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Showing SKILL.md
| name | vb6-legacy |
| description | Classic VB6 patterns, COM interop, migration strategies |
| user-invocable | false |
| disable-model-invocation | true |
| version | 1.0.0 |
| category | toolchain |
| author | Claude MPM Team |
| license | MIT |
| tags | ["visualbasic","vb6","legacy","com","interop","migration"] |
Patterns for maintaining VB6 code and strategies for migrating to VB.NET with COM interop.
' VB6 - Variant types
Dim data As Variant
data = 123
data = "Hello"
' VB.NET - Strong typing with Option Strict On
Option Strict On
Dim data As Object ' Still avoid when possible
Dim number As Integer = 123
Dim text As String = "Hello"
' VB6 - Default properties
Text1.Text = "Hello"
Text1 = "Hello" ' Uses default Text property
' VB.NET - Explicit properties required
TextBox1.Text = "Hello" ' Must be explicit
' VB6 - ByRef default
Sub ProcessData(data As String) ' ByRef by default
' VB.NET - ByVal default
Sub ProcessData(data As String) ' ByVal by default
Sub ProcessData(ByRef data As String) ' Explicit ByRef
' VB6 - On Error
On
ErrorHandler
ex Exception
' VB6 - Fixed-length strings
Dim name As String * 50
' VB.NET - Use regular string and PadRight
Dim name As String = "John".PadRight(50)
' VB6 - Currency type
Dim amount As Currency
' VB.NET - Use Decimal
Dim amount As Decimal
' VB6 - Control arrays
Dim TextBox(5) As TextBox
' VB.NET - Use collection
Dim textBoxes As New List(Of TextBox)()
' VB6 - Let/Set keywords
Let x = 5
Set obj = New MyClass
' VB.NET - Assignment without keywords
Dim x As Integer = 5
Dim obj As New MyClass()
' Add COM reference in project
' Tools -> Add Reference -> COM -> Excel Object Library
Imports Excel = Microsoft.Office.Interop.Excel
Public Sub ExportToExcel(data As DataTable)
Dim excelApp As Excel.Application = Nothing
Dim workbook As Excel.Workbook = Nothing
Dim worksheet As Excel.Worksheet = Nothing
Try
excelApp = New Excel.Application()
workbook = excelApp.Workbooks.Add()
worksheet = CType(workbook.Worksheets(1), Excel.Worksheet)
' Write headers
For col = 0 To data.Columns.Count - 1
worksheet.Cells(1, col + 1) = data.Columns(col).ColumnName
Next
' Write data
For row = 0 To data.Rows.Count - 1
For col = 0 To data.Columns.Count - 1
worksheet.Cells(row + 2, col + 1) = data.Rows(row)(col)
Next
Next
excelApp.Visible = True
Catch ex As Exception
MessageBox.Show($"Excel export failed: {ex.Message}")
Finally
' Release COM objects
If worksheet IsNot Nothing Then
System.Runtime.InteropServices.Marshal.ReleaseComObject(worksheet)
End If
If workbook IsNot Nothing Then
System.Runtime.InteropServices.Marshal.ReleaseComObject(workbook)
End If
If excelApp IsNot Nothing Then
System.Runtime.InteropServices.Marshal.ReleaseComObject(excelApp)
End If
End Try
End Sub
Imports System.Reflection
Public Sub CreateExcelLateBound()
Dim excelType As Type = Type.GetTypeFromProgID("Excel.Application")
If excelType Is Nothing Then
MessageBox.Show("Excel not installed")
Return
End If
Dim excelApp As Object = Nothing
Try
' Create COM object
excelApp = Activator.CreateInstance(excelType)
' Call methods via reflection
excelType.InvokeMember("Visible",
BindingFlags.SetProperty,
Nothing,
excelApp,
New Object() {True})
Dim workbooks As Object = excelType.InvokeMember("Workbooks",
BindingFlags.GetProperty,
Nothing,
excelApp,
Nothing)
' Add workbook
workbooks.GetType().InvokeMember("Add",
BindingFlags.InvokeMethod,
Nothing,
workbooks,
Nothing)
Finally
If excelApp IsNot Nothing Then
System.Runtime.InteropServices.Marshal.ReleaseComObject(excelApp)
End If
End Try
End Sub
' ✅ Good: Proper COM object cleanup
Public Sub UseComObject()
Dim excelApp As Excel.Application = Nothing
Dim workbook As Excel.Workbook = Nothing
Try
excelApp = New Excel.Application()
workbook = excelApp.Workbooks.Add()
' Use objects
Finally
' Release in reverse order of creation
If workbook IsNot Nothing Then
workbook.Close(False)
Marshal.ReleaseComObject(workbook)
workbook = Nothing
End If
If excelApp IsNot Nothing Then
excelApp.Quit()
Marshal.ReleaseComObject(excelApp)
excelApp = Nothing
End If
GC.Collect()
GC.WaitForPendingFinalizers()
End Try
End Sub
' ❌ Bad: Not releasing COM objects (memory leak)
Dim excelApp = New Excel.Application()
excelApp.Workbooks.Add()
' No cleanup - Excel process remains in memory!
