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Passing Value on Property Change

I have 2 forms: Form A and Form B. I also have a property field class.
Form A contains the label I want changed when a property is changed. Form B contains code that will change the property field.
Property Class Code:
public class Controller
{
private static string _customerID;
public static string customerID
{
get { return _customerID; }
set
{
_customerID = value;
if (_customerID != "")
{
FormA.ChangeMe();
}
}
}
}
Form B Code:
private void something_Click(object sender, SomethingEventArgs e) {
Controller.customerID = "Cool";
}
Form A Code:
public static void ChangeMe()
{
var frmA = new FormA();
MessageBox.Show("Test: " + Controller.customerID); //This works! Shows Cool
frmA.lb2Change.Text = Controller.customerID; //This kind of works..
MessageBox.Show("Test2: " + frmA.lb2Change.Text); //This shows the correct value. Shows Cool
}
The property field value is passed (which I know from the MessageBox) however it does not update the value on the form label itself. Why is this? What am I doing wrong? I also believe there is a better alternative for achieving what ChangeMe() method is intended to achieve -- if so are there any suggestions?

You can do the following
To define a delegate
To Implement Property Change Notification
Delegate
public delegate void OnCustomerIDChanging(object sender,CancelEventArgs e);
public delegate void OnCustomerIDChanged(object sender,object value);
public class Controller
{
private static string _customerID;
public event OnCustomerIDChanging CustoerIDChanging;
public event OnCustomerIDChanged CustoerIDChanged;
public static string customerID
{
get { return _customerID; }
set
{
// make sure that the value has a `value` and different from `_customerID`
if(!string.IsNullOrEmpty(value) && _customerID!=value)
{
if(CustomerIDChanging!=null)
{
var state = new CancelEventArgs();
// raise the event before changing and your code might reject the changes maybe due to violation of validation rule or something else
CustomerIDChanging(this,state);
// check if the code was not cancelled by the event from the from A
if(!state.Cancel)
{
// change the value and raise the event Changed
_customerID = value;
if(CustomerIDChanged!=null)
CustomerIDChanged(this,value);
}
}
}
}
}
}
in your Form and when you are initiating the Controller Object
var controller = new Controller();
controller.CustomerIDChanging +=(sd,args) =>{
// here you can test if you want really to change the value or not
// in case you want to reject the changes you can apply
args.Cancel = true;
};
controller.CustomerIDChanged +=(sd,args) =>{
// here you implement the code **Changed already**
}
The above code will give you a great control over your code, also will make your controller code reusable and clean. Same
result you can get by implementing INotifyPropertyChanged interface
INotifyPropertyChanged
you might have a look on this article to get more information

In your static method ChangeMe you are creating a new Form every time, you want to Change the value. Instead of that you want to change the value of an existing form. Therefor your Controller needs an instance of this FormA. Try it like this:
public class Controller
{
//You can pass the form throught the constructor,
//create it in constructor, ...
private FormA frmA;
private string _customerID;
public string customerID
{
get { return _customerID; }
set
{
_customerID = value;
if (_customerID != "")
{
frmA.ChangeMe();
}
}
}
}
Now you don´t need to be static in your FormA:
public void ChangeMe()
{
MessageBox.Show("Test: " + Controller.customerID);
this.lb2Change.Text = Controller.customerID;
}

