Get Notified When List Of Custom Type Property Changed?
Mar 2, 2011
I have a class and one of the properties is a list of a custom class. The caller gets the list and is adding instances of class to the list. How do I get notified that the list has been updated?
Private _list as List(of MyType)
Private _totalField1 as Integer
Public Property MyTypeList As List(Of MyType)
Get
Return _list
End Get
Set(ByVal value As List(Of MyType))
_list= value
_totalField1 = _list.Sum(Function(x) x.Field1)
End Set
End Property
What I'm trying to do is every time a MyType object is added to the list keep a running total of Field1, but adding to the list doesn't use the setter. How can I know when the list has been added or changed?
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 recently downloaded VB 2010 Express so i am quite new to the language, but i have worked with dark basic, which seems to b very similar.Anyway, my problem is that i cannot seem to correctly set out my array of a custom type/class. i am trying to create two arrays, one of available entities and another of selected entities of which the user selects the entities to be dealt with in irrelevant ways. i have creates a button (called test) which adds some entities to the available list and all the entities come back the same value but they shouldnt be as you'll c in the code. i have run the step into command a found that "available.item(#).Name = " will change all of the entity's names.As of current i am working with lists as the array kept asking for a 'new' statement but i couldnt figure out where to put it.[code]
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 have a datagridview that is bound to a list object of a custom type via a BindingSource. From everything I've read, I should be able to click the column headers and the rows sort, This doesn't happen for me. Sortmode is set to automatic and the column headers aren't set to be used for selection so it should work.
I know that I could sort progamatticly but that seems a little bit of a waste given that I should just be able to do it by default.
I have a listbox binded to a list of objects. For each list item I wanted to have a rectangle whose fill color is determined by a few properties of the binded object. So I did the following:
Made sure INotifyPropertyChanged was implemented on my object.Created a class to expose the properties I am interested in as attached properties.Binded the properties of the object to the attached properties of the rectangle Created a style that uses triggers to set the rectangle fill based on attached properties.
This works, but only the first time the property of the object changes. After that, the attached properties do not seem to be receiving notification when the data object's property changes. I have double checked and my data object is raising the INotifyPropertyChanged event.
I need to be able to tell if a property is of type List(of T)but am currently unable to. if i do
TypeOf (UpdateTo.GetType.GetProperty(node.Name)) Is System.Collections.Generic.List(Of Object)
I get the following error
TypeOf (UpdateTo.GetType.GetProperty(node.Name)) Is System.Collections.Generic.List(Of Object) Expression of type 'System.Reflection.PropertyInfo' can never be of type[code]......
I have been trying to solve a problem related to using RolesProviders in MVC.Basically I would like to an additional set of criteria to the roles table so that a user can switch roles based on what they are doing on the site.However as simple as it may sound its proving to be a nightmare. I cannot for love nor money come up with a solution. I have tried overloading the provider, creating extension methods (which never work with the Roles class) but finally I decided to simply create a reference to my own custom provider and just completely bypass the whole User, Roles class.Now I am getting a ridiculous error which states that I cannot cast MyProvider class to an instance of MyProvider class? All I am doing is calling the Roles.Provider method and casting its return value to my custom provider class (which inherits from RolesProvider). The asp.net forums are a waste of time since no one ever answers the questions and there are simply no examples of extending the Roles/Membership model without using SQL server.
I'm having trouble using DataBindings in a Windows Form / User Control. For example: Create a windows form, place a single text-box on it & place two buttons on it. The code behind the form is:
Imports System.ComponentModel Public Class Form1 Implements System.ComponentModel.INotifyPropertyChanged Public Event PropertyChanged(ByVal sender As Object, ByVal e As System.ComponentModel.PropertyChangedEventArgs) Implements System.ComponentModel.INotifyPropertyChanged.PropertyChanged [Code] .....
If you type something into the text box & press Button1, you'll get a message box with the text of the property in it. If, however, you press Button2 (which sets the property in code) and then press Button1 again, you'll see that while the property was indeed set in the code, the text box doesn't reflect the change.
