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Code Conversion

This section provides some transformation that we apply so that some elements will be upgraded as you need it.

Last updated 8 months ago

1. ActiveX

1.1. .NET Assemblies with COM Visible

This option will generate special attributes for the converted classes and their members in order to keep the resulting assemblies exposed through a COM interface.

This feature enables the resulting .NET components to be called from other non-managed components or applications via COM.

General Description:

The VBUC converts Visual Basic 6 ActiveX binaries to .NET assemblies. By default, the resulting assemblies can be used only from managed code. This option should be selected to generate the .NET attributes required to expose these assemblies as COM Objects if it’s necessary to use them from non-managed code.

In addition to the “COMVisible” attribute on the class members, the resulting project is also marked as COM Visible.

Original VB6 code:

Code declared in an Activex EXE:

Module1.bas

Public myVar As String

Customer.cls

Attribute VB_Name = "Customer"

Private g_TheNumber As Integer

Public Property Let TheNumber(ByVal new_value As Integer)
   g_TheNumber = new_value
End Property

Public Property Get TheNumber() As Integer
   TheNumber = g_TheNumber
End Property

Code located in the main application that uses the Activex EXE:

Private m_Customer1 As ExeBillingObjects.Customer
Private m_Customer2 As ExeBillingObjects.Customer

Private Sub Form_Load()
   Set m_Customer1 = New ExeBillingObjects.Customer
   Set m_Customer2 = New ExeBillingObjects.Customer
End Sub

Private Sub cmdGet_Click()
   txtTheNumber.Text = m_Customer1.TheNumber
End Sub

C# code:

Code declared in an Activex EXE:

Module1.cs

internal static class Module1
{
	public static string myVar = "";
}

Customer.cs

[ComVisible(true)][ProgId("ExeBillingObjects.Customer")][ClassInterface(ClassInterfaceType.AutoDual)]
public class Customer
{
	public int TheNumber
	{
		get
		{
			return Module1.g_TheNumber;
		}
		set
		{
			Module1.g_TheNumber = value;
		}
	}	
}

Code located in the main application that uses the Activex EXE:

private ExeBillingObjects.Customer m_Customer1 = null;
private ExeBillingObjects.Customer m_Customer2 = null;
			
private void  cmdSet_Click( Object eventSender,  EventArgs eventArgs)
{
	m_Customer1.TheNumber = Convert.ToInt32(Double.Parse(txtTheNumber.Text));
	txtTheNumber.Text = "";
}

private void  Form1_Load( Object eventSender,  EventArgs eventArgs)
{
	m_Customer1 = new ExeBillingObjects.Customer();
	m_Customer2 = new ExeBillingObjects.Customer();
}

VB.NET code:

Code declared in an Activex EXE:

Module1.vb

Module Module1
	Public myVar As String = ""
End Module

Customer.vb

<ComVisible(True)> _
<ProgId("ExeBillingObjects.Customer")> _
<ClassInterface(ClassInterfaceType.AutoDual)> _
Public Class Customer
	Public Property TheNumber() As Integer
		Get
			Return g_TheNumber
		End Get
		Set(ByVal Value As Integer)
			g_TheNumber = Value
		End Set
	End Property
End Class

Code located in the main application that uses the Activex EXE:

Private m_Customer1 As ExeBillingObjects.Customer
Private m_Customer2 As ExeBillingObjects.Customer

Private Sub cmdGet_Click(ByVal eventSender As Object, ByVal eventArgs As EventArgs) Handles cmdGet.Click
	txtTheNumber.Text = CStr(m_Customer1.TheNumber)
End Sub

Private Sub Form1_Load(ByVal eventSender As Object, ByVal eventArgs As EventArgs) Handles MyBase.Load
	m_Customer1 = New ExeBillingObjects.Customer()
	m_Customer2 = New ExeBillingObjects.Customer()
End Sub

1.2. Out process and Application

This optional feature enables the conversion of ActiveX DLLs and EXEs (with global variables in a .bas module) via a helper class (ComponentClassHelper) that controls the instantiation of the generated classes.

