Question

I am reviewing an application and I am wondering which one is more error-prone?

    Public Function ToBool(ByVal vsValue As String) As Boolean

        If IsNothing(vsValue) OrElse vsValue = "" Then
            Return False
        End If
        If UCase(vsValue) = "TRUE" Or vsValue = "1" Or UCase(vsValue) = "Y" Or UCase(vsValue) = "YES" Or UCase(vsValue) = "T" Then
            Return True
        Else
            Return False
        End If
    End Function

or

Public Function ToBool(ByVal vsValue As String) As Boolean

            If IsNothing(vsValue) OrElse vsValue = "" Then
                Return False

            ElseIf UCase(vsValue) = "TRUE" Or vsValue = "1" Or UCase(vsValue) = "Y" Or UCase(vsValue) = "YES" Or UCase(vsValue) = "T" Then
                Return True
            Else
                Return False
            End If
        End Function

Answer 1

There is no difference as to which one is more error prone, as the two code examples are semantically identical. If the code enters the body of the first If block, then in both cases it will exit the function. The code that executes if it does not enter the body of the first If block is also identical.