Determining what objects fall within a selection rectangle (marquee) - vb.net

Question

I'm writing a program that (amongst other things) provides an IDE-like environment for the user where they can select one or more objects with a rectangualr selection tool.
All selections will be a simple rectangle, and all selectable objects will be simple rectangles as well.
I already have the code (VB.Net) to create the rubber-banding effect visually - what I need is an efficient algorithm that will tell me what objects have at least a portion of their area within the final selection rectangle.
If it helps to visualize, what I want to do would be identical to dragging a selection box over icons on the Windows desktop... whichever icons have even a portion of their areas located within that selection marquee are highlighted (selected).
Any help would be appreciated... thank you in advance

Answer 1

Dim Rect1 As New Rectangle(10, 10, 20, 20)
Dim Rect2 As New Rectangle(5, 5, 20, 20)
Debug.Print(Rect1.IntersectsWith(Rect2))

Answer 2

IntersectsWith works as BigFunger already has mentioned. But aditionally you should check if a rectangle contains another rectangle(intersectsWith only checks for intersection).
A small sample-form that demonstrates it:
Public Class SelectionRectangle
Private first As Point
Private allRectangles As New List(Of RectangleF)
Private Sub form_MouseDown(ByVal sender As Object, ByVal e As MouseEventArgs) Handles Me.MouseDown
first = New Point(e.X, e.Y)
End Sub
Private Sub form_MouseUp(ByVal sender As Object, ByVal e As MouseEventArgs) Handles Me.MouseUp
Dim p As New Pen(Brushes.Black, 2)
Dim g As Graphics
Dim second As New Point(e.X, e.Y)
Dim x, y, w, h As Int32
x = DirectCast(IIf(first.X > second.X, second.X, first.X), Int32)
y = DirectCast(IIf(first.Y > second.Y, second.Y, first.Y), Int32)
w = Math.Abs(second.X - first.X)
h = Math.Abs(second.Y - first.Y)
Dim nextRec As New RectangleF(x, y, w, h)
Dim intersects As Boolean = False
For Each rec As RectangleF In allRectangles
If rec.Contains(nextRec) OrElse rec.IntersectsWith(nextRec) Then
intersects = True
Exit For
End If
Next
If Not intersects Then
p.DashStyle = System.Drawing.Drawing2D.DashStyle.Dot
g = Me.CreateGraphics()
g.DrawLine(p, first.X, first.Y, second.X, first.Y)
g.DrawLine(p, second.X, second.Y, first.X, second.Y)
g.DrawLine(p, first.X, first.Y, first.X, second.Y)
g.DrawLine(p, second.X, second.Y, second.X, first.Y)
allRectangles.Add(nextRec)
Else
Beep()
End If
End Sub
End Class
UPDATE: changed this code to 1.first check in both directions and 2. and more important for you: checks also if one rectangle not only intersects another but additionally if it contains another.