ActiveX EXEs are converted to out-of-process .NET EXEs.
ActiveX DLLs are converted to .NET class libraries using application domains.
Component instantiation is performed using helper classes. With this approach most of the ActiveX functionality is replicated in the converted code.

General Description:

The VBUC converts Visual Basic 6 ActiveX EXEs to .NET EXE projects (out-of-process) and ActiveX DLLs to .NET assemblies (class library projects).

One of the main differences between Visual Basic 6 ActiveX binaries and .NET assemblies is how the components are instantiated and how their initialization determines its lifetime behavior.

When this feature is active, a helper class is used to replicate the following ActiveX instantiation types:

Private
PublicNotCreatable
SingleUse
GlobalSingleUse
MultiUse
GlobalMultiUse

Original VB6 code:

Code declared in an Activex EXE:

Module1.bas

Public myVar As String

Customer.cls

Attribute VB_Name = "Customer"

Private g_TheNumber As Integer

Public Property Let TheNumber(ByVal new_value As Integer)
   g_TheNumber = new_value
End Property

Public Property Get TheNumber() As Integer
   TheNumber = g_TheNumber
End Property

Code located in the main application that uses the Activex EXE:

Private m_Customer1 As ExeBillingObjects.Customer
Private m_Customer2 As ExeBillingObjects.Customer

Private Sub Form_Load()
   Set m_Customer1 = New ExeBillingObjects.Customer
   Set m_Customer2 = New ExeBillingObjects.Customer
End Sub

Private Sub cmdGet_Click()
   txtTheNumber.Text = m_Customer1.TheNumber
End Sub

C# code:

Code declared in an Activex EXE:

Module1.cs

internal static class Module1
{
	public static string myVar = "";
	internal static void InitGlobalVars()
	{
		myVar = "";
	}
}

Customer.cs

public class Customer : UpgradeHelpers.Activex.ComponentClassHelper
{
	public int TheNumber
	{
		get
		{
			return g_TheNumber;
		}
		set
		{
			g_TheNumber = value;
		}
	}	
}

Code located in the main application that uses the Activex EXE:

private ExeBillingObjects.Customer m_Customer1 = null;
private ExeBillingObjects.Customer m_Customer2 = null;
			
private void cmdGet_Click( Object eventSender,  EventArgs eventArgs)
{
	txtTheNumber.Text = Convert.ToString(m_Customer1.TheNumber);
}

private void Form1_Load( Object eventSender,  EventArgs eventArgs)
{
	m_Customer1 = ExeBillingObjects.ExeBillingObjectsFactory.Create <ExeBillingObjects.Customer>(m_Customer1);
	m_Customer2 = ExeBillingObjects.ExeBillingObjectsFactory.Create <ExeBillingObjects.Customer>(m_Customer2);

VB.NET code:

Code declared in an Activex EXE:

Module1.vb

Module Module1
	Public myVar As String = ""
	Public Sub InitGlobalVars()
		myVar = ""
	End Sub
End Module

Customer.vb

Public Class Customer Inherits UpgradeHelpers.Activex.ComponentClassHelper
	Public Property TheNumber() As Integer
		Get
			Return g_TheNumber
		End Get
		Set(ByVal Value As Integer)
			g_TheNumber = Value
		End Set
	End Property
End Class

Code located in the main application that uses the Activex EXE:

Private m_Customer1 As ExeBillingObjects.Customer
Private m_Customer2 As ExeBillingObjects.Customer
	
Private Sub cmdGet_Click(ByVal eventSender As Object, ByVal eventArgs As EventArgs) Handles cmdGet.Click
	txtTheNumber.Text = CStr(m_Customer1.TheNumber)
End Sub
	
Private Sub Form1_Load(ByVal eventSender As Object, ByVal eventArgs As EventArgs) Handles MyBase.Load
	m_Customer1 = ExeBillingObjects.ExeBillingObjectsFactory.Create(Of ExeBillingObjects.Customer)(m_Customer1)
	m_Customer2 = ExeBillingObjects.ExeBillingObjectsFactory.Create(Of ExeBillingObjects.Customer)(m_Customer2)
End Sub

1.3. Standard .NET Assemblies

This optional feature converts the ActiveX DLLs and EXEs to .NET class libraries (DLLs).

