You may have heard of VB11, currently in the VS11 developer preview. It adds two main syntax elements - Iterator functions and Async methods. I don't know much about Async methods yet, but here's a quick Iterator tutorial.
Basically, you put the Iterator keyword before the Function keyword and it becomes an iterator and returns an IEnumerable(Of t). Then, you have some kind of loop, and use the new Yield keyword to "return" a value. For example, this method generates lines from an array of points:
Here's how you might use it:Code:''' <summary>
''' Represents a line.
''' </summary>
Private Structure Line
Public Start As Point
Public [End] As Point
Public Function IsVertical() As Boolean
Return Me.Start.X = Me.End.X
End Function
Public Function IsHorizontal() As Boolean
Return Me.Start.Y = Me.End.Y
End Function
Public Function IsEmpty() As Boolean
Return Me.IsHorizontal() AndAlso Me.IsVertical()
End Function
Public Shared Operator =(ByVal a As Line, ByVal b As Line) As Boolean
Return a.Start = b.Start AndAlso a.End = b.End
End Operator
Public Shared Operator <>(ByVal a As Line, ByVal b As Line) As Boolean
Return a.Start <> b.Start OrElse a.End <> b.End
End Operator
End Structure
''' <summary>
''' Gets the lines between each point.
''' </summary>
''' <param name="points">The points for which to create lines.</param>
Private Shared Iterator Function Lines(ByVal points As IEnumerable(Of Point)) As IEnumerable(Of Line)
Dim last As Point?
For Each p As Point In points
If last IsNot Nothing Then Yield New Line With {
.Start = last.Value,
.End = p
}
last = p
Next
End Function
Use iterators well - they can be really great sometimes.Code:' Draw a square in a *very* roundabout way :)
' By the way, you can omit types in For Each statements in VB 11:
' v
For Each line In Lines({
Point.Empty,
New Point(100, 0),
New Point(100, 100),
New Point(0, 100),
Point.Empty
})
myGraphics.DrawLine(Pens.Red, line.Start, line.End)
Next
