Answer.

In Visual Basic, procedural programming allows for clear structuring of code through the reuse of subprograms (Sub, Function) to minimize duplication and enhance readability.

Background

Initially, programming in VB evolved around working with large blocks of code within forms and modules. This led to logic duplication and complicated debugging. The separation into procedures and functions represented a shift towards a more modular architecture.

Problem

Poorly structured applications contain identical code in different places, making maintenance, debugging, and reusability challenging.

Solution

Using procedures (Sub) and functions (Function) with arguments and return values. A good practice is to extract recurring logic into separate methods, adhering to the DRY principle (Don't Repeat Yourself).

Code Example:

' Handler calling the reusable function
Sub btnCalculate_Click(sender As Object, e As EventArgs)
    Dim result As Double = CalculateDiscount(100, 0.2)
    MessageBox.Show($"Discount: {result}")
End Sub

' Reusable function
Function CalculateDiscount(total As Double, rate As Double) As Double
    Return total * (1 - rate)
End Function

Key Features:

• Code reuse through common methods and functions.
• Simplicity of further code maintenance.
• Clear decomposition of logic.

Tricky Questions.

Can procedures and functions in Visual Basic be declared with the same name if they differ only by their return types?

In Visual Basic, a procedure or function name must be unique within its scope, and overloading solely by the return type is not possible. Overloading is only supported by parameter signatures.

Code Example:

' INCORRECT — compilation error
Function GetValue() As Integer
    Return 1
End Function

Function GetValue() As String
    Return "Test"
End Function

If a parameter is declared as Optional, is it mandatory to specify a default value?

Yes, it is necessary to provide a default value for Optional parameters.

Code Example:

Function Sum(a As Integer, Optional b As Integer = 0) As Integer
    Return a + b
End Function

Can Exit Sub/Exit Function be used to exit not only from the current procedure but also from parent ones?

No, Exit Sub/Exit Function exits only from the current procedure. To control the flow at the external procedure level, flow control structures like If/Return or exception handling should be used.

Common Mistakes and Anti-patterns

• Duplicating business logic instead of extracting it into separate methods.
• Using procedures with a large number of parameters and poor readability.
• Incorrectly using global variables to share data between procedures.

Real-life Example

Negative Case

In a project, the discount calculation is implemented as separate code snippets in several event handlers across different forms. When changing the formula, the code needs to be manually corrected in all places.

Pros:

• Quick results during prototyping.

Cons:

• Difficult to maintain.
• Risk of errors during modifications.
• More code to support.

Positive Case

Extracting the discount calculation into a separate function CalculateDiscount and using it in all necessary places through calls.

Pros:

• Easy to make changes in one place.
• Less likelihood of errors.
• Improved readability and testability.

Cons:

• Time required for decomposition and structuring of code.