VB6 C# VB Code Converter

Editorial Note

This article appears in the Third Party Products and Tools section. Articles in this section are for the members only and must not be used to promote or advertise products in any way, shape or form. Please report any spam or advertising.

Downloads
Background
Before Conversion
SharpDevelop
VB6 Upgrade Companion
Other Converters

Downloads

Background

This article is about converting code to VB.Net.
It will discus SharpDevelop IDE and VB6 Upgrade Companion.

SharpDevelop IDE and NRefactory cover many conversion between deferent languages (C#, VB.Net, boo, Python, Ruby) and most other C# VB converter use the library NRefactory.

VB6 Upgrade Companion witch will convert VB6 codes to C# or VB.Net. This software is selected because it is the only Microsoft partner to upgrade VB6

Before Conversion

Make sure your code can be recompiled and run well before start converting.
For C# and VB.Net 100% code conversion maybe get in many causes but not always. In many cases many post conversion fixing is required.
No convertors can grantee the 100% conversion.
For other language pairs: Make sure the the target language support your project type.
Please note the VB6 converting is a hard work because of the programing language philosophy is defer. please see VB6 section later is this article

SharpDevelop

Lots of C# <> VB code converter are available all most all of them are using Refactory library form SharpDevelop IDE to make the conversion and them make some useful post conversion fixing.

The power of NRefactory is parsing the code before the conversion; even if a keyword could take more than one meaning it could be converted correctly because of understanding the code line before the conversion. an other thing will make the converting is possible in most cases.

About SharpDevelop

It's an freeware Open Source Development Environment for .NET.
It could be used to make many useful code conversion.
SharpDevelop IDE is the mother of NRefactory library which is the most uses converting library
The conversion that done using SharpDevelop IDE is much beater.
It provide a wide range of code conversion C#, VB.NET, Boo, Python, Ruby

About NRefactory:

ICSharpCode.NRefactory is freely available as a part of SharpDevelop IDE.
It is parser library for C# and VB.
It consists of a single Abstract Syntax Tree (AST) that can represent all constructs that are available in C# or VB (unlike System.CodeDom, which only represents constructs common to C# and VB).
By using the C# parser and a VB output visitor (or vice versa), you can do a code converter.
After parsing to AST, you can analyze and/or transform the AST and re-create source code from the (modified) AST, then re-insert the comments we saved from the parser into the output
For more info about NRefactory please see: sharpdevelop.net and NRefactory wiki.
You may try samples\NRefactoryDemo in the SharpDevelop source code to take a look how the AST parse source code.

About AST and Parsing:

The following example show a simple parsing proses.

SharpDevelop IDE and C# VB converters:

Application	Conversion Technique	What to convert	Conversion	Notes
SharpDevelop IDE	Developer IDE freeware	Code & file	C#, VB.Net, boo, Python, Ruby	Best Free converter
Econ NetVert	Use NRefactory	Code & file	C# <> VB.Net
On Line Converter	Web page Online service	CCode only	C# <> VB.Net
Instant VB	Share ware Internal Converter	Code, file & folder	Special version for each conversion convert between: C#, VB.Net, C++, Java	Very Flexible
VB.Net to C# Converter	Use NRefactory	Code & file	VB.Net > C#
Convert .NET	Use NRefactory	Code only	C# <> VB.Net
C# to VB.NET Project Converter	Use NRefactory	Projects	C# > VB.Net

What in C# that has no equivalent is VB:

C# Fixed-size buffers and fixed statement has no equivalent in VB:
```
private fixed char name[30]
```
C# fixed block has no equivalent in VB:
Enter the fixed keyword. When used for a block of statements, it tells the CLR that the object in question cannot be relocated, and thus, it ends up pinning the object. Thus, when pointers are used in C#, the fixed keyword is used pretty often to prevent invalid pointers at runtime. Lets have a look at how it works:

C# Generic indexers and properties has no equivalent in VB:

public T this[string key] 
{ 
	get { /* Return generic type T. */ } 
}
public T GetItem<T>(string key) 
{ 
	/* Return generic type T. */ 
}

C# Generic operators has no equivalent in VB:

public static T operator +<T>(T a, T b)	
{
// Do something with a and b that makes sense for operator + here
}

C# #undef has no equivalent in VB.
C# volatile/checked/unchecked/stackalloc has no equivalent in VB:
Using the unchecked statement with constant expressions Overflow is unchecked at compile time or run time and the return value be deffer

C# unsafe block has no equivalent in VB:

unsafe static void FastCopy ( byte[] src, byte[] dst, int count )
{
// unsafe context: can use pointers here
}

