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The module is a lab assignment to help you better understand the very basics of Microsoft Visual Basic delegates.


This lab module will help you become familiar with the basics of delegates in Microsoft Visual Basic(V). The exercises are written assuming you are using Visual Basic 2005 and the .NET Framework version 2.0 (or later). Some older versions will work the same, but you may need to figure out some differences. It should work with newer version also.

Module prerequisites

You should complete the Visual Basic Threads and Semaphores lab before this one.


Part 1

  • In this part you will make a project with a thread that will try to change a TextBox text without using a delegate method. When the thread tries to change the TextBox text it won't work because the TextBox control is not handled by the thread.
  • Start up Visual Studio and create a new Visual Basic project.
  • On the GUI, put a new TextBox. By default it should have the name TextBox1 .
  • Create a thread called Task1 and start the thread in the Form1_Load method.
  • In the thread method Task1 , assign a string to the TextBox.
  • Run your program and observe what happens. You should get an error when the thread tries to access the TextBox control. Record what the error says.

Part 2

  • In this part we will make a delegate that will allow the thread to change the text in the TextBox.
  • Either start a new project or modify the one from the previous part. What you should have in your project is:
  1. A TextBox on the GUI with the name TextBox1 .
  2. A thread called Task1 that is started in the Form1_Load method.
  • Add commands to define a delegate type and an instance of a delegate. If you want to use the names shown here you can. These statements should be right under the beginning of the Form1 class (right after " Public Class Form1 ").
Delegate Sub DelegateType(ByVal myStr As String) Dim IDel As New DelegateType(AddressOf DelegateMethod)
  • Make a new DelegateMethod method that takes a string as an input and uses it to change the text of the TextBox.
  • In the Task1 method, use the TextBox1 to invoke the delegate method. Have it write the text "Task Text" to the TextBox.
  • Run your program and observe that the text "Task Text" gets written to the TextBox.

Part 3

  • In this part we will make a simple clock. All we will do is continuously get the current time and write it to the TextBox.
  • In this part we will have everything that is in the previous part so you can start where it left off. Your project should have:
  1. A TextBox on the GUI with the name TextBox1 .
  2. A thread that uses the Task1 method that is started in the Form1_Load method.
  3. Commands to define a delegate and an instance of a delegate.
  4. A delegate method that writes the input string to the TextBox.
  • In the thread, we will have it get the current date/time and the write it to the TextBox.
  • Put the following commands that will define objects to get the current date/time.
Dim count As Integer Dim dispDt As DateTimeDim datePatt As String = "M/d/yyyy hh:mm:ss tt" Dim dtString As String
  • In the thread make a continuous while loop that puts the date into the string dtString and then sends that string to the delegate. To get the date use the command:
dispDt = DateTime.Now ' get the time now dtString = dispDt.ToString(datePatt) ' Convert the date to a string
  • In the while loop make the thread sleep for 100 ms so that it is not doing too much processing. It will get the time/date and write it to the TextBox every 100 ms.
  • Run your program and observe that the text displays the date/time and that the seconds change.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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