mcs/class/Managed.Windows.Forms/System.Windows.Forms/Binding.cs

   1 // Permission is hereby granted, free of charge, to any person obtaining
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   3 // "Software"), to deal in the Software without restriction, including
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   5 // distribute, sublicense, and/or sell copies of the Software, and to
   6 // permit persons to whom the Software is furnished to do so, subject to
   7 // the following conditions:
   8 //
   9 // The above copyright notice and this permission notice shall be
  10 // included in all copies or substantial portions of the Software.
  11 //
  12 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  13 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  14 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  15 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  16 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  17 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  18 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  19 //
  20 // Copyright (c) 2004-2005 Novell, Inc.
  21 //
  22 // Authors:
  23 //      Peter Bartok    pbartok@novell.com
  24 //      Jackson Harper  jackson@ximian.com
  25 //
  26
  27
  28 using System.ComponentModel;
  29
  30 namespace System.Windows.Forms {
  31
  32         [TypeConverter (typeof (ListBindingConverter))]
  33         public class Binding {
  34
  35                 private string property_name;
  36                 private object data_source;
  37                 private string data_member;
  38                 private BindingMemberInfo binding_member_info;
  39                 private Control control;
  40
  41                 private BindingManagerBase manager;
  42                 private PropertyDescriptor prop_desc;
  43                 private PropertyDescriptor is_null_desc;
  44
  45                 private EventDescriptor changed_event;
  46                 private EventHandler property_value_changed_handler;
  47                 private object event_current; // The manager.Current as far as the changed_event knows
  48
  49                 private object data;
  50                 private Type data_type;
  51
  52                 #region Public Constructors
  53                 public Binding (string propertyName, object dataSource, string dataMember)
  54                 {
  55                         property_name = propertyName;
  56                         data_source = dataSource;
  57                         data_member = dataMember;
  58                         binding_member_info = new BindingMemberInfo (dataMember);
  59                 }
  60                 #endregion      // Public Constructors
  61
  62                 #region Public Instance Properties
  63                 public BindingManagerBase BindingManagerBase {
  64                         get {
  65                                 return manager;
  66                         }
  67                 }
  68
  69                 public BindingMemberInfo BindingMemberInfo {
  70                         get {
  71                                 return binding_member_info;
  72                         }
  73                 }
  74
  75                 [DefaultValue (null)]
  76                 public Control Control {
  77                         get {
  78                                 return control;
  79                         }
  80                 }
  81
  82                 public object DataSource {
  83                         get {
  84                                 return data_source;
  85                         }
  86                 }
  87
  88                 [MonoTODO]
  89                 public bool IsBinding {
  90                         get {
  91                                 return false;
  92                         }
  93                 }
  94
  95                 [DefaultValue ("")]
  96                 public string PropertyName {
  97                         get {
  98                                 return property_name;
  99                         }
 100                 }
 101                 #endregion      // Public Instance Properties
 102
 103                 #region Protected Instance Methods
 104                 protected virtual void OnFormat (ConvertEventArgs cevent)
 105                 {
 106                         if (Format!=null)
 107                                 Format (this, cevent);
 108                 }
 109
 110                 protected virtual void OnParse (ConvertEventArgs cevent)
 111                 {
 112                         if (Parse!=null)
 113                                 Parse (this, cevent);
 114                 }
 115                 #endregion      // Protected Instance Methods
 116
 117
 118                 internal void SetControl (Control control)
 119                 {
 120                         if (control == this.control)
 121                                 return;
 122
 123                         prop_desc = TypeDescriptor.GetProperties (control).Find (property_name, false);
 124                         data_type = prop_desc.PropertyType; // Getting the PropertyType is kinda slow and it should never change, so it is cached
 125
 126                         if (prop_desc == null)
 127                                 throw new ArgumentException (String.Concat ("Cannot bind to property '", property_name, "' on target control."));
 128                         if (prop_desc.IsReadOnly)
 129                                 throw new ArgumentException (String.Concat ("Cannot bind to property '", property_name, "' because it is read only."));
 130
