[RESOLVED] VB.Net 2005 and Fixed Length Variables???

[blakemckenna]

Can VB.Net 2005 assign fixed lengths to string variables?

Ex:

Dim strVar as string * 25

I know in VB6 you can do this. If this can't be done....what is the best way to create a text file with fixed length fields?

Thanks,

[jmcilhinney]

No it can't. You can apply the VBFixedString attribute to a String field, but that does not make the managed string a fixed length. That makes it appear as though it is a fixed length when passed to unmanaged code, so it is only used in instances where an API function requires a structure with fixed length fields.

If you want to create fixed-width column sin a text file then you should use the String.PadRight method. For instance, if you want a column of data in a text file that is 20 characters wide then do this:

myStreamWriter.Write(myString.PadRight(20))

That will return a string that is 20 characters wide and write it to the stream. If your original string is less than 20 characters long it will be padded with enough spaces to make it 20 characters wide.

[blakemckenna]

Thanks JMC....I'll give that a try and see if it produces what I need!

[blakemckenna]

JMC,

I try this and I get an error. The way I'm doing it isn't exactly as you have it. Here is my code:

    Private Sub WriteOutputFile(ByVal recType As String)
        Try
            Dim strDetailLine As String = ""

            Select Case recType
                Case "POSBH"
                    strDetailLine = stcBatchHdr.recType.PadRight(5) & _
                                    stcBatchHdr.merchBatchLvlDiscData.PadRight(25) & _
                                    stcBatchHdr.locationCD.PadRight(14) & _
                                    stcBatchHdr.merchBatchID.PadRight(10) & _
                                    stcBatchHdr.submissionDate.PadRight(6) & _
                                    stcBatchHdr.submissionTime.PadRight(6) & _
                                    stcBatchHdr.creationDate.PadRight(6) & _
                                    stcBatchHdr.filler.PadRight(628)
                    W1.WriteLine(strDetailLine)
                Case "POSTH"
                    W1.WriteLine(stcTransHdr)
                Case "MOFUL"
                    W1.WriteLine(stcMobile)
                Case "POSTD"
                    W1.WriteLine(stcProduct)
                Case "POSTT"
                    W1.WriteLine(stcTransTrailer)
                Case "POSBT"
                    W1.WriteLine(stcBatchTrailer)
            End Select

        Catch ex As Exception
            strProcedure = "WriteOutputFile()"
            Msg = ex.Message
            ErrorHandler(strModule, strProcedure, Msg)
        End Try
    End Sub

When I run this, I get the error:

"Ojbect reference not set to an instance of an object"

on the highlighted code!

[jmcilhinney]

And what reference is Nothing? Use the debugger. That issue is nothing to do with PadRight specifically. It means that you're trying to call a method on a member that is returning Nothing. It's up to you to make sure that your references are not Nothing before attempting to use them.

[blakemckenna]

If I leave the statement just as it is except remove the PadRight parameters...it works fine!

    Private Sub WriteOutputFile(ByVal recType As String)
        Try
            Dim strDetailLine As String = ""

            Select Case recType
                Case "POSBH"
                    strDetailLine = stcBatchHdr.recType & _
                                    stcBatchHdr.merchBatchLvlDiscData & _
                                    stcBatchHdr.locationCD & _
                                    stcBatchHdr.merchBatchID & _
                                    stcBatchHdr.submissionDate & _
                                    stcBatchHdr.submissionTime & _
                                    stcBatchHdr.creationDate & _
                                    stcBatchHdr.filler                    
                    W1.WriteLine(strDetailLine)
                Case "POSTH"
                    W1.WriteLine(stcTransHdr)
                Case "MOFUL"
                    W1.WriteLine(stcMobile)
                Case "POSTD"
                    W1.WriteLine(stcProduct)
                Case "POSTT"
                    W1.WriteLine(stcTransTrailer)
                Case "POSBT"
                    W1.WriteLine(stcBatchTrailer)
            End Select

