path: root/mcs/class/Managed.Windows.Forms/System.Windows.Forms/Binding.cs

// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
// Copyright (c) 2004-2005 Novell, Inc.
//
// Authors:
//	Peter Bartok	pbartok@novell.com
//	Jackson Harper	jackson@ximian.com
//


using System.ComponentModel;

namespace System.Windows.Forms {

	[TypeConverter (typeof (ListBindingConverter))]
	public class Binding {

		private string property_name;
		private object data_source;
		private string data_member;
		private BindingMemberInfo binding_member_info;
		private Control control;

		private BindingManagerBase manager;
		private PropertyDescriptor prop_desc;
		private PropertyDescriptor is_null_desc;

		private EventDescriptor changed_event;
		private EventHandler property_value_changed_handler;
		private object event_current; // The manager.Current as far as the changed_event knows

		private object data;
		private Type data_type;

		#region Public Constructors
		public Binding (string propertyName, object dataSource, string dataMember)
		{
			property_name = propertyName;
			data_source = dataSource;
			data_member = dataMember;
			binding_member_info = new BindingMemberInfo (dataMember);
		}
		#endregion	// Public Constructors

		#region Public Instance Properties
		public BindingManagerBase BindingManagerBase {
			get {
				return manager;
			}
		}

		public BindingMemberInfo BindingMemberInfo {
			get {
				return binding_member_info;
			}
		}

		[DefaultValue (null)]
		public Control Control {
			get {
				return control;
			}
		}

		public object DataSource {
			get {
				return data_source;
			}
		}

		public bool IsBinding {
			get {
				if (control == null || !control.Created)
					return false;
				if (manager == null || manager.IsSuspended)
					return false;
				return true;
			}
		}

		[DefaultValue ("")]
		public string PropertyName {
			get {
				return property_name;
			}
		}
		#endregion	// Public Instance Properties

		#region Protected Instance Methods
		protected virtual void OnFormat (ConvertEventArgs cevent)
		{
			if (Format!=null)
				Format (this, cevent);
		}

		protected virtual void OnParse (ConvertEventArgs cevent)
		{
			if (Parse!=null)
				Parse (this, cevent);
		}
		#endregion	// Protected Instance Methods

		
		internal void SetControl (Control control)
		{
			if (control == this.control)
				return;

			prop_desc = TypeDescriptor.GetProperties (control).Find (property_name, true);			
			
			if (prop_desc == null)
				throw new ArgumentException (String.Concat ("Cannot bind to property '", property_name, "' on target control."));
			if (prop_desc.IsReadOnly)
				throw new ArgumentException (String.Concat ("Cannot bind to property '", property_name, "' because it is read only."));
				
			data_type = prop_desc.PropertyType; // Getting the PropertyType is kinda slow and it should never change, so it is cached
			control.Validating += new CancelEventHandler (ControlValidatingHandler);

			this.control = control;
		}

		internal void Check (BindingContext binding_context)
		{
			if (control == null)
				return;

			manager = control.BindingContext [data_source];
			manager.AddBinding (this);

			WirePropertyValueChangedEvent ();

			is_null_desc = TypeDescriptor.GetProperties (manager.Current).Find (property_name + "IsNull", false);

			PullData ();
		}

		internal void PushData ()
		{
			if (IsBinding == false)
				return;

			data = prop_desc.GetValue (control);
			data = FormatData (data);
			SetPropertyValue (data);
		}

		internal void PullData ()
		{
			if (IsBinding == false)
				return;

			if (is_null_desc != null) {
				bool is_null = (bool) is_null_desc.GetValue (manager.Current);
				if (is_null) {
					data = Convert.DBNull;
					return;
				}
			}

			if (data_member != null) {
				PropertyDescriptor pd = TypeDescriptor.GetProperties (manager.Current).Find (data_member, true);
				object pulled = pd.GetValue (manager.Current);
				data = ParseData (pulled, pd.PropertyType);
			} else {
				object pulled = manager.Current;
				data = ParseData (pulled, pulled.GetType ());
			}

			data = FormatData (data);
			SetControlValue (data);
		}

		internal void UpdateIsBinding ()
		{
			PushData ();
		}

		private void SetControlValue (object data)
		{
			prop_desc.SetValue (control, data);
		}

		private void SetPropertyValue (object data)
		{
			PropertyDescriptor pd = TypeDescriptor.GetProperties (manager.Current).Find (data_member, true);
			if (pd.IsReadOnly)
				return;
			pd.SetValue (manager.Current, data);
		}

		private void CurrentChangedHandler ()
		{
			if (changed_event != null) {
				changed_event.RemoveEventHandler (event_current, property_value_changed_handler);
				WirePropertyValueChangedEvent ();
			}
		}

		private void WirePropertyValueChangedEvent ()
		{
			EventDescriptor changed_event = TypeDescriptor.GetEvents (manager.Current).Find (property_name + "Changed", false);
			if (changed_event == null)
				return;
			property_value_changed_handler = new EventHandler (PropertyValueChanged);
			changed_event.AddEventHandler (manager.Current, property_value_changed_handler);

			event_current = manager.Current;
		}

		private void PropertyValueChanged (object sender, EventArgs e)
		{
			PullData ();
		}

		private void ControlValidatingHandler (object sender, CancelEventArgs e)
		{
			PullData ();
		}

		private object ParseData (object data, Type data_type)
		{
			ConvertEventArgs e = new ConvertEventArgs (data, data_type);

			OnParse (e);
			if (data_type.IsInstanceOfType (e.Value))
				return e.Value;
			if (e.Value == Convert.DBNull)
				return e.Value;

			return ConvertData (e.Value, data_type);
		}

		private object FormatData (object data)
		{
			if (data_type == typeof (object)) 
				return data;

			ConvertEventArgs e = new ConvertEventArgs (data, data_type);

			OnFormat (e);
			if (data_type.IsInstanceOfType (e.Value))
				return e.Value;

			return ConvertData (data, data_type);
		}

		private object ConvertData (object data, Type data_type)
		{
			TypeConverter converter = TypeDescriptor.GetConverter (data.GetType ());
			if (converter != null && converter.CanConvertTo (data_type))
				return converter.ConvertTo (data, data_type);

			if (data is IConvertible) {
				object res = Convert.ChangeType (data, data_type);
				if (data_type.IsInstanceOfType (res))
					return res;
			}

			return null;
		}

		#region Events
		public event ConvertEventHandler Format;
		public event ConvertEventHandler Parse;
		#endregion	// Events
	}
}