I drag in the panel , but no rectangle appear 
VB.NET:
Dim MyPoint As ArrayList = New ArrayList
Dim DragFlag As Boolean = False
Dim StartPt, EndPt, FalseStartPt, FalseEndPt As PointF
Dim myshapetype As ArrayList = New ArrayList
Dim centreX As Integer = 448 / 2
Dim centreY As Integer = 228 / 2
Dim curstatus As String = "draw"
Dim TrueX, TrueY
Private Sub panel1_Mousedown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Panel1.MouseDown
'If curstatus = "Move" Or curstatus = "ZoomRegion" Then
' DragFlag = True
'End If
TrueX = (e.X - Panel1.Width / 2) * Width / Panel1.Width + centreX
TrueY = (e.Y - Panel1.Height / 2) * Height / Panel1.Height + centreY
StartPt = New PointF(TrueX, TrueY)
EndPt = New PointF(TrueX, TrueY)
FalseStartPt = New PointF(e.X, e.Y) 'coordinate after zoomming in or out
FalseEndPt = New PointF(e.X, e.Y)
If curstatus = "Draw" Then
DragFlag = True
MyPoint.Add(New PointF(TrueX, TrueY))
ElseIf curstatus = "ZoomIn" Then
TrueX = centreX
TrueY = centreY
Width = Width * Width / Panel1.Width
Height = Height * Height / Panel1.Height
Panel1.Invalidate()
End If
End Sub
Private Sub panel1_Mousemove(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Panel1.MouseMove
'If curstatus = "Move" Or curstatus = "ZoomRegion" Then
' Panel1.Invalidate()
'End If
Label1.Text = "X:" & e.X & "Y:" & e.Y
TrueX = (e.X - Panel1.Width / 2) * Width / Panel1.Width + centreX
TrueY = (e.Y - Panel1.Height / 2) * Height / Panel1.Height + centreY
If DragFlag Then
EndPt = New PointF(TrueX, TrueY)
FalseEndPt = New PointF(e.X, e.Y)
If curstatus = "Draw" Then
Panel1.Invalidate()
End If
End If
End Sub
Private Sub panel1_Mouseup(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Panel1.MouseUp
'If curstatus = "Move" Then
' DragFlag = False
' centreX = -TrueX * Width / Panel1.Width + centreX
' centreY = -TrueY * Height / Panel1.Height + centreY
' Panel1.Invalidate()
'End If
'If curstatus = "ZoomRegion" Then
' DragFlag = False
' Dim w, h
' w = Math.Abs(FalseEndPt.X - FalseStartPt.X)
' h = Math.Abs(FalseEndPt.Y - FalseStartPt.Y)
' If w > 0 And h > 0 Then
' Dim TempX, TempY, Ratio
' TempX = (FalseStartPt.X + FalseEndPt.X) / 2
' TempY = (FalseStartPt.Y + FalseEndPt.Y) / 2
' centreX = (TempX - Panel1.Width / 2) * Width / Panel1.Width + centreX
' centreY = (TempY - Panel1.Height / 2) * Height / Panel1.Height + centreY
' If w > h Then
' Ratio = Width / Panel1.Width
' Else
' Ratio = Height / Panel1.Height
' End If
' Width = w * Ratio : Height = h * Ratio
' Panel1.Invalidate()
' End If
'End If
Label1.Text = "X:" & e.X & "Y:" & e.Y
TrueX = (e.X - Panel1.Width / 2) * Width / Panel1.Width + centreX
TrueY = (e.Y - Panel1.Height / 2) * Height / Panel1.Height + centreY
EndPt = New PointF(TrueX, TrueY)
FalseEndPt = New PointF(e.X, e.Y)
If curstatus = "Draw" Then
DragFlag = False
MyPoint.Add(New PointF(TrueX, TrueY))
myshapetype.Add("Rectangle")
End If
Panel1.Invalidate()
End Sub
Private Sub Panel1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Panel1.Paint
Dim g As Graphics = e.Graphics
Dim i As Integer
Dim mypen As New Pen(Color.DarkBlue)
'If curstatus = "ZoomRegion" And DragFlag Then
' DrawRectangle(g, FalseStartPt, FalseEndPt, mypen)
'End If
g.TranslateTransform(-centreX, -centreY, System.Drawing.Drawing2D.MatrixOrder.Prepend)
g.ScaleTransform(Panel1.Width / Width, Panel1.Width / Width, System.Drawing.Drawing2D.MatrixOrder.Append)
g.TranslateTransform(Panel1.Width / 2, Panel1.Height / 2, System.Drawing.Drawing2D.MatrixOrder.Append)
For i = 0 To MyPoint.Count Step 2
If i + 1 < MyPoint.Count Then
Dim TempStartPt As PointF = MyPoint(i)
Dim TempEndPt As PointF = MyPoint(i + 1)
DrawRectangle(g, TempStartPt, TempEndPt, mypen)
End If
Next
If curstatus = "Draw" And DragFlag = True Then
DrawRectangle(g, StartPt, EndPt, mypen)
End If
End Sub
Private Sub MenuItem1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MenuItem1.Click
shape.Text = "Rectangle"
shape.ImageIndex = 4
End Sub
Private Sub MenuItem2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MenuItem2.Click
shape.Text = "Ellipse"
shape.ImageIndex = 0
End Sub
Private Sub MenuItem3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MenuItem3.Click
shape.Text = "Line"
shape.ImageIndex = 1
End Sub
Sub DrawRectangle(ByVal g As Graphics, ByVal sPt As PointF, ByVal ePt As PointF, ByVal pen As Pen)
Dim minX, minY, maxX, maxY
If sPt.X > ePt.X Then
If maxX - minX > 0 And maxY - minY > 0 Then
g.DrawRectangle(pen, minX, minY, maxX - minX, maxY - minY)
End If
End If
End Sub
End Class
