VB.NETの条件判断構文（If）の使い方いろいろ

If boolean-expression  Then

End If

If Not boolean-expression  Then

End If

If varname Is Nothing Then      ' Not  varname Is Nothing

End If

If varname Is String.Empty Then      ' Dim varname As String

End If

If varname.Equals(String.Empty) Then

End If

If varname = String.Empty Then

End If

If varname = "" Then      ' Dim varname As String

End If

If varname.Equals("") Then

End If

If varname Is Nothing OrElse varname.Length = 0 Then

End If

If boolean-expression  Then

ElseIf boolean-expression Then

Else

End If

If boolean-expression1 AndAlso boolean-expression2 Then

End If

If boolean-expression1 And boolean-expression2 Then

End If

If boolean-expression1 OrElse boolean-expression2 Then

End If

If boolean-expression1 Or boolean-expression2 Then

End If