C# extern alias has no equivalent in VB:
It can sometimes be necessary to reference two versions of assemblies that have the same fully-qualified type names, for example when you need to use two or more versions of an assembly in the same application. By using an external assembly alias, the namespaces from each assembly can be wrapped inside root-level namespaces named by the alias, allowing them to be used in the same file
To reference two assemblies with the same fully-qualified type names, an alias must be specified on the command line, as follows:
```
/r:GridV1=grid.dll
/r:GridV2=grid20.dll 
```
This creates the external aliases GridV1 and GridV2. To use these aliases from within a program, reference them using the extern keyword. For example:
```
extern alias GridV1; 
extern alias GridV2;
```
C# overloading ++ or -- operator in has no equivalent in VB: ++ & -- can converted easily but overloading is not.
C# ?? operator has no equivalent in VB:
C# yield keyword has no equivalent in VB:
If return value is IEnumerable then multi return statement is allowed by using yield return

What in VB that has no equivalent is C#:

VB parameterized properties has no equivalent in C#

Public Property MyProperty(ByVal A As String) As String
    Get
        Return 2 * A
    End Get
    Set(ByVal value As String)
        A = value / 2
    End Set
End Property

VB Numeric labels, On Error, Resume Next, Continue and Err object has no equivalent in C#

Sub Test()
    On Error Resume Next
    Err.Raise(1000)
    On Error GoTo 0
    Err.Raise(1001)
    On Error GoTo -1
    Err.Raise(1002)
    On Error GoTo EH
    Err.Raise(1003)
    Exit Sub
EH:
    MsgBox(Err.Description)
    Resume Next
End Sub

VB IIf is some who defer than if in C#.
```
A = IIf(E, B, A)
```
VB ReDim Preserve has no built-in equivalent in C#
```
ReDim Preserve A(9)
```

VB Select Case: switch is not as flexible as Select Case and many VB Select Case blocks cannot be converted to switch

Select Case A
    Case 1 To 10
        '
    Case Is < 2 * A
        '
    Case Is > 30
        '
End Select

VB Procedures local static variables has no built-in equivalent in C# but class-level private variable may used.

Sub Test()
    Static InUse As Boolean = False
    If InUse Then Exit Sub
    'Run Once code
    InUse = True
    '
End Sub

VB With has no equivalent in C#.

With Me
    .Width = 10
    .Top = 0
End With

VB Import Shared Class member is not supported in C#
```
Imports WindowsApplication1.Form1
```
VB Exit try
VB Exit statements that not matching the immediately enclosing block.
VB Member names can be the same as their enclosing type but in C# can't.
VB #Const can be set to any value but in C# accept constants only
```
#Const C = 2 * A
```
VB MyClass has no equivalent in C# (some time using this is OK)
In C#, an object cannot reference itself in its class-level declarations: You cannot use this in class-level declarations in C#.
In C#, an object cannot reference its base class in its class-level declarations: You cannot use base in class-level declarations in C#.
Numeric labels are not allowed in C#: You must change the label to be a standard C# identifier.
VB &O has no equivalent in C#
VB When has no equivalent in C#
VB has some operator that are not present in C# and can't be overloaded in C# in any way such as(integer division (VB \), Like, exponentiation (VB ^))
VB Method with the same name as the Class name is used for constructor in C# and can't use for any other in C#.
VB integer casts convert 'True' to -1, but System.Convert methods convert 'True' to 1.

C# and VB Language Equivalents and Comparison:

Using SharpDevelop as a code converter:

Run SharpDevelop IDE
From file menu select open - project/solution and open the project to be converted
From View menu select projects
In the project window select the project to be converted
from project menu choose convert and then choose the target language
This will convert the whole project
The conversion could be done by right clicking the project icon in the project window then choose convert

SharpDevelop Points of Interest

How to covert C# code:

The code is converted using ICSharpCode.NRefactory.ParserFactory class:

Converter code in VB:

Imports ICSharpCode.NRefactory
Imports ICSharpCode.NRefactory.PrettyPrinter
Imports System.IO

Public Class CS2VB

    Public Overrides Function ConvertCode(ByVal sourceCode As String) As String        
            
            Dim specials As IList(Of ISpecial)
            Dim result As Ast.CompilationUnit
            Dim Parse_errors = ""
            Using parser As IParser = ParserFactory.CreateParser( _
                 SupportedLanguage.CSharp, New StringReader(sourceCode))
                parser.Parse()
                'this allows retrieving comments, preprocessor directives, etc. 
                '(stuff that isn't part of the syntax)
                specials = parser.Lexer.SpecialTracker.RetrieveSpecials()
                'this retrieves the root node of the result AS
                result = parser.CompilationUnit
                If parser.Errors.Count > 0 Then
                    Parse_errors = parser.Errors.ErrorOutput
                End If
            End Using

