Visual Basic 2012 Programmer's Reference

RELAXED DELEGATES

If you assign a variable to the value in a variable of a different type, Visual Basic automatically converts the value into the correct type under some circumstances. If you set a Single variable equal to an Integer variable, Visual Basic automatically converts the Integer into a Single.

If Option Strict is off, you can also do the reverse: If you assign an Integer variable equal to a Single variable, Visual Basic converts the Single into an Integer (if it can).

In a similar manner, relaxed delegates let Visual Basic convert method parameters from one data type to another under certain circumstances. If the code invokes a subroutine by using a delegate, Visual Basic tries to convert parameters when it can. Probably the easiest way to understand how this works is to consider an example.

The following code declares a delegate type named TestDelegate. Methods that match this delegate should be subroutines that take a Control as a parameter.

' Declare the delegate type.
Private Delegate Sub TestDelegate(ctl As Control)

The following code defines three subroutines that take parameters of different types. The first takes an Object as a parameter, the second takes a TextBox, and the third takes no parameters. Note that the first subroutine cannot work if Option Strict is on. Option Strict disallows late binding, so the code cannot use a Text property provided by a generic Object.

' A more general parameter type. Private Sub Test1(obj As Object) obj.Text = "Test1" ' Needs ...