WriteOnly Property or Method?

I think a property indicates something that can be read-only or read/write. The behaviour of a write-only property is not obvious so I avoid creating them.

As an example, setting a list of values in a drop-down on a view and accessing the selected item:

public interface IWidgetSelector
{
  void SetAvailableWidgets(string[] widgets);

  string SelectedWidget { get; set; }
}

Makes more sense than:

public interface IWidgetSelector
{
  string[] AvailableWidgets { set; }

  string SelectedWidget { get; set; }
}

For what it's worth, the Microsoft Framework Design Guidelines (as embodied in their FxCop tool) discourage Write-Only Properties and flag their presence as an API design issue, due to the unintuitiveness of that approach.

Here is an example of code I have used in an XNA project. As you can see, Scale is write-only, it is useful and (reasonably) intuitive and a read property (get) would not make sense for it. Sure it could be replaced with a method, but I like the syntax.

public class MyGraphicalObject
      {
      public double ScaleX { get; set; }
      public double ScaleY { get; set; }
      public double ScaleZ { get; set; }

      public double Scale { set { ScaleX = ScaleY = ScaleZ = value; } }

      // more...
      }