If merging is VB Migration Partner's ability to merge two or more nested If...End If blocks using the AndAlso operator. This feature is enabled by means of the MergeIfs pragma. To see how this feature works, consider the following VB6 code:
'## MergeIfs True
Sub Test(ByVal x As Integer, y As Integer, z As Integer)
If x > 0 Then
If y = 0 Then
' do something here
' …
If z <> 0 Then
If x < 100 Then
' do something here
' …
End If
End If
End If
If z = 0 Then If x = 10 Then Beep
End If
End Sub
This is the VB.NET code that VB Migration Partner produces:
Public Sub TestX(ByVal x As Short, ByRef y As Short, ByRef z As Short)
' UPGRADE_INFO (#0581): Two nested If...End If blocks have been merged.
If (x > 0) AndAlso (y = 0) Then
' do something here
' ...
' UPGRADE_INFO (#0581): Two nested If...End If blocks have been
' merged.
If (z <> 0) AndAlso (x < 100) Then
' do something here
' ...
End If
' UPGRADE_INFO (#0581): Two nested If...End If blocks have been
' merged.
If (z = 0) AndAlso (x = 10) Then Beep()
End If
End Sub
The effect of this pragma is to simplify the structure of the code, reduce nesting level, and indirectly make it more readable. As you see, the MergeIfs pragma also affects nested single-line Ifs. A warning is automatically added, so that you can quickly revise all points where this optimization was applied.
By default, test expressions are enclosed between parenthesis, so that you easily see how each If statement contributed to the compound expression. If you don’t like these extra parenthesis, just specify False as the pragmas’s second argument:
'## MergeIfs True, False
The MergeIfs pragma can have project-, file-, and method-level scope, therefore you can precisely define where this optimization should be applied. In most cases you can safely specify project-level If merging by including the following line in the VBMigrationPartner.pragmas file:
'## project:MergeIfs True