PropertyChanged Event Cause Get/Set For All Persisted Properties
Aug 8, 2009
I have constructed a graphical user control using VS2008 and I am testing it in a solution that includes the control project and a sample form with the control and some configurable settings. In the test application I have persisted a few of the control property values in user settings.
I am using a standard template for all the property Sets in the control:
Set(ByVal Value As Integer)
If my[-propertyname-] <> Value Then
my[-propertyname-] = Value
[Code]....
Whenever the user changes a property in the control using a procedure in the test app, the PropertyChanged event is causing a GET (settings value) and SET (control property) for every property of the control that has been persisted by the test app, including the property for which the user just made the change.
I can understand that the settings code is listening for PropertyChanged events in order to keep the settings values updated (and I can trace the Get (control property) and Set (settings value) that is executed immediately after the property changes), but why should it also hook in a complete re-initialisation of all control properties every time the user changes one control property?
I have a class with two descendent classes (child, grandchild):[code]When a property changes in the Measurement class I raise a OnCrucibleOxidizedMassChanged event:[code]However, the OnChanged sub gets called twice, even though I only assign a value to CrucibleOxidizedMass once.
These classes are entities in a LINQ to SQL file. In the Measurement class, I raise the PropertyChanged event when the CrucibleOxidizedMass property changes:
Private Sub OnCrucibleOxidizedMassChanged() RaiseEvent PropertyChanged(Me, New ComponentModel.PropertyChangedEventArgs("CrucibleOxidizedMass")) End Sub
In the BaseSample class, I want to respond to the CrucibleOxidizedMass PropertyChanged event in any of the descendent Measurment instances. How would I do this?
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 have a VB.Net web site and on my sign up page I am storing the ViewState in Session. I am using the following code to achieve this.[code].....
This has been working fine for months, then I started seeing the occasional 'System.NullReferenceException: Object reference not set to an instance of an object.'. The exception is raised when I try to get the value of the Text Property from the SelectedItem of a DropDownList, the problem being the DropDownList does not contain items after the page has posted back.The problem is only present when using IE (7 or 8 according to my logs, but I have only tested with 8), but not when using FireFox 3.5.Reverting to using the normal ViewState persistence mechanism caused the page to work in IE again.There are no ViewState related exceptions logged, it is like the page just 'thinks' it has no stored ViewState.
once a class has been persisted on an hard disk with a strem is it neccessary to load the full class to deal with one part of it or is it possible to get just the part of the class i am interested in?
I was just wondering what is the Quickest way to set up custom settings, every software has settings that are created and saved, Example a Hotel Software has rooms, roomtypes etc that are used in combination with other things, an Accounting software has Account type, Employee Software will have Full time,Parttime, or anything else, An Employee time Clock would have departments, Tax Brackets.
I have a textbox and a button. Initially the button should be disabled, but when I change the value in the textbox I want to enable the button. I tried to write a trigger.
Dim handler As PropertyChangedEventHandler = Me.PropertyChanged
but it does not work in vb... I get this error:
Error1'Public Event PropertyChanged(sender As Object, e As System.ComponentModel.PropertyChangedEventArgs)' is an event, and cannot be called directly. Use a 'RaiseEvent' statement to raise an event.
I have a situation where I serialized data from a dataset to an xml file as a method of backup.I am trying to get the data deserialized back to the dataset.But for some reason, I cannot get the data to persist back to the DB.I don't receive any error messages either.The first chunk of code is the serialization code and the second chunk is the deserialization code.I can show that the deserialization back to the dataset is complete because this code in the 2nd block DataGridView2.DataSource = Movie_dbDataSet.movie_tb - displays the data in correct form all it is all there in the datagridview2.I call the update method but it does not get persisted back to the db.[code]
I'm seeing a strange build bug a lot. Sometimes after typing some code we receive the following build error.
Class 'clsX' must implement 'Event PropertyChanged(sender As Object, e As PropertyChangedEventArgs)' for interface System.ComponentModel.INotifyPropertyChanged'.
And
'PropertyChanged' cannot implement 'PropertyChanged' because there is no matching event on interface 'System.ComponentModel.INotifyPropertyChanged'.
Those error should never go together! Usually we can just ignore the exception and build the solution but often enough this bug stops our build. (this happens a lot using Edit and Continue which is annoying)Removing the PropertyChanged event and retyping the same code! sometimes fixes this.We're using a code generator that causes this error to surface but just editing some files manually triggers this exception too. This error occur's on multiple machines using various setups.
I'm making a control and I am trying to finalize my design time properties grid. I have several List(of Class) items as public properties and when I click on the design time menu (while testing the control) there is the word "Collection" and a button with an ellipsis (...) that brings up a neat pop up with the buttons Add/remove and all of the public properties of the collection's class on the right hand side. Basically for a non-collection instance of a class (with public properties) I'd like a similar button to show up. I know I could put all of the properties in the main control class and group them, but I like the pop up box feature. Anyway to duplicate this? (think font grid item etc.)
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?
