How to know the width and height in pixels of a given image programmatically

You will have to create a Bitmap instance from the image file and then query the Width and Height as follows:

VB.NET

Dim bm As Bitmap = New Bitmap(Server.MapPath('b2346.jpg'))
Response.Write('Height  :' + bm.Height.ToString())
Response.Write('<br> Width :' + bm.Width.ToString())

C#

Bitmap bm = new Bitmap( Server.MapPath('b2346.jpg'));
Response.Write ('Height  :' + bm.Height.ToString() );
Response.Write ('<br> Width :' +bm.Width.ToString() );