Imports System.Runtime.InteropServices
<ComVisible(True)>
<Guid("12345678-1234-1234-1234-123456789012")>
<ClassInterface(ClassInterfaceType.None)>
<ProgId("MyCompany.Calculator")>
Public Class Calculator
Implements ICalculator
Public Function Add(a As Integer, b As Integer) As Integer Implements ICalculator.Add
Return a + b
End Function
Public Function Subtract(a As Integer, b As Integer) As Integer Implements ICalculator.Subtract
Return a - b
End Function
End Class
' Interface for COM
<ComVisible(True)>
<Guid("87654321-4321-4321-4321-210987654321")>
<InterfaceType(ComInterfaceType.InterfaceIsDual)>
Public Interface ICalculator
Function Add(a As Integer, b As Integer) As Integer
Function Subtract(a As Integer, b As Integer) As Integer
End Interface
# Register assembly for COM
regasm MyAssembly.dll /tlb /codebase
# Unregister
regasm MyAssembly.dll /u
# Generate type library
tlbexp MyAssembly.dll
' VB6 style (avoid in new code)
Public Function GetCustomer(id As Integer) As Customer
On Error GoTo ErrorHandler
' Code here
Exit Function
ErrorHandler:
MsgBox "Error: " & Err.Description
Resume Next
End Function
' VB.NET modern style
Public Function GetCustomer(id As Integer) As Customer
Try
' Code here
Catch ex As ArgumentException
MessageBox.Show($"Invalid argument: {ex.Message}")
Return Nothing
Catch ex As Exception
MessageBox.Show($"Error: {ex.Message}")
Throw
End Try
End Function
' VB6 style (avoid)
Dim fileNum As Integer = FreeFile()
FileOpen(fileNum, "data.txt", OpenMode.Output)
PrintLine(fileNum, "Hello World")
FileClose(fileNum)
' VB.NET modern style
Using writer = New StreamWriter("data.txt")
writer.WriteLine("Hello World")
End Using
' Or async
Await File.WriteAllTextAsync("data.txt", "Hello World")
' VB6 Collection (avoid in new code)
Dim customers As New Collection()
customers.Add(customer, "key1")
Dim item = customers("key1")
' VB.NET generic collections
Dim customers = New Dictionary(Of String, Customer)()
customers.Add("key1", customer)
Dim item = customers("key1")
' Or List(Of T)
Dim customerList = New List(Of Customer)()
customerList.Add(customer)
' 1. Start with COM interop wrapper
' Wrap VB6 COM component in VB.NET
Public Class VB6Wrapper
Private vb6Component As Object
Public Sub New()
vb6Component = CreateObject("VB6Project.Component")
End Sub
Public Function ProcessData(data As String) As String
Return vb6Component.ProcessData(data).ToString()
End Function
End Class
' 2. Gradually replace with native VB.NET
Public Class ModernComponent
Public Function ProcessData(data As String) As String
' New VB.NET implementation
Return data.ToUpper()
End Function
End Class
' Use modern VB.NET features in new code
Option Strict On
Option Explicit On
' Release COM objects explicitly
Marshal.ReleaseComObject(comObject)
GC.Collect()
' Use Try-Catch instead of On Error
Try
' Code
Catch ex As Exception
' Handle
End Try
' Use generics instead of Collections
Dim items = New List(Of Customer)()
' Use async for I/O
Await File.WriteAllTextAsync("file.txt", content)
' Don't use VB6 compatibility module
Imports Microsoft.VisualBasic.Compatibility.VB6 ' Legacy only!
' Don't use Option Strict Off
Option Strict Off ' Avoid!
' Don't use On Error in new code
On Error Resume Next ' VB6 style
' Don't forget to release COM objects
Dim excelApp = New Excel.Application()
' ... (no cleanup - memory leak!)
' Don't use late binding when early binding available
Dim obj = CreateObject("Excel.Application") ' Use typed reference instead