How To Create A Connection Between A Control And A Property In A Class
Sep 20, 2010
Is there a (simple) way to connect a textbox, label etc. to a property in a class?I have a project with a complex series of dialogs to enter data into a list of a costum class describing an experiment with many parameters that are stored as properties (both simple variables such as strings and integers, but also more complex ones).I need both to be able to update the list of my experiment class, but also to go the other way to populate the dialogs from the class.It can of course be done outside the class and the dialogs in separate subroutines. This however, quicly becomes unmanagable and hard to maintain as the dialogs and experiment class is expanded with new elements.If there was a simple way to connect say a textbox or label in a dialog with the appropriate property holding the information it would make it much easier.
Is it possible to create a user control with a list of custom class type property? If it is, how can I? The issue is that, in designer mode the property is not displayed in property window. I can add the list on markup but when i switch to the designer mode it gives an error which is 'The user control does not have a public property named BookList'.
I want to create a class in vb.net that make the connection to database.Also I need the way to use this class inside forms. I need a code example of both the class and the form call
Interface makes sure a class does have a Method / Property, However is there a way to create an unInterface, making sure that the class does not have a method / property or is there a way to implement something that will unimplement every other implements except for itself?
what i want to do: i've got a class that serves as a storage for information only, so i decided to give it a blank interface IBank, the other classes that share this feature will implement this interface. they should not implement any other interface the use is that when i seek out the interface of a class and realise that its IBank i know that its just a class for info storage.
If we say blue is the default colour of the Backcolor property I understand it as if you don't specify a colour for Backcolor blue will be its colour. But I could not make sense of default property of a class in the context of building a custom user control. After calling an instance of a class we have to either call one of its members or assign an other object for it. Therefore why should there be a default property?
When inheriting class or control e.g. ListView, TreeView, etc..., what is the best way to distinguish between built-in methods/property/events and mine?
Currently, i start my methods/property/events with "aa" in order to make them at the top of auto complete list.
I need some help to understand my options to get this working. I try to update a textbox control by a property-changed event from a class variable. I've digged around for a day and have a vague understanding that this can be solved in three ways:
1. Using some "if InvokeRequired", "Invoke" code in the handler method 2. By programming a special delegate class for this variable 3. By using a databinding directly linking the control (textbox) to the class event
Now.. Are these options correct? And would it be possible to get some help to show these three solutions in actual code (relevant to mine)? I can't seem to manage to sort all the information to a working code. Also, what are the pros and cons of the different solutions?
As my code stands now, it's obviously none of the above, as it gives a cross-thread error, as indicated.
I want to create a custom control (let say textbox), after build, when I place that custom control on a form, all the properties for the default textbox are available.
1- How to Hide them and only show the wanted property and method?
2- Is there a Wizard or custom tool for creating custom control or I had to do every thing by coding?
I've created a custom user control that has several properties. One specifies which database I want the control to access. I want to be able to present the user of the control a drop down from which he can select which database the control will interact with. How do I get the dropdown to work? I can get default values, but have yet to figure out how to get the selectable list.
I'm trying to use it in writing VB.NET Windows Form code.So I'm thinking, instead of using a VB.NET module, or having code embedded in the forms, I should create my own "Control" Class, to handle all operations and "application" level variables.Is this the right approach?Ex:
Private Sub frmLogin_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load goControl = New MyControlClass() goControl.sUserID = txtUser.text[code]....
I need to create a class to control a texbox.Basically a keypress event but in a class.
I have a textbox on my form.This is a textbox for the postcode.The postcode is supposed be something along the lines of AA 1234.Not sure if its possible, but i want this to be checked on lostfocus.
I honestly got no idea how to get it to work in a class, or to link it to the textbox.
is it possible to create application for my mobile phone Sony Ericsson to remote control my program using Bluetooth connection which have simple functions?I have came across one program that is able to do that which is floAt's Mobile Agent. It can control from media player, powerpoint slides and even mouse cursor movement.
I have a very simple class that holds a few public properties - ID, Text, Colour, etc. and a Boolean called 'SelectedItem'. Just like the Checked property on RadioButtons, only one item can have its SelectedItem property set to True within a particular group. Note: there will be several separate groups (lists), each allowed to have only one item with SelectedItem = True.
My first thought was that I would probably just have to handle everything outside of the class, setting SelectedItem to False for every other item in a particular list when another item was selected. But that seems rather inelegant to me. So I've been trying to think of how this might be done within the class. For example: could I perhaps have a private string property called say "GroupName" - set in the New sub when adding a new instance of the class - and then use a private shared method to set every item's SelectedItem property to False, provided the item has the same GroupName as the newly selected item? I would have a go at doing this but I have no idea how to enumerate every instance of a class from within that class, or whether that's even possible. Is it? Or is there another (better) way to achieve my goal? Here is a cut-down version of what I've got so far:
Public Class ResourceItem Public ID As Integer Public Text As String[code]....
