I am trying to make a开发者_Go百科 (very) simple Data Binding test, but it doesn't work as I expected... Say I have the following classes:
// this class represents some kind of data producer
public class DataSourceClass
{
public string Data { get; set; }
public DataSourceClass()
{ }
}
//this form holds the TextBox control as the Data consumer
public partial class DatabindingTestForm : Form
{
public DataSourceClass ds { get; set; }
public DatabindingTestForm()
{
InitializeComponent();
ds = new DataSourceClass();
textBox.DataBindings.Add("Text", ds, "Data");
}
private void checkBox_CheckedChanged(object sender, EventArgs e)
{
if (checkBox.Checked)
ds.Data = "CHECKED";
else
ds.Data = "NOT CHECKED";
}
}
I didn't add the designer code, but its there, and the form holds a TextBox object and a CheckBox object. As you can understand, I am trying to make the Textbox Text property change as the user checks \ unchecks the CheckBox. But this code doesn't update the TextBox Text property. Can someone please explain me what am I missing?
You need some way to notify WinForms when the value of the Data
property changes. The most straightforward way is to either:
- Add an event to
DataSourceClass
:public event EventHandler DataChanged;
- Make
DataSourceClass
implementINotifyPropertyChanged
. This gives you aPropertyChanged
event.
Either way you'll have a new event that you need to raise. You'll need to convert your Data
property from an auto property to one with a private field, a get
method and a set
method. Once you have an explicit getter and setter for the Data
property, you'll be able to raise your event from inside the setter.
You can use the INotifyPropertyChanged
interface. I didn't run this through the IDE/compiler so there could be a syntax error.
public class DataSourceClass : INotifyPropertyChanged
{
private string _data;
public string Data
{
get
{
return _data;
}
set
{
if( _data != value )
{
_data = value;
OnPropertyChanged( "data" );
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged( string propertyName )
{
PropertyChangedEventHandler handler = PropertyChanged;
if( handler != null )
{
handler( new PropertyChangedEventArgs( propertyName ) );
}
}
}
精彩评论