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
  39                 private BindingMemberInfo binding_member_info;
  40                 private Control control;
  41
  42                 private BindingManagerBase manager;
  43                 private PropertyDescriptor control_property;
  44                 private PropertyDescriptor is_null_desc;
  45
  46                 private EventDescriptor changed_event;
  47                 private EventHandler property_value_changed_handler;
  48                 private object event_current; // The manager.Current as far as the changed_event knows
  49
  50                 private object data;
  51                 private Type data_type;
  52
  53                 #region Public Constructors
  54                 public Binding (string propertyName, object dataSource, string dataMember)
  55                 {
  56                         property_name = propertyName;
  57                         data_source = dataSource;
  58                         data_member = dataMember;
  59                         binding_member_info = new BindingMemberInfo (dataMember);
  60                 }
  61                 #endregion      // Public Constructors
  62
  63                 #region Public Instance Properties
  64                 public BindingManagerBase BindingManagerBase {
  65                         get {
  66                                 return manager;
  67                         }
  68                 }
  69
  70                 public BindingMemberInfo BindingMemberInfo {
  71                         get {
  72                                 return binding_member_info;
  73                         }
  74                 }
  75
  76                 [DefaultValue (null)]
  77                 public Control Control {
  78                         get {
  79                                 return control;
  80                         }
  81                 }
  82
  83                 public object DataSource {
  84                         get {
  85                                 return data_source;
  86                         }
  87                 }
  88
  89                 public bool IsBinding {
  90                         get {
  91                                 if (control == null || !control.Created)
  92                                         return false;
  93                                 if (manager == null || manager.IsSuspended)
  94                                         return false;
  95                                 return true;
  96                         }
  97                 }
  98
  99                 [DefaultValue ("")]
 100                 public string PropertyName {
 101                         get {
 102                                 return property_name;
 103                         }
 104                 }
 105                 #endregion      // Public Instance Properties
 106
 107                 #region Protected Instance Methods
 108                 protected virtual void OnFormat (ConvertEventArgs cevent)
 109                 {
 110                         if (Format!=null)
 111                                 Format (this, cevent);
 112                 }
 113
 114                 protected virtual void OnParse (ConvertEventArgs cevent)
 115                 {
 116                         if (Parse!=null)
 117                                 Parse (this, cevent);
 118                 }
 119                 #endregion      // Protected Instance Methods
 120
 121
 122                 internal void SetControl (Control control)
 123                 {
 124                         if (control == this.control)
 125                                 return;
 126
 127                         control_property = TypeDescriptor.GetProperties (control).Find (property_name, true);
 128
 129                         if (control_property == null)
 130                                 throw new ArgumentException (String.Concat ("Cannot bind to property '", property_name, "' on target control."));
 131                         if (control_property.IsReadOnly)
 132                                 throw new ArgumentException (String.Concat ("Cannot bind to property '", property_name, "' because it is read only."));
 133
 134                         data_type = control_property.PropertyType; // Getting the PropertyType is kinda slow and it should never change, so it is cached
 135                         control.Validating += new CancelEventHandler (ControlValidatingHandler);
 136
 137                         this.control = control;
 138                         control.DataBindings.Add (this);
 139                 }
 140
 141                 internal void Check (BindingContext binding_context)
 142                 {
 143                         if (control == null || control.BindingContext == null)
 144                                 return;
 145
 146                         manager = control.BindingContext [data_source, data_member];
 147
 148                         manager.AddBinding (this);
 149                         manager.PositionChanged += new EventHandler (PositionChangedHandler);
 150                         manager.CurrentChanged += new EventHandler (CurrentChangedHandler);
 151
 152                         is_null_desc = TypeDescriptor.GetProperties (manager.Current).Find (property_name + "IsNull", false);
 153
 154                         PushData ();
 155                 }
 156
 157                 internal void PullData ()
