Dynamically Referencing Class Property With A Variable?
Feb 4, 2009
So Im iterating through the properties of a class. For each property Im iterating through a datatable until I find a column name with the same name as the property.
No worries so far, here's the isse: Once I've found a match I want to set the class's property to the value in the datatable but I'm having difficulty referencing the property as it has to be done through a variable.
Code:
Dim per As New Person
Dim t As Type = per.GetType
For Each p As PropertyInfo In t.GetProperties
[Code].....
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Dec 24, 2011
How do you reference a variable in another Class?
Public Class Form1
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
TextBox1.Text = "Class1_Text" ' Would like to replace w/correct code
End Sub
End Class
Public Class Class1
Public Class1_Text As String = "Class1 Text"
End Class
I can reference the Form1 data in Class1 but not vice-verse.
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May 6, 2010
I have a collection class, say ITEMS, that inherits a Dictionary (of String, SINGLEITEM). From the SINGLEITEM class, I would like to reference a property in the parent ITEMS class, what is the best way to do this? For example, say the ITEMS class has an IsDirty property and I would like to set that if ANY of the contained SINGLEITEM objects is modified, what's the best way to go about doing this?
I know I could add a reference to the collection class in each SINGLEITEM class (since I override the ADD method, I could make this assignment), but this seems like overkill.
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Sep 29, 2011
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
[code]....
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Nov 14, 2009
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]
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Nov 4, 2010
I want to set a variable in a class. But I want to dynamically choose which variable to set.
[Code]...
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Dec 30, 2009
When referencing class properties from a function within the class do you use the value from the actual property or the private variable value?
public class
private m_Foo as double
public property Foo() as double
[Code].....
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Mar 17, 2009
I would like to dynamically create an object (in my case a thread) and then be able reference that object. Simplistically put, I would like to read from a text file and then process each item using a thread (so that I don't have to wait for each item before starting the next). The problem is that I cannot think of a way to create a new thread dynamically ie. thread name so that I can then wait for all created threads before doing something else.
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Apr 26, 2011
I dynamically (by programming text, not drawing in GUI) created a matrix of 10x10 buttons named 'Button1' till 'Button100'. In a formula I calculate a number, say '87'. If I next want to reference 'Button87' and change e.g. the background clolor and text properties, how would I do that? I am creating a PocketPC game using VB2005.
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Jun 26, 2011
MyProperty is just a property defined in another class. However when I try to reference that property as shown below I get an 'Identifier expected' error
This works:
TDTL.DataTopLevel(FileNumber).DataSet(FileDataSetNumber).MyProperty = TempVar
This does not work:
dim poo as string= "MyProperty"
TDTL.TireDataTopLevel(FileNumber).TireDataSet(FileDataSetNumber).(poo) = TempVar
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Oct 29, 2010
Consider the following case:
Public Interface IHasDateUpdated
Property DateUpdated As DateTime
End Interface
Public Class MyClass
[code]....
Now, assuming I was referencing an instance of MyClass as an IHasDateUpdated; how would I determine the actual name of the property that implements the interface property via reflection?For example:
Dim x As IHasDateUpdated = New MyClass()
' How do I derive "MyDateUpdated" from "x" using x.DateUpdated?
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Feb 1, 2012
I am converting an application from vb.net 2003 to 2005. I got the following warning and need help how to resolve it. withEvents variable 'PreviousPage' conflicts with property 'PreviousPage' in the base class 'Page' and should be declared 'Shadows'
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Feb 15, 2012
I have a question about assigning variables values based on values stored inside an sql database. I have the connection part down, but here is my basic set-up. I have a table with the values {username, password, isAdmin}, where username and password are strings and "isAdmin" is a bit variable. I am able to read in the username and password entered by the user and match it to the database fine, however I would like to also read in the "isAdmin" and set it to a local Boolean variable that will then direct the user to the proper form.
[Code]...
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Feb 20, 2009
how to create a class yet, and I think I need to learn how.I am wanting to shorten my code in a form, thinking of creating several classes to do so.Lets use a Listview as a reference if you dont mind.Say there is a listview, you have a numeral amount of if statments to fill by. Is there a way to create a class(is this the way to go) so that you can open the class to modify that specific block of code? Example of questionYou have multiple items you need to add for each if statement. Animal as a group Dog as an item 14 years as a sub item Cat as an item 11 years as a sub itemIs this the way to go, if so how do you create a class and call it from a form?Davids Learning
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Nov 18, 2011
I am building application that will be hosted as a web service. This app takes an employeeID and returns an employee object that contains lots of info regarding the employee. (name, status, full-time/part-time, etc)I want the two existing apps we have (and more to come) to be able to call a method that the web service will have and return the employee object. (also at time this web service that returns the object may have new fields added to it - Pay rate, etc)How would I go about creating a new object from this web service reference in the existing applications.Would I decalre it like Dim Employee as new emp_webservice.employee? And then be able to use this object within the app? Or would the better practice be to also included the same class files? It seems like this would not be the way to go, since if I make a change to that class I then have to make it in all places.
