Const. A Const variable cannot be changed. It is immutable. In the VB.NET language, Strings (and other types) can be decorated with the Const keyword.
Const types. Value types such as Integer may also be made constant. This influences performance. Const values resolve faster than regular variables. They should be used when possible.
This program uses a Const at the level of the Module: the syntax here is similar to a field. It also uses a Const at the level of the method: the syntax resembles a local variable Dim.
And The const identifiers "_x" and "name" can be referenced in the same way as variable identifiers.
But You cannot reassign a const. This provokes a compile-time error—the program will not compile.
Module Module1
''' <summary>
''' Const can be Module or Class level.
''' </summary>
Const _x As Integer = 1000
Sub Main()
' Const can be Function or Sub level.
Const name As String = "Sam"' Used as an argument.
Console.WriteLine(name)
Console.WriteLine(_x)
' Constant cannot be the target of an assignment.'_x = 2000
End Sub
End ModuleSam
1000
Performance. Fields and variables—declared with Dim—designate memory locations. When a Dim variable is evaluated, the execution engine reads from that memory location.
But With Const, the compiler inserts the value directly into the intermediate language representation.
So This means that when the method is executed, the value does not require a separate memory access. This slightly improves performance.
Summary. Const values help clear up confusing code. With Const we construct self-documenting code. A Const with the identifier "name" is known to be a name by any programmer reading the code.
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This page was last updated on Sep 24, 2022 (rewrite).