 158                 {
 159                         if (IsBinding == false || manager.Current == null)
 160                                 return;
 161
 162                         data = control_property.GetValue (control);
 163                         SetPropertyValue (data);
 164                 }
 165
 166                 internal void PushData ()
 167                 {
 168                         if (manager == null || manager.IsSuspended || manager.Current == null)
 169                                 return;
 170
 171                         if (is_null_desc != null) {
 172                                 bool is_null = (bool) is_null_desc.GetValue (manager.Current);
 173                                 if (is_null) {
 174                                         data = Convert.DBNull;
 175                                         return;
 176                                 }
 177                         }
 178
 179                         PropertyDescriptor pd = TypeDescriptor.GetProperties (manager.Current).Find (binding_member_info.BindingField, true);
 180                         if (pd == null) {
 181                                 data = ParseData (manager.Current, manager.Current.GetType ());
 182                         } else {
 183                                 data = ParseData (pd.GetValue (manager.Current), pd.PropertyType);
 184                         }
 185
 186                         data = FormatData (data);
 187                         SetControlValue (data);
 188                 }
 189
 190                 internal void UpdateIsBinding ()
 191                 {
 192                         PushData ();
 193                 }
 194
 195                 private void SetControlValue (object data)
 196                 {
 197                         control_property.SetValue (control, data);
 198                 }
 199
 200                 private void SetPropertyValue (object data)
 201                 {
 202                         PropertyDescriptor pd = TypeDescriptor.GetProperties (manager.Current).Find (binding_member_info.BindingField, true);
 203                         if (pd.IsReadOnly)
 204                                 return;
 205                         data = ParseData (data, pd.PropertyType);
 206                         pd.SetValue (manager.Current, data);
 207                 }
 208
 209                 private void CurrentChangedHandler (object sender, EventArgs e)
 210                 {
 211                         PushData ();
 212                 }
 213
 214                 private void ControlValidatingHandler (object sender, CancelEventArgs e)
 215                 {
 216                         object old_data = data;
 217
 218                         // If the data doesn't seem to be valid (it can't be converted,
 219                         // is the wrong type, etc, we reset to the old data value.
 220                         try {
 221                                 PullData ();
 222                         } catch {
 223                                 data = old_data;
 224                                 SetControlValue (data);
 225                         }
 226                 }
 227
 228                 private void PositionChangedHandler (object sender, EventArgs e)
 229                 {
 230                         PushData ();
 231                 }
 232
 233                 private object ParseData (object data, Type data_type)
 234                 {
 235                         ConvertEventArgs e = new ConvertEventArgs (data, data_type);
 236
 237                         OnParse (e);
 238                         if (data_type.IsInstanceOfType (e.Value))
 239                                 return e.Value;
 240                         if (e.Value == Convert.DBNull)
 241                                 return e.Value;
 242
 243                         return ConvertData (e.Value, data_type);
 244                 }
 245
 246                 private object FormatData (object data)
 247                 {
 248                         if (data_type == typeof (object))
 249                                 return data;
 250
 251                         ConvertEventArgs e = new ConvertEventArgs (data, data_type);
 252
 253                         OnFormat (e);
 254                         if (data_type.IsInstanceOfType (e.Value))
 255                                 return e.Value;
 256
 257                         return ConvertData (data, data_type);
 258                 }
 259
 260                 private object ConvertData (object data, Type data_type)
 261                 {
 262                         TypeConverter converter = TypeDescriptor.GetConverter (data.GetType ());
 263                         if (converter != null && converter.CanConvertTo (data_type))
 264                                 return converter.ConvertTo (data, data_type);
 265
 266                         if (data is IConvertible) {
 267                                 object res = Convert.ChangeType (data, data_type);
 268                                 if (data_type.IsInstanceOfType (res))
 269                                         return res;
 270                         }
 271
 272                         return null;
 273                 }
 274
 275                 #region Events
 276                 public event ConvertEventHandler Format;
 277                 public event ConvertEventHandler Parse;
 278                 #endregion      // Events
 279         }
 280 }