Recently we added some support for migrating the IsMissing function to VB.NEt or C#
The thing is. In VB6 the IsMissing Function is TRUE only if you have something like:
Public Sub Foo(Optional str)
Where you dont specify the variable type, or if you have
Public Sub Foo(Optional str as Variant)
And is IsMissing is FALSE for any other case. Including Optional variables whose definition type is not Variant.
So let's see some examples to illustrate the idea:
Example 1:
Public Sub Foo(str, a As Integer, b As Integer, Optional c As Integer)
MsgBox (str & "Foo Is missing a " & IsMissing(a))
MsgBox (str & "Foo Is missing b " & IsMissing(b))
MsgBox (str & "Foo Is missing c " & IsMissing(c))
End Sub
It occurs that IsMissing is really FALSE in all cases. So it is equivalent to:
Public Sub Foo(str, a As Integer, b As Integer, Optional c As Integer)
MsgBox (str & "Foo Is missing a " & false)
MsgBox (str & "Foo Is missing b " & false)
MsgBox (str & "Foo Is missing c " & false)
End Sub
Example 2:
Public Sub Goo(str, a As Integer, b As Integer, Optional c As Object, Optional d As Byte, Optional e)
MsgBox (str & "Goo Is missing a" & IsMissing(a))
MsgBox (str & "Goo Is missing b" & IsMissing(b))
MsgBox (str & "Goo Is missing c" & IsMissing(c))
MsgBox (str & "Goo Is missing d" & IsMissing(d))
MsgBox (str & "Goo Is missing e" & IsMissing(e))
End Sub
All cases EXCEPT "e" are equivalent to FALSE
Public Sub Goo(str, a As Integer, b As Integer, Optional c As Object, Optional d As Byte, Optional e)
MsgBox (str & "Goo Is missing a" & false)
MsgBox (str & "Goo Is missing b" & false)
MsgBox (str & "Goo Is missing c" & false)
MsgBox (str & "Goo Is missing d" & false)
MsgBox (str & "Goo Is missing e" & IsMissing(e))
End Sub
So if you are migrating your VB6 Code to C# put attention to these little details it can save you a lot of time.And remember that this is just one feature of VBCompanion tool ;)