All ActiveX binaries are converted to native .NET assemblies (class libraries).
With this approach, the converted code can be used only from managed code and the different ActiveX instantiation models (e.g MultiUse, GlobalMultiuse, etc) won’t be supported.

General Description:

The VBUC converts Visual Basic 6 ActiveX EXEs and ActiveX DLLs to .NET class libraries (DLLs).

One of the main differences between Visual Basic 6 ActiveX binaries and .NET assemblies is how the components are instantiated and how their initialization determines its lifetime behavior.

With this option switched on, the code is converted to pure .NET code and the ActiveX instantiation models won’t be supported.

Original VB6 code:

Code declared in an Activex EXE:

Module1.bas

Public myVar As String

Customer.cls

Attribute VB_Name = "Customer"

Private g_TheNumber As Integer

Public Property Let TheNumber(ByVal new_value As Integer)
   g_TheNumber = new_value
End Property

Public Property Get TheNumber() As Integer
   TheNumber = g_TheNumber
End Property

Code located in the main application that uses the Activex EXE:

Private m_Customer1 As ExeBillingObjects.Customer
Private m_Customer2 As ExeBillingObjects.Customer

Private Sub Form_Load()
   Set m_Customer1 = New ExeBillingObjects.Customer
   Set m_Customer2 = New ExeBillingObjects.Customer
End Sub

Private Sub cmdGet_Click()
   txtTheNumber.Text = m_Customer1.TheNumber
End Sub

C# code:

Code declared in an Activex EXE:

Module1.cs

internal static class Module1
{
	public static string myVar = "";
}

Customer.cs

public class Customer
{
	public int TheNumber
	{
		get
		{
			return g_TheNumber;
		}
		set
		{
			g_TheNumber = value;
		}
	}	
}

Code located in the main application that uses the Activex EXE:

private ExeBillingObjects.Customer m_Customer1 = null;
private ExeBillingObjects.Customer m_Customer2 = null;
			
private void  cmdGet_Click( Object eventSender,  EventArgs eventArgs)
{
	txtTheNumber.Text = m_Customer1.TheNumber.ToString();
}
			
private void  Form1_Load( Object eventSender,  EventArgs eventArgs)
{
	m_Customer1 = new ExeBillingObjects.Customer();
	m_Customer2 = new ExeBillingObjects.Customer();
}

VB.NET code:

Code declared in an Activex EXE:

Module1.vb

Module Module1
	Public myVar As String = ""
End Module

Customer.vb

Public Class Customer
	Public Property TheNumber() As Integer
		Get
			Return g_TheNumber
		End Get
		Set(ByVal Value As Integer)
			g_TheNumber = Value
		End Set
	End Property
End Class

Code located in the main application that uses the Activex EXE:

Private m_Customer1 As ExeBillingObjects.Customer
Private m_Customer2 As ExeBillingObjects.Customer

Private Sub cmdGet_Click(ByVal eventSender As Object, ByVal eventArgs As EventArgs) Handles cmdGet.Click
	txtTheNumber.Text = CStr(m_Customer1.TheNumber)
End Sub

Private Sub Form1_Load(ByVal eventSender As Object, ByVal eventArgs As EventArgs) Handles MyBase.Load
	m_Customer1 = New ExeBillingObjects.Customer()
	m_Customer2 = New ExeBillingObjects.Customer()
End Sub

2. Comment Out Dead Code

2.1. On

Private methods that are not referenced will be commented out.

