Answer.

In Visual Basic, method overloading allows creating multiple methods with the same name, but with different parameters (types, counts, orders). The keyword Overloads is used before the method declaration for overloading. This helps to make the class interface more flexible and convenient, allowing the same method to be used with different sets of parameters. Overriding, on the other hand, is related to inheritance and allows a derived class to change the implementation of a base class method; for this, the keywords Overrides (in the derived class) and Overridable (in the base class) are used.

Example of method overloading:

Class MathUtil
    ' Overload for the sum of two integers
    Public Overloads Function Add(a As Integer, b As Integer) As Integer
        Return a + b
    End Function
    
    ' Overload for the sum of three integers
    Public Overloads Function Add(a As Integer, b As Integer, c As Integer) As Integer
        Return a + b + c
    End Function
    
    ' Overload for the sum of two floating-point numbers
    Public Overloads Function Add(a As Double, b As Double) As Double
        Return a + b
    End Function
End Class

Trick question

Question: "Can procedures and functions be overloaded by return type? Why?"

Answer: No, in Visual Basic, method overloading is only allowed based on the parameter set (type, count, order). Overloading by return type is not possible: if the method signatures differ only by the result type, a compilation error will occur.

Example:

' This will cause a compilation error!
Overloads Function Foo(x As Integer) As Integer
End Function

Overloads Function Foo(x As Integer) As String
End Function

Examples of real errors due to ignorance of topic subtleties.

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Story

In an internet banking project, a developer implemented user validation methods through overloading, but chose to differ only by return type (for example, one returned Boolean, the other String for the error message). This led to ambiguity in calling the method, inability to compile, and the team had to urgently fix the interface, delaying the release.

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Story

In a corporate inventory system, they tried to create an overloaded method AddItem, differing them by return type (for example, one — result of addition, second — ID of the added record). After integration with an external API, the tests stopped compiling, as the language does not support such overloading, and it was necessary to completely rethink the interaction architecture.

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Story

In an old project for processing scientific data, they tried to overload one function by return type (one Double, the other Decimal). The instance calls turned out to be indistinguishable for the compiler, which led to unexpected runtime errors and double work to fix the library interface.

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