Updated the code to provide the implementation of INotifyPropertyChanged. This now works as desired.
How can I make an event that is raised when a variable or property is changed (or can I just put the code I would put in an event in the Set section of a property?
I have an ASPX Custom Control which is supposed to load it's properties into an internal collection (defined with PersistenceMode.InnerProperty). Here's the ASPX
I have a problem with a property on a custom property of a class. Here is the actual code for the inherited form
Public Class Form : Inherits System.Windows.Forms.Form Private _Active_Application As Custom.Classes.Active_Application = New Custom.Classes.Active_Application <System.ComponentModel.EditorBrowsable(ComponentModel.EditorBrowsableState.Always)> _ Public Property Active_Application() As Custom.Active_Application
[code]....
but when i use a separate class to inherit the above class this property ('Active_Application', not Custom.Classes.Active_Applicaton) is disabled.
i created a custom control that accepts only datetime values. [url] but i'm having some issues with it when it is bound to a column and then i navigate through records. it seems to trigger a row-change to all navigated records even though i haven't manually change anything on these records.
this is affecting the last_update_date and last_updated_by fields of my tables. i need to only affect records that were manually changed. can anyone help me? also, any date field should be bound to the Value property of this control instead of Text. haven't figured out how to remove the Text from bindable properties yet.
This starts with an object being added to a collection with: CommonArgs.Add(ObjName, Me)
ObjName is a string, call it "Obj1". Me is an instance of a class inheriting from UserControl. Call it "Class1".
Now, to check the value assigned to Obj1, the vendor has the
Dim Obj As Object = CommonArgs(ObjName) Dim Info As System.Reflection.FieldInfo = Obj.GetType().GetField(ObjName, System.Reflection.BindingFlags.Public Or System.Reflection.BindingFlags.Instance Or System.Reflection.BindingFlags.IgnoreCase) Obj is the Class1 object added to CommonArgs.
When I run this in my test app, Info is Nothing-but when I run it in the vendor's app Info is an Enumerated type. Why?
I've found a little more info, but it's still a mystery to me-and so far it appears to be a mystery to everybody else, too.
First, I noticed that I didn't mention that the Collection is a Hashtable. I don't know if that would make a difference, but it is something I forgot to mention.
Second, there's a 'regular' variable named ObjName that contains the value being returned by Info. My understanding is that there's no connection between these, e.g. Dim X as Integer = 1 doesn't change the type or value of the object of CommonArgs("X"). But that's what appears to be happening.
I have the following property in a property grid in VB.Net 2010.
<Description("Rapid Entry Post Car Wash Settings CarWashOptionPushButtons"), _ Category("Post Car Wash")> _ Public Property CarWashOptionPushButtons() As String
[code]....
I need to make this property a list box that gets the values from a database table and populates the list box with the values from the table. I have tried numerous things to no avail.
I'm trying to write an application that will notify me when a webpage changes. I used a web browser form and it opens the main website fine. You have to click a submit button to get to the page that I need to track. After this page opens I copy the text I want to track into an input box and then I need to refresh the page every minute or so to see if the text changes.The problem I am having is I cannot get the page to refresh properly. I send the WebBrowser1.Refresh() command but my ap stops responding, but only sometimes. If the refresh works then I get a popup window where I need to send [enter] to get the page to
doing dropdown list selected index changed. I wan to select an item in dropdown list and display in textbox but I got more than 1 textboxes. Is the style sheet (.css) going to hard code by our own. how do I go about starting with it as I am a beginnner using visual studio.
I have a requirement where I need to have a "type safe" way of accessing property names, without actually instantiating an object to get to the property. To give an example, consider a method that takes as arguments a list of IMyObject and a string that represents a property name (a property that exists in IMyObject).
The methods implementation will take the list and access all the objects in the list using the property name passed... for some reason or another, we won't dwell on that!!