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Oct 8, 2010
I have several sets of similar objects (labels, progress bars) on a form in Visual Basic 2010 on Windows. In my code, I have collections that contain data, which needs to be pushed into the value/text property of each.
I would like to get a solution similar to PHP in that I can assign values somewhat like:
For ID as Integer from 0 to count(collectionExample)
lblExample{ID}.Text=collectionExample(variableID)
...and as such to loop through so each of the different lblExample's were updated to their corresponding value.
The issue I have come to is that I cannot seem to reference an object on the form using a variable. I have also tried using something like
CallByName("lblExample" + variableID, "Text", CallType.Set, exampleCollection(variableID))... however I still can't combine the string and variable to reference the object.
Any solutions on referring to objects in VB2010 by combining a string prefix and a variable string identifier, similar to PHP's $variable{$variable} approach?
Edit: Windows Platform
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Aug 23, 2010
How can I implement a tree structure (Octree) in Visual Basic.
that is to declare a class containing array of objects of same class type - like
Class Node
{
dim ....
[Code].....
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Feb 25, 2010
when using variables in object names.I have a Public class which is called "Tank".In that class, there is a public property called "direction" of an integer type.I keep getting the error:
"Tank is a type and cannot be used as an expression"What I'm doing wrong here ?
Public Class mainroutines()
Create Instances of tank
Private Tank1 As New Tank()[code]....
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Jun 4, 2011
I have created an SNMP class. And then I want to test this class, so I create a program which imports this class ...
Imports SNMPClass
Module Module1
End Module
Public Class SimpleSNMP
Public Sub Main(ByVal argv As String())
[Code] .....
I got an error in this line
Dim conn As New SNMP()
Which says "SNMPClass.SNMP is not accessible in this context because it is friend"..
I am using Visual Studio 2008
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Feb 15, 2012
I'm working on a legacy vb.net application that does most of its work using inline code ( Within that script I need to access functions from a third party .net dll. The dll(s) themself are stored in the GAC. Before I started the page looked something like the following
[Code]...
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Jun 8, 2012
Referencing an object (class) within a thread fails
I have an object ("a vb class") that needs to run on a separate thread and communicate with the U/I.
Even using sample code, I cannot get the object to run within a thread. I demonstrate this problem with two examples. The first calls a function within the form and it works perfectly. The second creates an object and performs the same calls, but fails.
example #1 [working] (Called within a form)
Private Delegate Sub FuctionToBeRunInThreadDelegate
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
[Code]....
SUMMARY: When the thread creates the object, it appears that the object is not actually running inside of a thread or else form.InvokeRequired would be true. I have other more complex examples where this is strongly verified and evidenced, but I provided these two as a very simple demonstration of my problem.How can I have a thread "own" a series of individual objects so that the objects are run asynchronously and can independently report back to the U/I?
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Aug 12, 2011
I have class file class1.vb with 3 classes class1 , class2, class3. a class file class10.vb with class10 class11 class13
I declared class 1 public and declared a public shared new instance of class11 in class1 at the top
All classes in class1.vb can use this shared instance, but a form4.vb doesnt see the shared class1.(new instance of class11)
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Oct 5, 2010
class
eg: dim classobj = xyz("CLASS_NAME") ' where classname is a valid class name
and dynamically raising a known method of that class on that newly created object or class reference.
[code].....
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May 31, 2012
Now I have the need to get a current value from a bindingsource in a property of a user control.In a previous thread I had tracked down the "Object variable or With block variable not set" to the return in the Get block of a property. At the time I was only using the Set so I just commented out the offending code until I needed it.
[Code]...
The error does not occur during a system compile, only upon saving the container object of the user control. As I said the Set works correctly, only the Get causes the error.I would like to know what I am missing/misunderstanding and am open to other suggestions of handling retrieving the current value of a bindingsource in a user control.
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Aug 4, 2009
I want to assign an object property by referencing the property dynamically, with a variable name
i.e.
dim propName as string
staticObjectName.propName = 'whatever
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Jun 1, 2012
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.
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Aug 18, 2010
Say I have a Framework 4.0 project that is referencing a class library targeting 3.5. The project will simply not build. It won't give me any valid error message it will just act as though the reference does not exist.
Projects that were working like this in Visual Studio 2008 are no longer working in 2010. Took me forever to figure out what there error is. If I remove the project reference and add it back the intellisense lights up and you can tell a variable referenced in the class library is found. But as soon as you build the project everything is lost. My using statements get underlined, references to the variable all turn grey and project fails to build saying the class cannot be found. Once I make the class library 4.0 as well everything builds. I get the same issue between 4.0 client profile and 4.0 as well.
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Aug 13, 2009
I have the following code:
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'?
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Apr 7, 2011
Supose a base class
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)?
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May 14, 2012
is there a way to dynamically assign value to a propertyso I have a class
Public Class RulesInfoVO
_RULES_ID As Integer
Private _RULE_PRIORITY As Integer
[code].....
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