Original VB6 code:

Public Sub PublicMethod()
	Call CalledPrivateMethod
End Sub

Private Sub CalledPrivateMethod()
	MsgBox "This method is called."
End Sub

Private Sub UncalledPrivateMethod()
	MsgBox "This method is not called."
End Sub

C# code:

public void PublicMethod()
{
	CalledPrivateMethod();
}

private void CalledPrivateMethod()
{
	MessageBox.Show("This method is called.", AssemblyHelper.GetTitle(System.Reflection.Assembly.GetExecutingAssembly()));
}

//UPGRADE_NOTE: (7001) The following declaration (UncalledPrivateMethod) seems to be dead code
//private void UncalledPrivateMethod()
//{
	//MessageBox.Show("This method is not called.", AssemblyHelper.GetTitle(System.Reflection.Assembly.GetExecutingAssembly()));
//}

VB.NET code:

Public Sub PublicMethod()
	CalledPrivateMethod()
End Sub

Private Sub CalledPrivateMethod()
	MessageBox.Show("This method is called.", My.Application.Info.Title)
End Sub

'UPGRADE_NOTE: (7001) The following declaration (UncalledPrivateMethod) seems to be dead code'
'Private Sub UncalledPrivateMethod()'
	'MessageBox.Show("This method is not called.", My.Application.Info.Title)'
'End Sub'

2.1. Off

This feature will be turned off and no changes pertaining to this feature will be made.

Original VB6 code:

Public Sub PublicMethod()
	Call CalledPrivateMethod
End Sub

Private Sub CalledPrivateMethod()
	MsgBox "This method is called."
End Sub

Private Sub UncalledPrivateMethod()
	MsgBox "This method is not called."
End Sub

C# code:

public void PublicMethod()
{
	CalledPrivateMethod();
}

private void CalledPrivateMethod()
{
	MessageBox.Show("This method is called.", AssemblyHelper.GetTitle(System.Reflection.Assembly.GetExecutingAssembly()));
}

private void UncalledPrivateMethod()
{
	MessageBox.Show("This method is not called.", AssemblyHelper.GetTitle(System.Reflection.Assembly.GetExecutingAssembly()));
}

VB.NET code:

Public Sub PublicMethod()
	CalledPrivateMethod()
End Sub

Private Sub CalledPrivateMethod()
	MessageBox.Show("This method is called.", My.Application.Info.Title)
End Sub

Private Sub UncalledPrivateMethod()
	MessageBox.Show("This method is not called.", My.Application.Info.Title)
End Sub

3. Default Property Resolution

3.1. Static code analysis and helpers classes

By switching this feature on, the majority of default property cases that could not be resolved with a static code analysis are managed at runtime by the use of a helper class.

Manages special cases of default properties at runtime by using a helper class.
Increases the automation ratio and reduces the manual effort required to achieve functional equivalence.

General Description:

The Visual Basic Upgrade Companion uses a powerful static code analyzer to determine the correct type for each object. By having the correct type for each object, the VBUC is able to determine its default property and expand this property in the converted code.

However, there are some cases where it’s not possible to determine the type of an object by using this technique. For these scenarios, the VBUC provides a helper class that is able to determine the type of these objects at runtime and get or set their default property.

In the following example, the variable ctl is used to iterate over a different type of controls. Each of these controls has different default properties, thus, during runtime, the default property of ctl will change. If this example is converted using this option, the helper class will determine the type of each use of the ctl variable at runtime and will get the appropriate default property for each instance.

Original VB6 code:

Dim s As String
'Display the default property of controls of a Form'
For Each ctl In Me.Controls
	s = ctl
	MsgBox s
Next ctl
'Display the default property of TextBox'
MsgBox Me.TextBox1

C# code:

string s = String.Empty;
//Display the default property of controls of a Form
foreach (Control ctl in ContainerHelper.Controls(this))
{
	s = ReflectionHelper.GetPrimitiveValue(ctl).ToString(); 
	MessageBox.Show(s, Application.ProductName);
}
//Display the default property of TextBox
MessageBox.Show(this.TextBox1.Text, Application.ProductName);

VB.NET code:

Dim s As String = ""
'Display the default property of controls of a Form'
For Each ctl As Control In ContainerHelper.Controls(Me)
	s = ReflectionHelper.GetPrimitiveValue(ctl).ToString()
	MessageBox.Show(s, Application.ProductName)
Next ctl
'Display the default property of TextBox'
MessageBox.Show(Me.TextBox1.Text, Application.ProductName)

3.2. Static code analysis only

By switching this feature on, the VBUC will use a powerful static code analysis process to determine the correct type for each object and expands its default property.

