.NET Databinding ignores property changes
I wrote a control in C # that comes from System.Windows.Forms.Control. I added a Selected property to which I want to bind data to a business object using a BindingSource.
I've implemented the PropertyNameChanged pattern by adding a SelectedChanged event that I fire when the Selected property changes.
This is my code:
public partial class RateControl : Control
{
[Category("Property Changed")]
public event EventHandler SelectedChanged;
public int Selected
{
get
{ return m_selected; }
set
{
if (m_selected != value)
{
m_selected = value;
OnSelectedChanged();
Invalidate();
}
}
}
protected virtual void OnSelectedChanged()
{
if (this.SelectedChanged != null)
this.SelectedChanged(this, new EventArgs());
}
}
When I bind to the Selected property, I can see that the event is pegged. The event is also triggered when the property changes.
However, the business object is not updated. I don't even see access to the getter of the Selected property.
What am I missing?
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Do you have the binding mode set to DataSourceUpdateMode.OnPropertyChanged? Either through binding.DataSourceUpdateMode = DataSourceUpdateMode.OnPropertyChanged;
or using one of the overloads DataBindings.Add(...)
.
The following works for me to pass values to a business object ...
using System;
using System.Diagnostics;
using System.Windows.Forms;
class MyForm : Form
{
public MyForm()
{
MyBusinessObject obj = new MyBusinessObject();
Button btn = new Button();
btn.Click += delegate { Foo++; };
DataBindings.Add("Foo", obj, "Bar", false, DataSourceUpdateMode.OnPropertyChanged);
DataBindings.Add("Text", obj, "Bar");
Controls.Add(btn);
}
private int foo;
public event EventHandler FooChanged;
public int Foo
{
get { return foo; }
set
{
if (foo != value)
{
foo = value;
Debug.WriteLine("Foo changed to " + foo);
if (FooChanged != null) FooChanged(this, EventArgs.Empty);
}
}
}
}
class MyBusinessObject
{
private int bar;
public event EventHandler BarChanged;
public int Bar
{
get { return bar; }
set
{
if (bar != value)
{
bar = value;
Debug.WriteLine("Bar changed to " + bar);
if (BarChanged != null) BarChanged(this, EventArgs.Empty);
}
}
}
}
static class Program
{
[STAThread]
static void Main()
{
Application.Run(new MyForm());
}
}
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