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

   1 // Permission is hereby granted, free of charge, to any person obtaining
   2 // a copy of this software and associated documentation files (the
   3 // "Software"), to deal in the Software without restriction, including
   4 // without limitation the rights to use, copy, modify, merge, publish,
   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
  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 object data;
  47                 private Type data_type;
  48
  49                 #region Public Constructors
  50                 public Binding (string propertyName, object dataSource, string dataMember)
  51                 {
  52                         property_name = propertyName;
  53                         data_source = dataSource;
  54                         data_member = dataMember;
  55                         binding_member_info = new BindingMemberInfo (dataMember);
  56                 }
  57                 #endregion      // Public Constructors
  58
  59                 #region Public Instance Properties
  60                 public BindingManagerBase BindingManagerBase {
  61                         get {
  62                                 return manager;
  63                         }
  64                 }
  65
  66                 public BindingMemberInfo BindingMemberInfo {
  67                         get {
  68                                 return binding_member_info;
  69                         }
  70                 }
  71
  72                 [DefaultValue (null)]
  73                 public Control Control {
  74                         get {
  75                                 return control;
  76                         }
  77                 }
  78
  79                 public object DataSource {
  80                         get {
  81                                 return data_source;
  82                         }
  83                 }
  84
  85                 public bool IsBinding {
  86                         get {
  87                                 if (control == null || !control.Created)
  88                                         return false;
  89                                 if (manager == null || manager.IsSuspended)
  90                                         return false;
  91                                 return true;
  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                         control_property = TypeDescriptor.GetProperties (control).Find (property_name, true);
 124
 125                         if (control_property == null)
 126                                 throw new ArgumentException (String.Concat ("Cannot bind to property '", property_name, "' on target control."));
 127                         if (control_property.IsReadOnly)
 128                                 throw new ArgumentException (String.Concat ("Cannot bind to property '", property_name, "' because it is read only."));
 129
 130                         data_type = control_property.PropertyType; // Getting the PropertyType is kinda slow and it should never change, so it is cached
 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 || control.BindingContext == null)
 139                                 return;
 140
 141                         manager = control.BindingContext [data_source, data_member];
 142
 143                         manager.AddBinding (this);
 144                         manager.PositionChanged += new EventHandler (PositionChangedHandler);
 145
 146                         is_null_desc = TypeDescriptor.GetProperties (manager.Current).Find (property_name + "IsNull", false);
 147
 148                         PushData ();
 149                 }
 150
 151                 internal void PullData ()
 152                 {
 153                         if (IsBinding == false || manager.Current == null)
 154                                 return;
 155
 156                         data = control_property.GetValue (control);
 157                         SetPropertyValue (data);
 158                 }
 159
 160                 internal void PushData ()
 161                 {
 162                         if (manager == null || manager.IsSuspended || manager.Current == null)
 163                                 return;
 164
 165                         if (is_null_desc != null) {
 166                                 bool is_null = (bool) is_null_desc.GetValue (manager.Current);
 167                                 if (is_null) {
 168                                         data = Convert.DBNull;
 169                                         return;
 170                                 }
 171                         }
 172
 173                         PropertyDescriptor pd = TypeDescriptor.GetProperties (manager.Current).Find (binding_member_info.BindingField, true);
 174                         if (pd == null) {
 175                                 data = manager.Current;
 176                         } else {
 177                                 data = pd.GetValue (manager.Current);
 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                         control_property.SetValue (control, data);
 192                 }
 193
 194                 private void SetPropertyValue (object data)
 195                 {
 196                         PropertyDescriptor pd = TypeDescriptor.GetProperties (manager.Current).Find (binding_member_info.BindingField, true);
 197                         if (pd.IsReadOnly)
 198                                 return;
 199                         data = ParseData (data, pd.PropertyType);
 200                         pd.SetValue (manager.Current, data);
 201                 }
 202
 203                 private void ControlValidatingHandler (object sender, CancelEventArgs e)
 204                 {
 205                         object old_data = data;
 206
 207                         // If the data doesn't seem to be valid (it can't be converted,
 208                         // is the wrong type, etc, we reset to the old data value.
 209                         try {
 210                                 PullData ();
 211                         } catch {
 212                                 data = old_data;
 213                                 SetControlValue (data);
 214                         }
 215                 }
 216
 217                 private void PositionChangedHandler (object sender, EventArgs e)
 218                 {
 219                         PushData ();
 220                 }
 221
 222                 private object ParseData (object data, Type data_type)
 223                 {
 224                         ConvertEventArgs e = new ConvertEventArgs (data, data_type);
 225
 226                         OnParse (e);
 227                         if (data_type.IsInstanceOfType (e.Value))
 228                                 return e.Value;
 229                         if (e.Value == Convert.DBNull)
 230                                 return e.Value;
 231
 232                         return ConvertData (e.Value, data_type);
 233                 }
 234
 235                 private object FormatData (object data)
 236                 {
 237                         if (data_type == typeof (object))
 238                                 return data;
 239
 240                         ConvertEventArgs e = new ConvertEventArgs (data, data_type);
 241
 242                         OnFormat (e);
 243                         if (data_type.IsInstanceOfType (e.Value))
 244                                 return e.Value;
 245
 246                         return ConvertData (data, data_type);
 247                 }
 248
 249                 private object ConvertData (object data, Type data_type)
 250                 {
 251                         TypeConverter converter = TypeDescriptor.GetConverter (data.GetType ());
 252                         if (converter != null && converter.CanConvertTo (data_type))
 253                                 return converter.ConvertTo (data, data_type);
 254
 255                         if (data is IConvertible) {
 256                                 object res = Convert.ChangeType (data, data_type);
 257                                 if (data_type.IsInstanceOfType (res))
 258                                         return res;
 259                         }
 260
 261                         return null;
 262                 }
 263
 264                 #region Events
 265                 public event ConvertEventHandler Format;
 266                 public event ConvertEventHandler Parse;
 267                 #endregion      // Events
 268         }
 269 }