Best way to switch behavior based on type

c#, polymorphism

Solution

There's another possibility. Use virtual dispatch:

class Widget
{
    public virtual void GuiStuff() { }
} 
class RedWidget : Widget
{
    public override void GuiStuff()
    {
        //... red-specific GUI stuff
        base.GuiStuff();
    }
} 
class BlueWidget : Widget
{
    public override void GuiStuff()
    {
        //... blue-specific GUI stuff
        base.GuiStuff();
    }
}

Problem

Possible Duplicate: C# - Is there a better alternative than this to ‘switch on type’? Consider the classic: ``` class Widget { } class RedWidget : Widget { } class BlueWidget : Widget { } ``` For the most part, in my UI, I can treat all `Widget`s the same. However, there are minor differences, which I need to `if` or `switch` through. Possible approaches: Enum Indicator - set by constructor ``` enum WidgetVariety { Red, Blue } class Widget { public WidgetVariety Variety { get; protected set; } } class RedWidget : Widget { public RedWidget() { Variety = Red; } } // Likewise for BlueWidget... switch (mywidget.Variety) { case WidgetVariety.Red: // Red specific GUI stuff case WidgetVariety.Blue: // Blue specific GUI stuff } ``` Use `is` ``` Widget w = ...; if (w is RedWidget) { (RedWidget)w ... } else if (w is BlueWidget) { (BlueWidget)w ... } ``` The reason I've resorted to this is 1) Most of the code is already somewhat written this way, but much uglier. 2) 90% of the code is identical - basically just one column in a GridView needs to be handled differently depending on the type. Which would you recommend? (Or anyone have a better solution?) Edit I know I'll probably be recommended to the Visitor Pattern, but that simply seems to complicated for sparse, minor differences in this case. Edit 2 So one particular difference I was having a hard time sorting out is this column that is different between the two types. In one case, it retrieves a `bool` value, and assigns that to the grid cell. In the other case, it gets a string value. I suppose in this case, it should be obvious that I could define: ``` public object virtual GetColumn4Data(); public override GetColumn4Data() { return m_boolval; } public override GetColumn4Data() { return m_mystring; } ``` This felt wrong to me initially, due to the use of `object`. However, that is the type of the property that I am assigning to in the cell, so of course this makes sense! Too long at the office today it seems...

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