1 using System;

     2 using System.Collections.Generic;

     3 using System.Linq;

     4 using System.Text;

     5 using System.ComponentModel;

     6 using System.Diagnostics;

     7 

     8 namespace FingersDance.ViewModel

     9 {

    10     /// <summary>

    11     /// Base class for all ViewModel classes in the application.

    12     /// It provides support for property change notifications 

    13     /// and has a DisplayName property.  This class is abstract.

    14     /// </summary>

    15     public abstract class ViewModelBase : INotifyPropertyChanged, IDisposable

    16     {

    17         #region Constructor

    18 

    19         protected ViewModelBase()

    20         {

    21         }

    22 

    23         #endregion // Constructor

    24 

    25         #region DisplayName

    26 

    27         /// <summary>

    28         /// Returns the user-friendly name of this object.

    29         /// Child classes can set this property to a new value,

    30         /// or override it to determine the value on-demand.

    31         /// </summary>

    32         public virtual string DisplayName { get; protected set; }

    33 

    34         #endregion // DisplayName

    35 

    36         #region Debugging Aides

    37 

    38         /// <summary>

    39         /// Warns the developer if this object does not have

    40         /// a public property with the specified name. This 

    41         /// method does not exist in a Release build.

    42         /// </summary>

    43         [Conditional("DEBUG")]

    44         [DebuggerStepThrough]

    45         public void VerifyPropertyName(string propertyName)

    46         {

    47             // Verify that the property name matches a real,  

    48             // public, instance property on this object.

    49             if (TypeDescriptor.GetProperties(this)[propertyName] == null)

    50             {

    51                 string msg = "Invalid property name: " + propertyName;

    52 

    53                 if (this.ThrowOnInvalidPropertyName)

    54                     throw new Exception(msg);

    55                 else

    56                     Debug.Fail(msg);

    57             }

    58         }

    59 

    60         /// <summary>

    61         /// Returns whether an exception is thrown, or if a Debug.Fail() is used

    62         /// when an invalid property name is passed to the VerifyPropertyName method.

    63         /// The default value is false, but subclasses used by unit tests might 

    64         /// override this property's getter to return true.

    65         /// </summary>

    66         protected virtual bool ThrowOnInvalidPropertyName { get; private set; }

    67 

    68         #endregion // Debugging Aides

    69 

    70         #region INotifyPropertyChanged Members

    71 

    72         /// <summary>

    73         /// Raised when a property on this object has a new value.

    74         /// </summary>

    75         public event PropertyChangedEventHandler PropertyChanged;

    76 

    77         /// <summary>

    78         /// Raises this object's PropertyChanged event.

    79         /// </summary>

    80         /// <param name="propertyName">The property that has a new value.</param>

    81         protected virtual void OnPropertyChanged(string propertyName)

    82         {

    83             this.VerifyPropertyName(propertyName);

    84 

    85             PropertyChangedEventHandler handler = this.PropertyChanged;

    86             if (handler != null)

    87             {

    88                 var e = new PropertyChangedEventArgs(propertyName);

    89                 handler(this, e);

    90             }

    91         }

    92 

    93         #endregion // INotifyPropertyChanged Members

    94 

    95         #region IDisposable Members

    96 

    97         /// <summary>

    98         /// Invoked when this object is being removed from the application

    99         /// and will be subject to garbage collection.

   100         /// </summary>

   101         public void Dispose()

   102         {

   103             this.OnDispose();

   104         }

   105 

   106         /// <summary>

   107         /// Child classes can override this method to perform 

   108         /// clean-up logic, such as removing event handlers.

   109         /// </summary>

   110         protected virtual void OnDispose()

   111         {

   112         }

   113 

   114 #if DEBUG

   115         /// <summary>

   116         /// Useful for ensuring that ViewModel objects are properly garbage collected.

   117         /// </summary>

   118         ~ViewModelBase()

   119         {

   120             string msg = string.Format("{0} ({1}) ({2}) Finalized", this.GetType().Name, this.DisplayName, this.GetHashCode());

   121             System.Diagnostics.Debug.WriteLine(msg);

   122         }

   123 #endif

   124 

   125         #endregion // IDisposable Member

   126     }

   127 }