VB.NET Shared Function

Use the Shared modifier to specify that a member is not part of a type instance.

Shared. A Shared function is not part of an instance. Some functions and fields may be specific to an entire type, not an instance. The Shared modifier specifies that a function is meant for the entire type, not just a certain instance of it.Function

Example. This program introduces a Widget class. In the Widget class, we see a Public Shared Function and a Public Function. In the Main subroutine, we can call Widget.Test() because Test() is a Shared function. No instance is required.Sub

However: We must instantiate Widget, with New Widget(), to call TestB(). The TestB() function is not Shared.

Note: Fields, such as the _value field above, are also Shared or not Shared.

And: In a program, Shared fields can be accessed by Shared Functions. Regular Functions can access both Shared fields and also regular fields.

Thus: This means that Shared functions have additional restrictions on what they can do.

VB.NET program that uses Shared function Module Module1 Class Widget Public Shared Function Test() As Integer ' Cannot access regular fields. Return Integer.Parse("1") End Function Dim _value As String = "2" Public Function TestB() As Integer ' Can access regular fields. Return Integer.Parse(_value) End Function End Class Sub Main() ' Use Shared Function. Console.WriteLine(Widget.Test()) ' Use Non-Shared Function. Dim w As Widget = New Widget() Console.WriteLine(w.TestB()) End Sub End Module Output 1 2

Performance. The .NET Framework's execution engine needs to evaluate instances before an instance function can be called. For this reason, Shared functions (static in the C# language) have a tiny performance advantage.

Also: In many implementations, instance functions are passed a reference to the instance as the first argument.

Summary. We saw an example of a Shared function and a regular function. Shared members, often called static members, are part of the type, not part of the type's instances. They have advantages and also disadvantages.

But: You can determine whether a function should be shared based on whether it acts upon specific instances or not.