I'm working on a Hazardous Materials label printing program. One of the options is to do an "NFPA" label. Since there are 4 values required with 4 or 6 options, the ratings are entered via radio buttons in a group box. That's working okay. I display values in the NFPA diamond as they're entered: left quadrant blue, top quadrant red, left yellow, bottom red. I'm having trouble with the label in which the rating will be displayed on top of a jpg diamond for the white. In this quadrant the text can be up to 4 characters. I can accept the text going into an adjacent block a little, but the corners of the label overlap into another quadrant/color. I reduced the font size which solved the overlap problem but the font is then too small and looks terrible. I tried to make the background of the label transparent to let the color come through correctly but that's not a valid value for label.background. I'm figuring that the transparent background is the best solution. What can I use that will accept a transparent background so the color shows through?
I'm trying to set the transparent property via label properties properties, not via code. Here's the code if it makes any difference:
Public Class NFPA Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Close() End Sub
How to change all properties of a form to properties of other but don't change important properties like Owner,Handle, OwnedForms, Parent,HasChildren,Controls and ... .I have a child form that i want it to provide controls of Form.The background form provides Aero frame and child form is a transparent form in it.I want it because I want to draw buttons with system style in Aero in Windows Forms.This is my own code but it does not work good (ForeForm is child form):
For Each Propertry In ForeForm.GetType.GetProperties() Select Case Propertry.Name Case "AeroBackgroundEnabled", "FormBorderStyle", "TransparencyKey", "Parent", "Owner", "ShowInTaskbar", "Handle", "HasChildren", "OwnedFo[code].....
Additionaly:I wrote a great Aero Form.I don't publish current version (1.2) that supports Aero Blur,RealTime Aero Color change,extend Basic theme?
I've read thru Iceplug's tutorial on control arrays and got it working. I tried to add a new event by basically copying his click event code and calling it a doubleclick event. I used the proper addhandler and assigned the correct name to my sub. I have the click event changing the background color to blue and the doubleclick event changing the background color to green. The background color does not change to green. Why?
Heres the tutorial with my new code encased in asterisks ...
I have my own class of graphic objects, and now I'd like to allow a user to right-click on one of those within the application and see a properties window. Is there a pre-built dialog or control for displaying properties at runtime? I'd like to have something just like the IDE properties window button for my application.
Public Class LOA Private Sub PrintDocument1_PrintPage(ByVal sender As System.Object, ByVal e As System.Drawing.Printing.PrintPageEventArgs) Handles PrintDocument1.PrintPage
I am using VB.NET for Windows applications. What is the difference between Load event,Activate event and Enter event in the Form and in which order the above event is executed.
I'm trying to validate a few things in a form I'm building. It has a datagrid with clients info (taken from an access database) and a few textboxes where the user can type some search criteria. The thing is that those same textboxes are used to add new clients to the database and to modify a client's information if one from the datagrid is selected, so I made it that the buttons to insert and modify clients are disabled on load and thenevery time the text on a textbox changes ("TextChanged" event) they become enabled. So far so good. But then I wanted to make it so when a client from the datagrid is selected both buttons become disabled again until the text on a textbox changes (to make sure they're adding a different client and not the same one that was selected).
I tried using the CellClick event from the datagrid to disable the buttons, but since every time a client is selected from the datagrid the info is shown on the textboxes, this triggers the TextChanged event too, and the buttons become available.So, is there a way I can tell the TextChanged event not to be triggered when the CellClick event occurs?
What I've done is create a User Control Library (Project) and I've added a single User Control to that project. The control contains a single FlowLayoutPanel, and I created a Property on the control itself to pass the FlowDirection from the Control to its FlowLayoutPanel child.
Build, reference, component appears in the Toolbox and everything works fine, but the property on the control does not appear in the Properties window when I go to edit it at design time.
I have a BLL class which contains properties for the fields in a Country table (CountryCode, CountryName, etc). It also has a property ioDAL, which is a reference to a DAL class (created with SubSonic 2.2), which has same named fields.
I have a LoadRecord() method which calls the DAL's FetchById() method that populates the DAL properties by calling the database (SQL Server 2005 FWIW).What I then want to do, rather than writing code to populate each BLL property from its DAL equivalent, is to use AutoMapper (from CodePlex). I think the line should be something like
Mapper.CreateMap(ioDAL, Me)()but this gives errors "Value of type (DAL class / namespace naming) cannot be converted to 'System.Type'" and "Value of type (BLL class / namespace naming) cannot be converted to 'System.Type'".
The event handlers in my parent class are never called though the events are raised in the child class.
The Code:
Public Class childForm Public Event checkboxchangedEvent(ByVal checkbox1 As Boolean, ByVal checkbox2 As Boolean) Private Sub checkboxchanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged, CheckBox2.CheckedChanged
I'm trying to complete this airline reservation application, but having a problem in this part of the question:Creat an event handler for the FlightBindingSource's PositionChanged event: select FlightBindingSource in the class Name combobox then select position changed in method name combobox to creat the FlightBindingSource's PositionChanged event handler. Write a code to access the currently displayed flight object and pass its flightNumber to method DisplayPassengers as a decimal.This Is my code so far:
HTML
Public Class AirlineReservationForm Private database As New ReservationsDataClassesDataContext() Private Sub FillAll()[code].....
