.net3.0 extension methods for interface

.net得扩展方法用在接口上，能使得用户不需要实现，额外获得一些方法：

 publicinterfaceICollectionControlVisualInformationHelper

 

{

int VisualIndexofCurrentItem(Control targetControl, ICollectionView view);

int CountOfVisualItems(Control targetControl, ICollectionView view);

int VisualIndexConvertToDataItemIndex(int visualIndex);

void DoSomethingAfterMoveUpDown(Control targetControl, ICollectionView view);

}

 

internalstaticclassICollectionControlVisualInformationHelperExtensionMethod

{

publicstaticint VisualIndexOfPreviousItem(thisICollectionControlVisualInformationHelper helper,Control targetControl, ICollectionView view)

{

return helper.VisualIndexConvertToDataItemIndex(helper.VisualIndexofCurrentItem(targetControl,view) - 1);

}

publicstaticint VisualIndexOfNextItem(thisICollectionControlVisualInformationHelper helper, Control targetControl, ICollectionView view)

{

return helper.VisualIndexConvertToDataItemIndex(helper.VisualIndexofCurrentItem(targetControl, view) + 1);

}

}

这样使得用户实现4个方法，却获得了接口的六个方法。