        Catch ex As Exception
            strProcedure = "WriteOutputFile()"
            Msg = ex.Message
            ErrorHandler(strModule, strProcedure, Msg)
        End Try
    End Sub

[stanav]

What are the types of these?

stcBatchHdr.recType
stcBatchHdr.merchBatchLvlDiscData
stcBatchHdr.locationCD
stcBatchHdr.merchBatchID
stcBatchHdr.submissionDate
stcBatchHdr.submissionTime
stcBatchHdr.creationDate                                    
stcBatchHdr.filler

If they are string then you should initialize them propriately when declared such as in this example

'Declare a string without initialize it will throw null exception
Dim s As String
MsgBox(s.PadRight(10))  's is Nothing, thus when you try to do PadRight it'll throw a null exception on this line

'The code above can be fixed by properly initialize the variable
Dim s As String = String.Empty 
MsgBox(s.PadRight(10))

[blakemckenna]

Stanav,

I like to use Structures. Here is the definition!

    Public Structure BatchHeader
        Dim recType As String
        Dim merchBatchLvlDiscData As String
        Dim locationCD As String
        Dim merchBatchID As String
        Dim submissionDate As String
        Dim submissionTime As String
        Dim creationDate As String
        Dim filler As String
    End Structure
    Public stcBatchHdr As BatchHeader

Is there anyway of writing a Function where I can pass the field/variable, it's desired length, and return a value with the appropriate width?

Thanks,

[stanav]

Stanav,

I like to use Structures. Here is the definition!

    Public Structure BatchHeader
        Dim recType As String
        Dim merchBatchLvlDiscData As String
        Dim locationCD As String
        Dim merchBatchID As String
        Dim submissionDate As String
        Dim submissionTime As String
        Dim creationDate As String
        Dim filler As String
    End Structure
    Public stcBatchHdr As BatchHeader

Is there anyway of writing a Function where I can pass the field/variable, it's desired length, and return a value with the appropriate width?

Thanks,

Using a structure is OK, you just have to properly initialize it.
Since you've declared a variable type BatchHeader, just make sure to initialize it before using. .. So somewhere in the code, you just do this then it should work.

stcBatchHdr.recType = String.Empty
stcBatchHdr.merchBatchLvlDiscData = String.Empty
stcBatchHdr.locationCD = String.Empty
stcBatchHdr.merchBatchID = String.Empty
stcBatchHdr.submissionDate = String.Empty
stcBatchHdr.submissionTime = String.Empty
stcBatchHdr.creationDate = String.Empty                                    
stcBatchHdr.filler = String.Empty

Alternatively, you can make BatchHeader a class instead of structure and initialize all variables in the Sub New of the class.

[jmcilhinney]

If you were to use properties instead of fields then this would all be easy. That's what properties are for. E.g.

Public Structure BatchHeader
 
    Private _recType As String
    Private _recTypeWidth As UShort
 
    Public Property RecType As String
        Get
            If Me._recType Is Nothing
                Me._recType = String.Empty
            End If
 
            Return Me._recType.PadRight(CInt(Me._recTypeWidth))
        End Get
        Set(ByVal value As String)
            Me._rectType = value
        End Set
    End Property
 
    Public Property RecTypeWidth As UShort
        Get
            Return Me._recTypeWidth
        End Get
        Set(ByVal value As UShort)
            Me._rectTypeWidth = value
        End Set
    End Property
 
    '....
 
End Structure

[blakemckenna]

To initialize, how about just

stcBatchHdr = Nothing

[jmcilhinney]

That doesn't help because the problem is that your String fields ARE Nothing by default. Unless you initialise them with a String object then those fields refer to no object and you cannot call the PadRight method of an object that doesn't exist. If your type was a class instead of a structure then you could initialise the String fields to an empty string on the line that declares them. That's not possible with a structure.