Object loses data after initialization

I have these objects in my project:
SchedulerList
SchedulerListItem
SchedulerListItemDetails
each one is a win forms control, which are used in forms of my application. The SchedulerList holds SchedulerListItems and each item can have SchedulerListItemDetails.
my code goes as follows:
//creating my initial list form
FrmListTesting f = new FrmListTesting();
f.Show();
The form has only one button that has a hard-coded parameter for testing purposes, as well as a SchedulerList control taht will hold the list items.
When the button is clicked the form does the following:
private void button1_Click(object sender, EventArgs e)
{
var control = this.Controls[1] as SchedulerList;
var path = #"D:\Share\Countries.txt";
var sli = new SchedulerListItem(path);
control.AddItem(sli);
}
my SchedulerListItem constuctor goes as follows:
public SchedulerListItem(string path)
{
InitializeComponent();
this.Name = Path.GetFileNameWithoutExtension(path);
this.SourcePath = path;
this.DestinationPath = GetDestinationPath(path);
}
And the AddItem method is defined as:
public void AddItem(SchedulerListItem item)
{
this.flPanel.Controls.Add(item);
}
The add item method works as intended, displays all the data that was required and displays it in the UI. The list item has a button that brings up the details form as such:
//the form constructor
public FrmSchedulerItemDetails(SchedulerListItem item)
{
InitializeComponent();
this.detailsControl = new SchedulerListItemDetails(item, this);
}
//control constructor
public SchedulerListItemDetails(SchedulerListItem item, Form owner)
{
InitializeComponent();
this.SourcePath = item.SourcePath;
this.DestinationPath = item.DestinationPath;
this.OldFormat = item.OldFormat;
this.ExportToExcel = item.ExportToExcel;
this.owner = owner;
this.underlyingItem = item;
}
And now the problem. After the SchedulerListItemDetails constructor is called and the data "gets initialized", when i look at the data inside the object its set to default values. it seams that everything that I set after InitializeComponent(); gets ignored.
things that i have tried:
hard-coding the values to see if primitives get passed correctly
settings breakpoints on every InitializeComponent() method to see the stack trace associated with setting to default values
none of the methods show any results... I know that if i use a form directly instead of using a control within a from i can set the values the way i want to, but I'm very confused as to why this other method with controls doesn't work.
EDIT 1:
the code for SchedulerListItemDetails:
public partial class SchedulerListItemDetails : UserControl
{
public SchedulerListItemDetails(SchedulerListItem item, Form owner)
{
InitializeComponent();
this.SourcePath = item.SourcePath;
this.DestinationPath = item.DestinationPath;
this.OldFormat = item.OldFormat;
this.ExportToExcel = item.ExportToExcel;
this.owner = owner;
this.underlyingItem = item;
}
public SchedulerListItemDetails()
{
InitializeComponent();
}
private Form owner = null;
private SchedulerListItem underlyingItem;
public Boolean ExportToExcel
{
get
{
return this.cbxExcel.Checked;
}
set
{
this.cbxExcel.Checked = value;
}
}
public Boolean OldFormat
{
get
{
return this.cbxOldFormat.Checked;
}
set
{
this.cbxOldFormat.Checked = value;
}
}
public String DestinationPath
{
get
{
return this.tbxDestinationPath.Text;
}
set
{
this.tbxDestinationPath.Text = value;
}
}
public String SourcePath
{
get
{
return this.tbxSourcePath.Text;
}
set
{
this.tbxSourcePath.Text = value;
}
}
private void btnCancel_Click(object sender, EventArgs e)
{
this.owner.Close();
}
private void btnSave_Click(object sender, EventArgs e)
{
underlyingItem.SourcePath = this.SourcePath;
underlyingItem.DestinationPath = this.DestinationPath;
underlyingItem.OldFormat = this.OldFormat;
underlyingItem.ExportToExcel = this.ExportToExcel;
btnCancel_Click(sender, e);
}
}

I'll make an answer, because it should help you to solve your problem.
You have default (parameterless) constructor, which may be called and if it is called, then your constructor with parameters is not called.
Proper design would be something like
public partial class SchedulerListItemDetails : UserControl
{
public SchedulerListItemDetails()
{
InitializeComponent();
}
public SchedulerListItemDetails(SchedulerListItem item, Form owner): this()
{
this.SourcePath = item.SourcePath;
...
}
}
Notice this(), this ensure what parameterless constructor is called before (and InitializeComponent() as well, no need to duplicate it in another constructor).
Back to your problem. In your case it's like this
public partial class SchedulerListItemDetails : UserControl
{
public SchedulerListItemDetails()
{
InitializeComponent();
}
public SchedulerListItemDetails(SchedulerListItem item, Form owner)
{
InitializeComponent();
this.SourcePath = item.SourcePath;
...
}
}
Only one constructor can be called. So if you put breakpoint in parameterless one and it's triggered, then you have problems. Because you create somewhere SchedulerListItemDetails without setting it's properties (they stay default).
More likely problem is that you create new instance of that object (either before or after constructing proper, if your code ever construct such object) and that instance is what you inspect later.

So after i got a quick course of how win forms work i figured out what the problem was.
my code that i thought was enough is:
public FrmSchedulerItemDetails(SchedulerListItem item)
{
InitializeComponent();
this.DetailsControl = new SchedulerListItemDetails(item, this);
}
public SchedulerListItemDetails DetailsControl
{
get
{
return this.detailsControl;
}
set
{
this.detailsControl = value;
}
}
the this.detailsControl is the control im trying to setup, but as i have learned the correct way of replacing a component for a new one is:
public FrmSchedulerItemDetails(SchedulerListItem item)
{
InitializeComponent();
this.DetailsControl = new SchedulerListItemDetails(item, this);
}
public SchedulerListItemDetails DetailsControl
{
get
{
return this.detailsControl;
}
set
{
this.Controls.Remove(this.detailsControl);
this.detailsControl = value;
this.Controls.Add(this.detailsControl);
}
}
Feel kinda silly now :).