            'Now you can analyze and/or transform the AST.
            'Should you want to re-create source code from the (modified) AST, 
            'use an output visitor: 
            're-insert the comments we saved from the parser into the output
            
            Dim outputVisitor As New PrettyPrinter.VBNetOutputVisitor
            Dim astViewUnit = result
            Using SpecialNodesInserter.Install(specials, outputVisitor)
                astViewUnit.AcceptVisitor(outputVisitor, Nothing)
            End Using
            Dim outputCode = outputVisitor.Text
            'By using the C# parser and a VB output visitor (or vice versa), 
            'you can build a code converter. Of course, 
            'the real Code Converter in SharpDevelop also transforms the AST to fix cases 
            'where C# and VB semantics differ.

            Return outputCode   

    End Function
End Class/pre>

Converter code in C#:

using ICSharpCode.NRefactory;
using ICSharpCode.NRefactory.PrettyPrinter;
using System.IO;

public class CS2VB
{

    public override string ConvertCode(string sourceCode)
    {
        //var names and format is as in http://wiki.sharpdevelop.net/NRefactory.ashx

        //ICSharpCode.NRefactory is a parser library for C# and VB.
        //It consists of a single Abstract Syntax Tree (AST) 
        //that can represent all constructs that are available in C# or VB 
        //(unlike System.CodeDom, which only represents constructs common to C# 
        //and VB).
        //Please try samples\NRefactoryDemo in the SharpDevelop source code 
        //to take a look at the AST
        //To parse source code, use: 
        IList specials;
        Ast.CompilationUnit result;
        object Parse_errors = "";
        using (IParser parser = ParserFactory.CreateParser(SupportedLanguage.CSharp, new 
                StringReader(sourceCode))) {
            parser.Parse();
            // this allows retrieving comments, preprocessor directives, etc. 
            //(stuff that isn't part of the syntax)
            specials = parser.Lexer.SpecialTracker.RetrieveSpecials();
            // this retrieves the root node of the result AST
            result = parser.CompilationUnit;
            if (parser.Errors.Count > 0) {
                MessageBox.Show(parser.Errors.ErrorOutput, "Parse errors");
            }
        }
        //Now you can analyze and/or transform the AST.
        //Should you want to re-create source code from the (modified) AST, 
        //use an output visitor: 
        //re-insert the comments we saved from the parser into the output
        PrettyPrinter.VBNetOutputVisitor outputVisitor = new 
                PrettyPrinter.VBNetOutputVisitor();
        object astViewUnit = result;
        using (SpecialNodesInserter.Install(specials, outputVisitor)) {
            astViewUnit.AcceptVisitor(outputVisitor, null);
        }
        object outputCode = outputVisitor.Text;
        //By using the C# parser and a VB output visitor (or vice versa), 
        //you can build a code converter. Of course, 
        //the real Code Converter in SharpDevelop also transforms the AST 
        //to fix cases 
        //where C# and VB semantics differ.

        return outputCode;

    }
}

Demo conversion:

Partial code convert is not supported code should be in class and in method.

Demo1:

class Class1{void sub1(){
    //your code start
    int x =0;
    //your code end
}}

The result in VB

Class Class1
    Sub sub1()
        'your code start
        Dim x As Integer = 0
        'your code end
    End Sub
End Class

Demo 2:

namespace WindowsFormsApplication1{
    partial class Form1
    {
        private System.ComponentModel.IContainer components = null;
		private System.Windows.Forms.TextBox textbox1;
        private System.Windows.Forms.TextBox textbox2;

        
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        private void InitializeComponent()
        {
            this.textbox1 = new System.Windows.Forms.TextBox();
            this.textbox2 = new System.Windows.Forms.TextBox();
            this.SuspendLayout();
            // 
            // textbox1
            // 
            this.textbox1.Location = new System.Drawing.Point(30, 30);
            this.textbox1.Name = "TEXTBOX1";
            this.textbox1.Size = new System.Drawing.Size(80, 20);
            this.textbox1.TabIndex = 0;
            // 
            // textbox2
            // 
            this.textbox2.Location = new System.Drawing.Point(30, 60);
            this.textbox2.Name = "textbox";
            this.textbox2.Size = new System.Drawing.Size(80, 20);
            this.textbox2.TabIndex = 1;
            this.textbox2.TextChanged += new System.EventHandler(this.textbox_TextChanged);
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(284, 262);
            this.Controls.Add(this.textbox2);
            this.Controls.Add(this.textbox1);
            this.Name = "Form1";
            this.Text = "Form1";
            this.ResumeLayout(false);
            this.PerformLayout();

