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

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   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                 public bool IsBinding {
  89                         get {
  90                                 if (control == null || !control.Created)
  91                                         return false;
  92                                 if (manager == null || manager.IsSuspended)
  93                                         return false;
  94                                 return true;
  95                         }
  96                 }
  97
  98                 [DefaultValue ("")]
  99                 public string PropertyName {
 100                         get {
 101                                 return property_name;
 102                         }
 103                 }
 104                 #endregion      // Public Instance Properties
 105
 106                 #region Protected Instance Methods
 107                 protected virtual void OnFormat (ConvertEventArgs cevent)
 108                 {
 109                         if (Format!=null)
 110                                 Format (this, cevent);
 111                 }
 112
 113                 protected virtual void OnParse (ConvertEventArgs cevent)
 114                 {
 115                         if (Parse!=null)
 116                                 Parse (this, cevent);
 117                 }
 118                 #endregion      // Protected Instance Methods
 119
 120
 121                 internal void SetControl (Control control)
 122                 {
 123                         if (control == this.control)
 124                                 return;
 125
 126                         prop_desc = TypeDescriptor.GetProperties (control).Find (property_name, false);
 127                         data_type = prop_desc.PropertyType; // Getting the PropertyType is kinda slow and it should never change, so it is cached
 128
 129                         if (prop_desc == null)
 130                                 throw new ArgumentException (String.Concat ("Cannot bind to property '", property_name, "' on target control."));
 131                         if (prop_desc.IsReadOnly)
 132                                 throw new ArgumentException (String.Concat ("Cannot bind to property '", property_name, "' because it is read only."));
 133
 134                         control.Validating += new CancelEventHandler (ControlValidatingHandler);
 135
 136                         this.control = control;
 137                 }
 138
 139                 internal void Check (BindingContext binding_context)
 140                 {
 141                         if (control == null)
 142                                 return;
 143
 144                         manager = control.BindingContext [data_source, property_name];
 145                         manager.AddBinding (this);
 146
 147                         WirePropertyValueChangedEvent ();
 148
 149                         is_null_desc = TypeDescriptor.GetProperties (manager.Current).Find (property_name + "IsNull", false);
 150
 151                         PullData ();
 152                 }
 153
 154                 internal void PushData ()
 155                 {
 156                         data = prop_desc.GetValue (control);
 157                         data = FormatData (data);
 158                         SetPropertyValue (data);
 159                 }
 160
 161                 internal void PullData ()
 162                 {
 163                         if (is_null_desc != null) {
 164                                 bool is_null = (bool) is_null_desc.GetValue (manager.Current);
 165                                 if (is_null) {
 166                                         data = Convert.DBNull;
 167                                         return;
 168                                 }
 169                         }
 170
 171                         if (data_member != null) {
 172                                 PropertyDescriptor pd = TypeDescriptor.GetProperties (manager.Current).Find (data_member, true);
 173                                 object pulled = pd.GetValue (manager.Current);
 174                                 data = ParseData (pulled, pd.PropertyType);
 175                         } else {
 176                                 object pulled = manager.Current;
 177                                 data = ParseData (pulled, pulled.GetType ());
 178                         }
 179
 180                         data = FormatData (data);
 181                         SetControlValue (data);
 182                 }
 183
 184                 internal void UpdateIsBinding ()
 185                 {
 186                         PushData ();
 187                 }
 188
 189                 private void SetControlValue (object data)
 190                 {
 191                         prop_desc.SetValue (control, data);
 192                 }
 193
 194                 private void SetPropertyValue (object data)
 195                 {
 196                         PropertyDescriptor pd = TypeDescriptor.GetProperties (manager.Current).Find (data_member, true);
 197                         if (pd.IsReadOnly)
 198                                 return;
 199                         pd.SetValue (manager.Current, data);
 200                 }
 201
 202                 private void CurrentChangedHandler ()
 203                 {
 204                         if (changed_event != null) {
 205                                 changed_event.RemoveEventHandler (event_current, property_value_changed_handler);
 206                                 WirePropertyValueChangedEvent ();
 207                         }
 208                 }
 209
 210                 private void WirePropertyValueChangedEvent ()
 211                 {
 212                         EventDescriptor changed_event = TypeDescriptor.GetEvents (manager.Current).Find (property_name + "Changed", false);
 213                         if (changed_event == null)
 214                                 return;
 215                         property_value_changed_handler = new EventHandler (PropertyValueChanged);
 216                         changed_event.AddEventHandler (manager.Current, property_value_changed_handler);
 217
 218                         event_current = manager.Current;
 219                 }
 220
 221                 private void PropertyValueChanged (object sender, EventArgs e)
 222                 {
 223                         PullData ();
 224                 }
 225
 226                 private void ControlValidatingHandler (object sender, CancelEventArgs e)
 227                 {
 228                         PullData ();
 229                 }
 230
 231                 private object ParseData (object data, Type data_type)
 232                 {
 233                         ConvertEventArgs e = new ConvertEventArgs (data, data_type);
 234
 235                         OnParse (e);
 236                         if (data_type.IsAssignableFrom (e.Value.GetType ()))
 237                                 return e.Value;
 238                         if (e.Value == Convert.DBNull)
 239                                 return e.Value;
 240
 241                         return ConvertData (e.Value, data_type);
 242                 }
 243
 244                 private object FormatData (object data)
 245                 {
 246                         if (data_type == typeof (object))
 247                                 return data;
 248
 249                         ConvertEventArgs e = new ConvertEventArgs (data, data_type);
 250
 251                         OnFormat (e);
 252                         if (data_type.IsAssignableFrom (e.Value.GetType ()))
 253                                 return e.Value;
 254
 255                         return ConvertData (data, data_type);
 256                 }
 257
 258                 private object ConvertData (object data, Type data_type)
 259                 {
 260                         TypeConverter converter = TypeDescriptor.GetConverter (data.GetType ());
 261                         if (converter != null && converter.CanConvertTo (data_type))
 262                                 return converter.ConvertTo (data, data_type);
 263
 264                         if (data is IConvertible) {
 265                                 object res = Convert.ChangeType (data, data_type);
 266                                 if (data_type.IsAssignableFrom (res.GetType ()))
 267                                         return res;
 268                         }
 269
 270                         return null;
 271                 }
 272
 273                 #region Events
 274                 public event ConvertEventHandler Format;
 275                 public event ConvertEventHandler Parse;
 276                 #endregion      // Events
 277         }
 278 }