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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

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
is it a question of log
Commplementary angles
Idrissa Reply
im all ears I need to learn
right! what he said ⤴⤴⤴
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Ti dsp/bios lab. OpenStax CNX. Sep 03, 2013 Download for free at http://cnx.org/content/col11265/1.8
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