cents input by the user. the output of the program should show the number of coins from each denomination used to make change.
Now I know what controls i need on the windows form but I am sorta lost on the coding to make this program work.
At the following cmd.ExecuteNonQuery() line, I get the following error message: [code] I have followed the example at page [code] as closely as possible, but it does not work.Additionally, I am not sure of the syntax for the length (64) that I have for the BigInt or if it should even have a length.All of the examples that I have found in MSDN uses only parameters with character rather than numberic type. [code]
View 6 Replies"write sub prototype for a procedure whcih is named my data and has first parameter as a string which can be changed and second parameter of an integer which cannot be change"
View 3 RepliesAre you familiar with prefix and postfix? I just wonder how to solve it especially if the expression is too long.
View 17 RepliesI want to make an application that will remind me to give a break once in 45-50 minutes. But I want it to determine if I am playing a game or not at the time that I have to give break. In short, if any application is in fullscreen mode (or maybe using graphic card) I want to know. Is there anything about that in .NET?
View 12 RepliesCan someone explain to me what this is doing.
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My questions isn't really about a programming language but, since I did not find a general programming forum, I chose this one as I know VB.Net. There's this game, that you might already know, which is called Star Wars Galaxies (And is ending soon actually .. ). For each account and character, the game automatically saves chat logs in a .cht file. A player can have multiple chat channels that have different chat filters (group chat, public chat, etc) and they are all saved in this file. I'm thinking they are probably separated by some kind of a "flag" for the game to be able to detect them.
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I am referring to this document on MSDN. I understand what ".BeginInvoke" does, however looking at the example code on the document.[code]The delegate myDelegate (and the DelegateMethod) accepts a control and a string, but, at the .BeginInvoke, a Label control is passed and an array.[code]Shouldn't a string be passed instead of the array? Am I missing something?
View 2 Repliesif a call to For Each starts by calling the Enumerator's MoveNext, then Current, then MoveNext, then Current, and so on until MoveNext returns a False then it exits, am i right to say that the Reset is never called?initially i thought that Reset would be called when MoveNext returns False, i tried this (a msgbox would come if it was ever called but i got no msgbox at all)
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if that's the case, what exactly is the use of the reset in an ienumerator, and is it ok to leave it empty, as such
I'm trying to understand ComboBox and the use of columns (or equivalent) in .NET For instance, I have a bound form with a combo box and a table that i want to feed it. In the table I have EmployeeID, LastName, FirstName. I want the "Bound Column" to be the EmployeeID, but the combo box to display the last and first name of the employee. This was very easily obtainable in VBA but is giving me some grief in VB.NET. I've played around with the datamember and valuemember properties of the combobox but have not had any luck.
View 2 RepliesI'm trying to understand the concept of Raise Events and threading, From this tutorial i've just read in the author example he wrote that you need to use an event when calling sub when using threading, but he didnt elaborate enough in this subject, why can't I just call the function/sub as i always do?
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