Visual Basic® .NET Unleashed

Shadow Variables

Variables can exist in several places and in broader or narrower scopes. Sometimes this causes problems because it may be unclear to the compiler what the code means. For example, when a variable is defined at the procedure level and a variable with the same name exists in a block within the procedure, the variable in the block hides the variable with the same name in the outer scope. In Visual Basic .NET, this is referred to as shadowing. That is, the narrow scope variable shadows the outer scope variable.

At the block level, the compiler will report an error: “Block-level variable hides a variable in an enclosing block.” An example of causation follows:

 Sub Main() Dim V As Object If True Then Dim V As Object V = Nothing End ...