        }
        
        public Form1()
        {
            InitializeComponent();
        }

        private void textbox_TextChanged(object sender, EventArgs e)
        {
            string x = "";
            string X = "";
        }
    }
}

The result in VB

Namespace WindowsFormsApplication1
	Partial Class Form1
		Private components As System.ComponentModel.IContainer = Nothing
		Private textbox1 As System.Windows.Forms.TextBox
		Private textbox2 As System.Windows.Forms.TextBox


		Protected Overrides Sub Dispose(disposing As Boolean)
			If disposing AndAlso (components IsNot Nothing) Then
				components.Dispose()
			End If
			MyBase.Dispose(disposing)
		End Sub

		Private Sub InitializeComponent()
			Me.textbox1 = New System.Windows.Forms.TextBox()
			Me.textbox2 = New System.Windows.Forms.TextBox()
			Me.SuspendLayout()
			' 
			' textbox1
			' 
			Me.textbox1.Location = New System.Drawing.Point(30, 30)
			Me.textbox1.Name = "TEXTBOX1"
			Me.textbox1.Size = New System.Drawing.Size(80, 20)
			Me.textbox1.TabIndex = 0
			' 
			' textbox2
			' 
			Me.textbox2.Location = New System.Drawing.Point(30, 60)
			Me.textbox2.Name = "textbox"
			Me.textbox2.Size = New System.Drawing.Size(80, 20)
			Me.textbox2.TabIndex = 1
			AddHandler Me.textbox2.TextChanged, New System.EventHandler(AddressOf Me.textbox_TextChanged)
			' 
			' Form1
			' 
			Me.AutoScaleDimensions = New System.Drawing.SizeF(6F, 13F)
			Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
			Me.ClientSize = New System.Drawing.Size(284, 262)
			Me.Controls.Add(Me.textbox2)
			Me.Controls.Add(Me.textbox1)
			Me.Name = "Form1"
			Me.Text = "Form1"
			Me.ResumeLayout(False)
			Me.PerformLayout()

		End Sub

		Public Sub New()
			InitializeComponent()
		End Sub

		Private Sub textbox_TextChanged(sender As Object, e As EventArgs)
			Dim x__1 As String = ""
			Dim X__2 As String = ""
		End Sub
	End Class
End Namespace

Conversion Cases:

Case sensitive C# to VB:

The converter will automatically rename object if needed.

Event Handler C# to VB:

The event C# handler will be converted as follows:

C#:

this.textbox2.TextChanged += new System.EventHandler(this.textbox_TextChanged);

VB:

AddHandler Me.textbox2.TextChanged, New System.EventHandler(AddressOf Me.textbox_TextChanged)

VB6 Upgrade Companion VBUC:

If you are not familiar with upgrading VB6 then you will not under stand how useful the software. It same too much of the upgrade time also it is in most time required many post conversion works.
It is much better than the old upgrade engine that is included in versions 2003, 2005 and 2008 of VS

VB 6.0 upgrading advantages

Supporting 64 bit
Faster running
More resources
Improve the maintenance of an application
Increase developer productivity

VB 6.0 upgrading disadvantages

Compile on demand will be lost.
The resulting application need dot net farmworker will the original one is not
If your application is a dynamic library; note that pre declared object is not supported in C# or vb.Net.
If your application is ActiveX control or ActiveX Document then there is no acceptable converter for you; manual code rewriting is needed.
The converter we save your time for converting but post conversion work is much needed.

What VBUC can upgrade:

Modules, Classes, Forms & MDIForms
User Controls that used in the same project on in the same group
Resource File

What VBUC can't upgrade:

Property Page
Designer files (*.Dsr)
User Controls that used in web browser or ActiveX container
ActiveX Document

Before Using VBUC:

The VBUC is feather software with many option and we should study before start converting:

It is better to install VB6 but it is not a must
Ensure that your application could be recompiled and run correctly.
Ensure that all your referred library are available and work well in the current operating system.
It is more simple to convert to VB.Net than C#.
For ActiveX choose Com Visible
Form options Use helper classes whenever it available
For making you application more like .net designed use More dot net option
If the above option fail use the More Automation options for less error in conversion.
After converting complete open your project in VS and disable all warning and switch option explicit off and option strict off.
If error is still appears try to fix them manually.
Once you are able to compile your project try to follow warning
Switch option explicit on and option strict on and follow any errors appears