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VB.net create lines on dragging

Posted on 2014-09-08
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Last Modified: 2014-10-10
Hi

I want to create a form that allows the user to connect different tables columns similar to that
in the image. What code would I use to draw the line when the user drags from one column name to another
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Question by:Murray Brown
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Jacques Bourgeois (James Burger) earned 2000 total points
ID: 40311183
And the image is... where?

I suppose that you want to do what is seen in many Microsoft interfaces (be it Access Relations, SQL Server Diagrams, Visual Studio XML Designers). The basic code to draw the line is quite easy. This is usually done in the Paint event of the Form or the control in which you display your tables:

Dim pen As New Pen(Color.Black)
e.Graphics.DrawLine(pen, x, y, x1, y1)

OnPaint is called whenever the form needs to redraw itself. It is called automatically in some situations, such as when the Form is covered by another one and the user brings it to the forefront. But you can force it to do so by calling Refresh on the Form or control when you detect a Drag.

In there, e.Graphics is passed as a parameter to the Paint method and represents your tool to draw on the Form or control.

x and y are the starting position of your line in pixels, relative to the upper left of the Form or control. x1 and y1 are the ending point of your line.

The hard part is to determine x, y, x1, y1. It depends on how you display your tables on the screen. You usually record x and y on the MouseDown of the starting control, save them in a Point variable at the form level, and reuse them along x1 and y1 on the MouseUp of the destination control.
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Author Comment

by:Murray Brown
ID: 40311514
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Author Comment

by:Murray Brown
ID: 40311517
Hi. Apologies. The image that I just put up is similar to the one I originally wanted to post but can't find now. Essentially it is very similar to the Access query builder
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Author Comment

by:Murray Brown
ID: 40311528
Could you perhaps just tell me what the VB.net code would be to draw one line. Thanks
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Author Closing Comment

by:Murray Brown
ID: 40372379
thanks
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