As can be seen: instead of instantiating a new ResourceItem and passing that as an argument to the manager's Add procedure, I'm simply passing the details of the new item and the procedure is creating the item from those. I don't know whether this is a good or bad idea - please advise - but I've done it because I couldn't figure out how to make the SelectedItem property only writeable by the manager, so I wanted to avoid having directly accessible objects that could have their SelectedItem property set to True without it deselecting all the other items in the same group. Of course that still leaves the possibility of setting a variable to one of the manager's list items and setting it from there, so I would still like to know how I could prevent that, if possible.
UPDATE: I didn't use the code above in the end, deciding instead to go with Cyborgx37's solution - which seems to work perfectly well for me despite the warnings about best practice. I also realised I would need to use the same class in another scenario where multiple items could be selected, so it was easy to add a Boolean property to the manager to enable that.
Public Class MyColorsClass 'Constructors Public Sub New() 'Empty Constructor
[code]....
However, if the empty constructor was called to instatiate this class then the colortype is not yet set. Therefore, if one accesses the 'IsColorCool' property it will always return 'False'. Now for the sake of this example, I must keep the empty constructor as part of the class.Now I could add some code in the 'IsPropertyCool' to check and see if a ColorType has been defined, and throw an exception if it has not been set, but I don't really want to do that.I also could always move the logic OUT of the property and into a method on the class called 'DefineIfColorIsCool' or something, and make the owness on the caller to make sure the method was called if they want to use the property 'IsColorCool'?
Public Class airplane Private var_num_seats As Integer Private var_num_engines As Integer
[code]....
Obviously, I don't wish that the class Glider has the method "start_engines" neither the property "num_engines". Otherwise, other child classes may have. How can I supress these property and method in child class, not just ignoring (if I can)?
I have procedure (Import) that calls a for a new instance of frmImportData. I also have a class name clsBatch that has a data table property called prpParametersTable.For some reason, I get an error (indicated below with ERROR>>>) when trying to assign prpParameterTable to cv_dtImport2. The error states "Object reference not set to an instance of an object.". Why does this error not happen when I assign dtBP to cv_dtImport1? Both cv_dtImport1 and cv_dtImport2 are equal to Nothing and in my Import procedure dtBP = prpParametersTable.
Public Sub Import(ByVal clsB As clsBatch) Try Me.cv_clsB = clsB
I have three class files, accounts.vb and transactions.vb in addition to my form.vb. I am unable to retrieve a member variable from on class from inside the other. When the combobox index changes, the program loads the correct account (checking or saving) from two different sequential files. I don't think I have the calcBalance procedure in the correct class file. And that is what I am having trouble with. Accessing it to display it. [Code]
This is a bit of a continuation from a previous post for which AtmaWeapon was very informative.
Problem: A parent class has a sub class with various properties. A property of the parent class is a List(of T) with T = the sub class The issue is how to store data in the sub class of the instantiated parent
Some example code (hopefully formatted correctly):
Code: '=========== Class Definitions ============= Public Class courseClass Public Class timeTableClass
I'm looking for a tutorial on how to Adding a list(of Class) or Collection as another Class's Property.What I am after is something like the Columns Collection for the DatagridView control.I would like to add Items in the graphics screen. Where the item list is displayed in the left panel and the selected Item properties are displayed in the right panel.
I have a class that has the following property that is generated by the methods in the constructor.
Public Class clsLoadTables Private _ds As New DataSet Public Property ds() As DataSet Get
[CODE]........................
My problem is that I do not want to inherit this class, but I have other classes that need to access the ds DataSet property. If at all possible I would like to not use inheritance and not load my datatable more than once in the program.
Here is my failed attempt to access the property inside another class that is not inheriting clsLoadTables:
[CODE].........................
How I can access this dataset that I want to load only once in the program from many classes without using class inheritance or a global module?
I know that an interface can contain another interface within it.But;can a class contain another class within it?Can an interface contain another interface within it?
I Want to develop a software like Yed.i just don know where to start.how we can create a workspace where i can drag and drop icons and create connection etc etc.
Im getting "connection property has not been properly initialized" error message on command2.ExecuteNonQuery().
I Have an SQL query which displays its result in a grid view (one result only) I'm attempting to get this result to update the database with this particular result from the SQL query
When i am try to execute following code it gives "ExecuteNonQuery: Connection property has not been initialized" error,
Try Dim cmd As New OleDbCommand Mycn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=E:\MILIND\Structure\Reports_DB.mdb;") Mycn.Open()