 131                         control.Validating += new CancelEventHandler (ControlValidatingHandler);
 132
 133                         this.control = control;
 134                 }
 135
 136                 internal void Check (BindingContext binding_context)
 137                 {
 138                         if (control == null)
 139                                 return;
 140
 141                         manager = control.BindingContext [data_source, property_name];
 142                         manager.AddBinding (this);
 143
 144                         WirePropertyValueChangedEvent ();
 145
 146                         is_null_desc = TypeDescriptor.GetProperties (manager.Current).Find (property_name + "IsNull", false);
 147
 148                         PullData ();
 149                 }
 150
 151                 internal void PushData ()
 152                 {
 153                         SetControlValue (data);
 154                 }
 155
 156                 internal void PullData ()
 157                 {
 158                         if (is_null_desc != null) {
 159                                 bool is_null = (bool) is_null_desc.GetValue (manager.Current);
 160                                 if (is_null) {
 161                                         data = Convert.DBNull;
 162                                         return;
 163                                 }
 164                         }
 165
 166                         PropertyDescriptor pd = TypeDescriptor.GetProperties (manager.Current).Find (data_member, true);
 167                         object pulled = pd.GetValue (manager.Current);
 168                         data = ParseData (pulled, pd.PropertyType);
 169
 170                         data = FormatData (data);
 171                         SetControlValue (data);
 172                 }
 173
 174                 internal void UpdateIsBinding ()
 175                 {
 176                         PushData ();
 177                 }
 178
 179                 private void SetControlValue (object data)
 180                 {
 181                         prop_desc.SetValue (control, data);
 182                 }
 183
 184                 private void CurrentChangedHandler ()
 185                 {
 186                         if (changed_event != null) {
 187                                 changed_event.RemoveEventHandler (event_current, property_value_changed_handler);
 188                                 WirePropertyValueChangedEvent ();
 189                         }
 190                 }
 191
 192                 private void WirePropertyValueChangedEvent ()
 193                 {
 194                         EventDescriptor changed_event = TypeDescriptor.GetEvents (manager.Current).Find (property_name + "Changed", false);
 195                         if (changed_event == null)
 196                                 return;
 197                         property_value_changed_handler = new EventHandler (PropertyValueChanged);
 198                         changed_event.AddEventHandler (manager.Current, property_value_changed_handler);
 199
 200                         event_current = manager.Current;
 201                 }
 202
 203                 private void PropertyValueChanged (object sender, EventArgs e)
 204                 {
 205                         PullData ();
 206                 }
 207
 208                 private void ControlValidatingHandler (object sender, CancelEventArgs e)
 209                 {
 210                         PullData ();
 211                 }
 212
 213                 private object ParseData (object data, Type data_type)
 214                 {
 215                         ConvertEventArgs e = new ConvertEventArgs (data, data_type);
 216
 217                         OnParse (e);
 218                         if (e.Value.GetType ().IsAssignableFrom (data_type))
 219                                 return e.Value;
 220                         if (e.Value == Convert.DBNull)
 221                                 return e.Value;
 222
 223                         return ConvertData (e.Value, data_type);
 224                 }
 225
 226                 private object FormatData (object data)
 227                 {
 228                         if (data_type == typeof (object))
 229                                 return data;
 230
 231                         ConvertEventArgs e = new ConvertEventArgs (data, data_type);
 232
 233                         OnFormat (e);
 234                         if (e.Value.GetType ().IsAssignableFrom (data_type))
 235                                 return e.Value;
 236
 237                         return ConvertData (data, data_type);
 238                 }
 239
 240                 private object ConvertData (object data, Type data_type)
 241                 {
 242                         TypeConverter converter = TypeDescriptor.GetConverter (data.GetType ());
 243                         if (converter != null && converter.CanConvertTo (data_type))
 244                                 return converter.ConvertTo (data, data_type);
 245
 246                         if (data is IConvertible) {
 247                                 object res = Convert.ChangeType (data, data_type);
 248                                 if (res.GetType ().IsAssignableFrom (data_type))
 249                                         return res;
 250                         }
 251
 252                         return null;
 253                 }
 254
 255                 #region Events
 256                 public event ConvertEventHandler Format;
 257                 public event ConvertEventHandler Parse;
 258                 #endregion      // Events
 259         }
 260 }