Design

Implementierung

public abstract class Command
{
    public abstract void Execute();

    public abstract void Undo();

    public abstract void Redo();
}

public class CommandManager
{
    #region Static Attributes

    private static object _lockObject = new object();
    private static CommandManager _instance = null;

    #endregion Static Attributes

    #region Attributes

    private Stack<Command> _commandStack = new Stack<Command>();
    private Stack<Command> _undoneStack = new Stack<Command>();

    #endregion Attributes

    #region ctor

    private CommandManager() { }

    #endregion ctor

    #region Static Methods

    public static CommandManager GetInstance
    {
        get
        {
            if (_instance == null)
            {
                lock (_lockObject)
                {
                    _instance = new CommandManager();
                }
            }
            return _instance;
        }
    }

    #endregion Static Methods

    #region Public Methods

    public void Execute(Command command)
    {
        command.Execute();
        _commandStack.Push(command);
    }

    public void Redo()
    {
        Command redoCommand = _undoneStack.Pop();
        redoCommand.Redo();
        _commandStack.Push(redoCommand);
    }

    public void Undo()
    {
        Command undoCommand = _commandStack.Pop();
        undoCommand.Undo();
        _undoneStack.Push(undoCommand);
    }

    #endregion Public Methods
}

public class Person : ICloneable
{
    #region Properties

    public String Firstname { get; set; }
    public String Lastname { get; set; }

    #endregion Properties

    #region ICloneable Members

    public object Clone()
    {
        Person p = new Person();
        p.Firstname = this.Firstname;
        p.Lastname = this.Lastname;
        return p;
    }

    #endregion ICloneable Members

    #region Overrides

    public override string ToString()
    {
        return String.Format("{0}, {1}", Lastname, Firstname);
    }

    #endregion Overrides
}

public class PersonCommand : Command
{
    private Person _person;
    private Person _personStateBefore;

    public PersonCommand(Person person)
    {
        _person = person;
    }

    public override void Execute()
    {
        _personStateBefore = _person.Clone() as Person;

        _person.Firstname = "Norbert";
        _person.Lastname = "Eder";
    }

    public override void Undo()
    {
        _person.Firstname = _personStateBefore.Firstname;
        _person.Lastname = _personStateBefore.Lastname;
    }

    public override void Redo()
    {
        Execute();
    }
}

CommandManager manager = CommandManager.GetInstance;

Person p = new Person();
p.Firstname = "<not set>";
p.Lastname = "<not set>";
Console.WriteLine(
    String.Format("Before first execution: " + p.ToString()));

manager.Execute(new PersonCommand(p));
Console.WriteLine(
    String.Format("After first execution : " + p.ToString()));

manager.Undo();
Console.WriteLine(
    String.Format("After undo            : " + p.ToString()));

manager.Redo();
Console.WriteLine(
    String.Format("After redo            : " + p.ToString()));

Console.Read();

Fazit

Design Patterns

Windows Presentation Foundation

Windows Forms

Sonstiges

public System.Drawing.Image Convert(
  FrameworkElement controlToRender)
{
    RenderTargetBitmap rtb = new RenderTargetBitmap(
      (int)controlToRender.ActualWidth, 
      (int)controlToRender.ActualHeight, 
      90, 
      90, 
      PixelFormats.Default);
    
    Visual vis = (Visual)controlToRender;
    rtb.Render(vis);
    
    System.Windows.Controls.Image img = 
      new System.Windows.Controls.Image();
    img.Source = rtb;
    img.Stretch = Stretch.None;
    img.Measure(new System.Windows.Size(
      (int)controlToRender.ActualWidth, 
      (int)controlToRender.ActualHeight));
    System.Windows.Size sizeImage = img.DesiredSize;
    img.Arrange(new System.Windows.Rect(new 
      System.Windows.Point(0, 0), sizeImage));
    
    RenderTargetBitmap rtb2 = new RenderTargetBitmap(
      (int)rtb.Width, 
      (int)rtb.Height, 
      90, 
      90, 
      PixelFormats.Default);
    rtb2.Render(img);
    
    PngBitmapEncoder png = new PngBitmapEncoder();
    png.Frames.Add(BitmapFrame.Create(rtb2));
    
    Stream ms = new MemoryStream();
    png.Save(ms);
    
    ms.Position = 0;
    
    System.Drawing.Image retImg = 
      System.Drawing.Image.FromStream(ms);
    return retImg;
}

• BmpBitmapEncoder
• GifBitmapEncoder
• JpegBitmapEncoder
• PngBitmapEncodery
• TiffBitmapEncoder
• WmpBitmapEncoder

Hintergrund

object propertyValue = this.PropertyValue;
object obj3 = this.UITypeEditor.EditValue
    (this, this, propertyValue);
if (!this.Disposed)
{
    if ((obj3 != propertyValue) 
        && this.IsValueEditable)
    {
        iva.CommitValue(this, obj3);
    }
    if (this.InternalExpanded)
    {
        PropertyGridView.GridPositionData data = 
          this.GridEntryHost.CaptureGridPositionData();
        this.InternalExpanded = false;
        this.RecreateChildren();
        data.Restore(this.GridEntryHost);
    }
    else
    {
        this.RecreateChildren();
    }
}

Mögliche Workarounds

public class CustomCollectionEditor : UITypeEditor
{
    private CollectionEditor _editor = 
      new CollectionEditor(typeof(CustomCollection));
    
    public override object EditValue(
      ITypeDescriptorContext context, 
      IServiceProvider provider, 
      object value)
    {
        if (value != null)
        {
            value = this._editor.EditValue(context, provider, value);
            CustomCollection list = (CustomCollection)value;
            return list.Clone();
        }

        return base.EditValue(context, provider, value);
    }

    public override UITypeEditorEditStyle GetEditStyle(
      ITypeDescriptorContext context)
    {
        return this._editor.GetEditStyle(context);
    } 
}

private CustomCollection _collection = new CustomCollection();

[TypeConverter(typeof(CustomCollection))]
[Editor(typeof(CustomCollectionEditor), typeof(UITypeEditor))]
public CustomCollection MyCollection
{
  get { return this._collection; }
  set { this._collection = value; }
}

Fazit

.NET Base Framework

Windows Presentation Foundation

Visual Studio

List<int> testList = new List<int>();

for (int i = 0; i < 100; i++)
    testList.Add(i);

int sum = 0;

testList.ForEach(delegate(int val)
{
    sum += val;
});

Console.WriteLine(sum.ToString());