Expands the default properties by using only static code analysis.
There are some cases where it’s not possible to determine the type of an object by using static code analysis and it may require manual intervention to achieve functional equivalence.

General Description:

The Visual Basic Upgrade Companion (VBUC) uses a static code analysis process to infer/determine the correct type for each object. By having the correct type of each object, the VBUC can determine the default property of the object and expand this property in the converted code.

However, there some cases where it is not possible to determine the type of an object by using a static code analysis. For these cases manual changes are required to achieve functional equivalence.

Original VB6 code:

Dim s As String
'Display the default property of controls of a Form'
For Each ctl In Me.Controls
	s = ctl
	MsgBox s
Next ctl
'Display the default property of TextBox'
MsgBox Me.TextBox1

C# code:

string s = String.Empty;
//Display the default property of controls of a Form
foreach (Control ctl in ContainerHelper.Controls(this))
{
	//UPGRADE_WARNING: (1068) ctl of type VB.Control is being forced to string
	s = ctl.ToString();
	MessageBox.Show(s, Application.ProductName);
}
//Display the default property of TextBox
MessageBox.Show(this.TextBox1.Text, Application.ProductName);

VB.NET code:

Dim s As String = ""
'Display the default property of controls of a Form'
For Each ctl As Control In ContainerHelper.Controls(Me)
	'UPGRADE_WARNING: (1068) ctl of type VB.Control is being forced to String.'
	s = ctl.ToString()
	MessageBox.Show(s, Application.ProductName)
Next ctl
'Display the default property of TextBox'
MessageBox.Show(Me.TextBox1.Text, Application.ProductName)

4. Error Handling

4.1. Leave on Error Statements (VB.NET Only)

By choosing this option the VBUC will generate .NET source code that employs the “On Error” statements just like the Visual Basic 6 code.

This option increases the automation and reduces the manual effort required to get functional equivalence.
This feature is optional while upgrading to Visual Basic .NET but is not available for C#.

General Description:

The “On Error Go To” and “On Error Resume Next” error handling statements present in the Visual Basic 6 code will remain the same on the Visual Basic .NET output code. This feature removes the need for manual changes to bring the error handling statements to functional equivalence since it will be used the same in the upgraded code.

Original VB6 code:

Public Sub OnErrorGotoLabelMethod(arg As String)
    On Error GoTo errHnd
        Dim s As Integer
        s = CInt(arg)
        Foo s
        Exit Sub
errHnd:
        MsgBox "Invalid Argument"
End Sub

Public Sub OnErrorResumeNextMethod(arg As String)
On Error Resume Next
    MsgBox arg
    MsgBox CInt(arg)
    MsgBox "This line will be executed allways"
    
    If Err.Number <> 0 Then
        'This code should be executed if there were any error(s)'
        MsgBox "OnErrorResumeNextMethod reached the last statement"
        MsgBox "OnErrorResumeNextMethod reached the last statement"
        MsgBox "OnErrorResumeNextMethod reached the last statement"
    End If
End Sub

VB.NET code:

Public Sub OnErrorGotoLabelMethod(ByVal arg As String)
	On Error GoTo errHnd
	Dim s As Integer
	s = CInt(arg)
	Foo(s)
	Exit Sub
errHnd:
	MessageBox.Show("Invalid Argument", My.Application.Info.Title)
End Sub

Public Sub OnErrorResumeNextMethod(ByVal arg As String)
	On Error Resume Next
	MessageBox.Show(arg, My.Application.Info.Title)
	MessageBox.Show(CStr(CInt(arg)), My.Application.Info.Title)
	MessageBox.Show("This line will be executed allways", My.Application.Info.Title)

	If Information.Err().Number <> 0 Then
		'This code should be executed if there were any error(s)'
		MessageBox.Show("OnErrorResumeNextMethod reached the last statement", My.Application.Info.Title)
		MessageBox.Show("OnErrorResumeNextMethod reached the last statement", My.Application.Info.Title)
		MessageBox.Show("OnErrorResumeNextMethod reached the last statement", My.Application.Info.Title)
	End If
End Sub

4.2. Convert to Try-Catch

The most common occurrences of error handling patterns will be automatically upgraded to Try-Catch blocks using this feature. It covers a vast amount of On Error Goto patterns and very basic cases of On Error Resume Next.