Binding Label to a static string

I have made a Base Form which is inherited by most Forms in the application. Base form contains a Status Bar Control that displays user name which is internally a static string. User can Switch User at any point in the application by pressing a button on status bar. At this point the user name in the status bar should also change, as if now it only changes in code and UI has no idea about the change. I have googled around and found that i need to bind the label with that static string by implementing a INotifyProperty Interface. I have implemented many example code without success.
Appreciate any help

use BindableAttribute for the property you want to bind a control to it.
[Bindable(true)]
public int Username {
get {
// Insert code here.
return 0;
}
set {
// Insert code here.
}
}

You must implement a class to notify prop changed and therefore the prop can not be static. Combine with a singleton pattern and you have yout solution.
public class Global : INotifyPropertyChanged
{
private string _userName;
public string UserName
{
get
{
return this._userName;
}
set
{
if (this._userName == value)
{
return;
}
this._userName = value;
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs("UserName"));
}
{
}
public event PropertyChangedEventHandler PropertyChanged;
private Global() {}
public static readonly Global Get = new Global();
}
Usage:
var currUserName = Global.Get.UserName;
Global.Get.PropertyChanged += (s, e) => Console.WriteLine(e.PropertyName);
Global.Get.UserName = "John";
And bind to Global.Get to property UserName.

I would:
1- Add a timer to the base form to update the status bar. (the timer resolution is uo to your requirement).
the timer Tick handler would be something like this:
private void timerStatusUpdate_Tick(object sender, EventArgs e)
{
toolStripStatusLabelMessage.Text = StatusMessage();
}
2 - Add a virtual StatusMessage method to your base class:
class BaseForm : Form
{
.......
public virtual string StatusMessage()
{
return "override me!";
}
}
3- override StatusMessage in all your derived classes
class XXXForm : BaseForm
{
........
public override string StatusMessage()
{
return "XXXForm status message";
}
}

I use Reactive Extensions for these things
For example if you have a Context class with a property UserName
you could do this
public static class Context
{
public static Subject<string> UserChanged = new Subject<string>();
private static string user;
public static string User
{
get { return user; }
set
{
if (user != value)
{
user = value;
UserChanged.OnNext(user);
}
}
}
}
And then on your forms just do
Context.UserChanged.ObserveOn(SynchronizationContext.Current)
.Subscribe(user => label.Text = user);
The ObserveOn(SynchronizationContext.Current) makes it safe for cross thread operation calls

change label text in usercontrol at run time

hello
i m new to c# and im working on a project,in which i made a usercontrol1 as
*label textbox datepicker*now i wnt to change the label text,i m trying this code but it is not working
using System;
using System.Windows.Forms;
namespace library_system
{
public partial class UserControl1 : UserControl
{
public UserControl1()
{
InitializeComponent();
}
// private string DateLabel
public string DateLabel
{
**get { return DateLabel.Text; }//error when i write dateLabel.Text
set
{
DateLabel.Text= value;//error datelabel.Text
}**
}
i m using this code in usercontrol for is it right to do this way??
and in the main form i m writing code as
userControl11.DateLabel="From Date";//on for load event??Is this Right
Thanks in advance!!

You are writing a property and setting itself.
If your label name is lbl you could simply use lbl.Text="what you want";
If you need a property to have a stronger check on text, you could write:
public string DateLabel
{
get { return lbl.Text; }
set { lbl.Text = value; }
}
So in main form you could write (suppose you have a control named uc)
uc.DateLabel = "hello";
EDITED
To be clear: suppose you have
one label named lbl in your UserControl1 user control
a UserControl1 control in your main form named uc
In your user control code you can write:
public string DateLabel
{
get { return lbl.Text; }
set { lbl.Text = value; }
}
In your main form you can then write:
uc.DateLabel = "what you want";

Try changing it to this (controlname is id you have given to your label)
public string DateLabel
{
get { return controlname.Text; }
set
{
controlname.Text= value;
}
}

Your Property is Called DateLabel, and you are trying to set it.
That doesnt make sense.
Try the following. You will need to drag a asp:Label onto you usercontrol and call it lblDateLabel.
public string DateLabel
{
get { return lblDateLabel.Text; }
set { lblDateLabel.Text= value; }
}

C# Property Grid

I am writing an application which is going to allows users to change the properties of a text box or label and these controls are user controls. Would it be easiest to create a separate class for each user control which implements the properties I want them to be able to change and then bind those back to the user control? Or is there another method I am overlooking?

Create a custom Attribute, and tag the properties you want the user to edit with this attribute. Then set the BrowsableAttribute property on the property grid to a collection containing only your custom attribute:
public class MyForm : Form
{
private PropertyGrid _grid = new PropertyGrid();
public MyForm()
{
this._grid.BrowsableAttributes = new AttributeCollection(new UserEditableAttribute());
this._grid.SelectedObject = new MyControl();
}
}
public class UserEditableAttribute : Attribute
{
}
public class MyControl : UserControl
{
private Label _label = new Label();
private TextBox _textBox = new TextBox();
[UserEditable]
public string Label
{
get
{
return this._label.Text;
}
set
{
this._label.Text = value;
}
}
[UserEditable]
public string Value
{
get
{
return this._textBox.Text;
}
set
{
this._textBox.Text = value;
}
}
}