CODEWITHSUNDEEP
c#winformsdata-binding
jac
jac

Reputation: 9726

Bound UserControl is not updating data source

I have a UserControl that has a Textbox, Button, and a Tooltip controls on it. It does implement INotifyPropertyChanged I have tried overriding the Text property and adding my own property, but in all cases the control reads from the bound data source fine, but never updates the data source. My events are raised when the text is changed. Some of the code is below. All other standard controls are working fine. What do I need to get the control to update the data source when the user has entered or changed the value?

public partial class UrlControl : UserControl, INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    [Bindable(true)]
    [Browsable(true)]
    public string Url
    {
        get
        {
            return url.Text;
        }
        set
        {
            if (value != url.Text)
            {
                url.Text = value;
                OnPropertyChanged("Url");
            }
        }
    }
    protected virtual void OnPropertyChanged(string propertyName)
    {
        OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
    }

    protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, e);
        }
    }

This is the binding code from the form designer.

this.urlControl1.DataBindings.Add(new System.Windows.Forms.Binding("Url", this.customerBindingSource, "First", true, System.Windows.Forms.DataSourceUpdateMode.OnPropertyChanged));

}

Upvotes: 3

Views: 2650

Answers (2)

Reddog
Reddog

Reputation: 15579

This should work well for reading values from the datasource.

However, when it comes to writing values to the datasource it looks like you're storing and getting the Url value directly from the url textbox. However, you're not raising property change notifications when the textbox's text is changed within the UI. To fix this, add a TextChanged event handler on the textbox, which can simple call:

void url_TextChanged(object sender, EventArgs e)
{
    OnPropertyChanged("Url");
    OnUrlChanged(); // See additional note below
}

As a side, although implementing INotifyPropertyChanged should work... When it comes to Windows Forms binding you can also create an event with the property name suffixed with "Changed" and the binding should watch that:

public event EventHandler UrlChanged;

protected virtual void OnUrlChanged()
{
    var handler = UrlChanged;
    if (handler != null)
    {
        handler(this, EventArgs.Empty);
    }
}

[Bindable(true)]
[Browsable(true)]
public string Url
{
    get
    {
        return url.Text;
    }
    set
    {
        if (value != url.Text)
        {
            url.Text = value;
            OnPropertyChanged("Url");
            OnUrlChanged();
        }
    }
}

Upvotes: 1

Igby Largeman
Igby Largeman

Reputation: 16747

INotifyPropertyChanged is for datasources. It allows your datasource to notify bound controls and other listeners of property changes. However, controls themselves use a different mechanism. It's a bit strange: you create events on your control with the naming convention <PropertyName>Changed. When the value of a property changes, you raise the associated event.

Example:

public string Url
{
    get { return url.Text; }
    set 
    { 
        if (value != url.Text) 
        { 
            url.Text = value; 
            OnUrlChanged(); // raise event
        }
    }
}

public event EventHandler UrlChanged;

private void OnUrlChanged()
{
    // raise the UrlChanged event
    if (UrlChanged != null)
        UrlChanged(this, new EventArgs());
}

That's all you need to do. The Databinding Fairies will see that event and hook it up when you create the binding.

Here's the topic on MSDN: How to: Apply the PropertyNameChanged Pattern

Upvotes: 5

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