This option generates more .NET-like code.
This feature is optional while upgrading to Visual Basic .NET but is compulsory for C# code generation.

General Description:

The Visual Basic Upgrade Companion analyzes the execution control of the Visual Basic 6 code detecting the “On Error GoTo” error handling patterns to generate .NET inherent Try-Catch blocks. When "On Error Resume Next" error handling patterns are found, they will be transformed to a basic Try-Catch block, which will have a different behavior. For the most common scenarios this transformation generates error-free pure .NET code out of the box. For more radical cases, the spaghetti-like error handling code found on Visual Basic 6 might require either some changes prior to the upgrade process or manual efforts once it is upgraded to .NET.

Original VB6 code:

Public Sub OnErrorGotoLabelMethod(arg As String)
    On Error GoTo errHnd
        Dim s As Integer
        s = CInt(arg)
        Foo s
        Exit Sub
errHnd:
        MsgBox "Invalid Argument"
End Sub

Public Sub OnErrorResumeNextMethod(arg As String)
On Error Resume Next
    MsgBox arg
    MsgBox CInt(arg)
    MsgBox "This line will be executed allways"
    
    If Err.Number <> 0 Then
        'This code should be executed if there were any error(s)'
        MsgBox "OnErrorResumeNextMethod reached the last statement"
        MsgBox "OnErrorResumeNextMethod reached the last statement"
        MsgBox "OnErrorResumeNextMethod reached the last statement"
    End If
End Sub

C# code:

public void OnErrorGotoLabelMethod(string arg)
{
	try
	{
		int s = 0;
		s = Convert.ToInt32(Double.Parse(arg));
		Foo(s);
	}
	catch
	{
		MessageBox.Show("Invalid Argument", AssemblyHelper.GetTitle(System.Reflection.Assembly.GetExecutingAssembly()));
	}
}

public void OnErrorResumeNextMethod(string arg)
{
	//UPGRADE_TODO: (1069) Error handling statement (On Error Resume Next) was converted to a pattern that might have a different behavior.
	try
	{
		MessageBox.Show(arg, AssemblyHelper.GetTitle(System.Reflection.Assembly.GetExecutingAssembly()));
		MessageBox.Show(Convert.ToInt32(Double.Parse(arg)).ToString(), AssemblyHelper.GetTitle(System.Reflection.Assembly.GetExecutingAssembly()));
		MessageBox.Show("This line will be executed allways", AssemblyHelper.GetTitle(System.Reflection.Assembly.GetExecutingAssembly()));

		//UPGRADE_WARNING: (2081) Err.Number has a new behavior.
		if (Information.Err().Number != 0)
		{
			//This code should be executed if there were any error(s)
			MessageBox.Show("OnErrorResumeNextMethod reached the last statement", AssemblyHelper.GetTitle(System.Reflection.Assembly.GetExecutingAssembly()));
			MessageBox.Show("OnErrorResumeNextMethod reached the last statement", AssemblyHelper.GetTitle(System.Reflection.Assembly.GetExecutingAssembly()));
			MessageBox.Show("OnErrorResumeNextMethod reached the last statement", AssemblyHelper.GetTitle(System.Reflection.Assembly.GetExecutingAssembly()));
		}
	}
	catch (Exception exc)
	{
		NotUpgradedHelper.NotifyNotUpgradedElement("Resume in On-Error-Resume-Next Block");
	}
}

VB.NET code:

Public Sub OnErrorGotoLabelMethod(ByVal arg As String)
	Try
		Dim s As Integer
		s = CInt(arg)
		Foo(s)

	Catch
		MessageBox.Show("Invalid Argument", My.Application.Info.Title)
	End Try
End Sub

Public Sub OnErrorResumeNextMethod(ByVal arg As String)
	'UPGRADE_TODO: (1069) Error handling statement (On Error Resume Next) was converted to a pattern that might have a different behavior.'
	Try
		MessageBox.Show(