Hello
I'm trying to convert the following VB6 code to VB.NET, but can't seem
to find the right API declaration. Note that the Buffer is an output
field which the API call will fill a value in.

VB6 Code:

[VB6]

Type JAG_STRING_40
     Data As String * 40
End Type
Public Declare Function JagRead Lib "jagxapi.dll" (ByVal DataPath As
String, ByVal BufferLen As Integer, Buffer As Any, ReturnLen As Integer)
As Integer

Private Function ReadVariable() as String
    Dim Lit01Val As JAG_STRING_40
    JagRead("/j1/var01", 40, Lit01Val, jagReturnLength)
    ReadVariable = RTrim$(Lit01Val.Data)
end Sub

I tried this declaration, but the returned buffer always seems to be empty:

[VB.NET]

     Private Const BUFFER_LEN As Integer = 40

     <StructLayout(LayoutKind.Sequential)> Private Structure FixLenBuffer
         <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=BUFFER_LEN)>
Public Data As String

         Public Sub New(ByVal vData As String)
             Me.Data = LSet(vData, BUFFER_LEN)
         End Sub

     End Structure

     Private Shared mBuffer As FixLenBuffer

     Private Declare Ansi Function JagReadApi Lib "jagxapi.dll" Alias
"JagRead" (ByVal DataPath As String, ByVal BufferLen As Short, ByRef
Buffer As FixLenBuffer, ByRef ReturnLen As Short) As Short

     Friend Shared Function JagRead(ByVal vVarName As String) As String

         Dim retLen As Short
         mBuffer = New FixLenBuffer("")
         Dim ret As Short = JagReadApi("/j1/" + vVarName, BUFFER_LEN,
mBuffer, retLen)
         Return Trim(Left(mBuffer.Data, retLen))

     End Function



Any help would be greatly appreciated!

Urs

Show quote Hide quote Take a look at the 'VBFixedString' attribute.

Are you looking for someone to totally re-write your finction/API
declaration? If so, attach the 'jagxapi.dll' please

I would also use StringBuilder (Imports System.Text) Class

Declare sb As New System.Text.StringBuilder...

Thanks. It worked well with a Stringbuilder.

Urs

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