Now, I know that you can do this using an instantiated object, something like ...
Dim x as MyObject = nothing Dim prop As PropertyInfo = PropHelper.GetProperty(Of MyObject)(Function() x.MyProperty)
Where my helper method uses reflection to get the name of the property as a string - there are numerous examples of this flying around on the web!
But I don't want to have to create this pointless object, I just want to do something like MyObject.MyProperty! Reflection allows you to iterate through a types properties and methods without declaring an object of that type... but I want to access a specific property and retrieve the string version of its name without iteration and without declaring an object of that type!
The main point here is that although I am trying to get the property name as a string... this is done at run time... at compile time, I want this to be type safe so if someone changes the property name, the compilation will break.
I would like to specify a function to be called in my VB.Net 2005 WinForms project at midnight when the system date changes. Is this possible?I know I could do this by setting a timer by setting the interval to midnight minus the current time, then after the first tick, setting the interval to 24 hours. I was wondering if there was a cleaner, simpler way.
I have a VB.Net application that connects to a SQL Server database on my web host at GoDaddy. I'm wanting to use it for a chat program so that users can add messages to the database and then everyone else gets the new messages when it re-queries the database.
The only problem is that the only way to get the new messages is to re-query the database every # seconds.
Is there any way to have my program not re-query the database until an entry is added by another user?Would the SQL.SQLNotificationRequest be used for this?
it seems always at this time I cant figure out how to do something maybe it has something to do with lunchtime.
Im having trouble using a method that is defined by an outside company
This is a link to their integration guide:
[URL]
This is their documentation for the class Im trying to use
OrderQueryWebService Class
This class is for SID in particular and is made for use with the notification methods. This is for the Order Query Web Service specifically, allowing clients to return the status of transactions for their merchant, whenever they want to.
Methods / <summary> / Pass through the variables required and receive a list of Transaction objects showing transaction status
[Code].....
The MerchantCode, the MerchantUsername, the MerchantPassword are all good the List is a custom type called SetComHash.Transaction
Everytime I try adding a string to the list such as the transactionNumber and some other values it gives me a type error:
"Value of type string cannot be converted to 'SetcomHash.Transaction'
I'm looping all the properties in an object via reflection:
For Each p As PropertyInfo In values.[GetType]().GetProperties() If p.CanRead Then 'Do stuff End If Next
how to determine whether the property in question is a generic List(Of T)? If it is I need to loop the list itself.
I've experimented with GetType and TypeOf but have not managed to get anything working.
To clarify, I want to keep this generic. I do not want to specify the type of T, I need to loop the list items and call the ToString method on each item. T could be one of a number of different types (application specific reference types). Is it possible to do this without specifying types?
I am able to only add controls that are of type TextBox. My question to you is, can I create a List to hold more than one control type or do I have to create a list for each control type?
Moved from Microsoft Developer Network > Forums Home > Development Forums > Windows Debugging
[Code].....
MS has a patch for the OnListChanged event handler issue, even though it seems we have to pay to have access to it. This fix specifically addresses an error message when you press ESC to cancel adding a new row in .NET 2.0: [URL]
FIX: Error message when you try to press ESC to cancel adding a new row to a DataGridView control in the .NET Framework 2.0: "An unhandled exception of type 'System.InvalidOperationException' occurred in System.Windows.Forms.dll"
The intention is to convert an IList of custom objects to a string equivalent comprising each element in the Ilist. Unfortunately I can't seem to find a way to get the underlying data of the custom object, and of course as in the above example, using object simply gives me a string of types definitions, rather than access to the underlying data.
I know how to handle a single objects property changed event very easily. I want to handle a objects property changed event that is part of another object.
Given Object:
[ObjectY = Y] + Public WithEvents X As ObjectX
I would like to do something like:
Private Sub XPropertyChanged() Handles Y.X.PropertyChanged
Right now I need to create a object that equals the object inside that object and then handle this variable pointers property changed, but that is just annoying.
