It's not bad. An extension method is a nice choice here. There's no state and you're extending a class that you don't own/can't directly modify. Good design decision. I also like that you're using the Try...Catch paradigm. A common mistake for VB6 devs moving to .Net is carrying over the VB6 error handling pattern.
One thing I don't like about what you've done is this.
Catch ex As Exception
This catches every possible exception in the world, including potentially fatal memory errors. Be as specific as possible when catching exceptions. What specific exception would you expect to happen? Catch that instead, or none at all.
The only other thing I want to mention is that FlagEx is a poor name and the variable itself is kind of useless. Take advantage of the Return statement.
Try
If inArray Is Nothing Then
Return False
ElseIf inArray.Length <= 0 Then
Return False
ElseIf inArray(0) Is Nothing Then
Return False
End If
Catch ex As Exception
FlagEx = False
End Try
Return True
Of course, you could take this a step further by doing away with the Elifs.
Try
If inArray Is Nothing Then Return False
If inArray.Length <= 0 Then Return False
If inArray(0) Is Nothing Then Return False
Catch ex As Exception
FlagEx = False
End Try
Return True
Which leads us to using some short circuiting.
Try
If inArray Is Nothing
OrElse inArray.Length <= 0
OrElse inArray(0) Is Nothing Then
Return False
End If
Catch ex As Exception
FlagEx = False
End Try
Return True
Then flip the condition so we can directly return.
Try
Return (inArray Is Not Nothing
AndAlso inArray.Length > 0
AndAlso inArray(0) Is Not Nothing)
Catch ex As Exception
FlagEx = False
End Try
