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Friday, September 20, 2013

VB .NET Basics: Input and Output

Sup people!

In today's article we're going to take a look at Visual Basic .NET (VB .NET for short, or even just VB if you're lazy). Like C#, VB .NET is based on the .NET framework, and so many classes and methods will be familiar. The syntax of the language, however, is quite different. Let's get our hands dirty and see for ourselves.

Fire up SharpDevelop (or Visual Studio, if you prefer). From the File menu, go to New -> Solution... so that you get the New Project dialog:


You'll need to open up the "VB" node in the Categories treeview to the left, select "Windows Applications", and then choose the "Console Application" template in the panel to the right. Select a name for the project, choose where on your filesystem to place it, and you're good to go. Hit the "Create" button.

You get the following code in SharpDevelop by default:

Module Program
    Sub Main()
        Console.WriteLine("Hello World!")
       
        ' TODO: Implement Functionality Here
       
        Console.Write("Press any key to continue . . . ")
        Console.ReadKey(True)
    End Sub
End Module

This is no different in functionality from what we saw in my first article here, C# Basics: Input and Output. Here's some example output:


Let's change code to achieve functionality similar to what we had in that article:

Module Program
    Sub Main()
        Console.WriteLine("What is your name?")
        Dim name As String = Console.ReadLine()
        Console.WriteLine("Hello {0}!", name)
        Console.ReadKey(True)
    End Sub
End Module

There are a few things to notice here. The Console methods are exactly the same as in C#, and even support the same {0}-style formatting. The general syntax, however, is very different:

  • There are no semicolons to end statements in VB .NET.
  • Variable declarations begin with the Dim keyword. Its etymology is pretty irrelevant - it's just an ugly way of saying "This here is a variable". Variable types, if included, go after the variable name.
  • Many blocks that are enclosed in braces ({ and }) in C# need an End statement in VB .NET instead (as you can see above). The same goes for things like If statements.
  • Module is like a class - in fact it's the equivalent of a static class. If you don't know what that means, don't worry about it.
  • In VB .NET, functions (also known as methods) come in two flavours. A Function is a regular function that returns some value. A Sub, on the other hand, is a subroutine that doesn't return a value (equivalent to void functions in C/C#/Java, or procedures in Pascal).
When it comes to variable declarations, you can actually leave out the data type, like this:

Dim name = Console.ReadLine()

That's perfectly valid, and name is automatically declared as a String since the type is deduced from the assignment. You can also declare just the variable name:

Dim money

However the type you want to use can't be deduced in this case, and is defaulted to Object.

I consider both of the above examples to be somewhat bad practice - I prefer to always include the variable type as it helps whoever's reading the code understand how that variable should be used. While there are legitimate reasons why you might want to leave it out, most of the time it's not a good idea (a very similar debate revolves around C#'s var keyword for the same reasons).

An important thing to note is that in many cases, VB .NET uses different keywords for data types. For example, you'd declare an integer like this:

Dim age As Integer

...and you declare your typical DateTime like this:

Dim dateOfBirth As Date

Woohoo! :) In this article, we've written our first VB .NET program, and taken a look at basic console input/output as well as dealing with variables.

Personally I don't like VB .NET much because its overuse of keywords, as well as their oddness (see Dim above) makes it a pretty ugly language to use if you're used to using languages with C-style syntax. However, you don't always get to choose which languages to use. So whether you're learning VB .NET as a first language or are switching over from C#, I hope you found this article useful! :) Be sure to check back here for more.

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