Question

I want to create a List in an ActiveX component project in Visual Basic 6.0. Then I will get

the list from a c# project.

Thanks

Answer 1

With c#, you can create your own controls. You have different possibilities to do that.

1. Derive as class from System.Windows.Forms.Control and add your functionality. This is the most flexible, however most complicated approach.
2. Derive as class from an existing control which comes close to what you want to do and adapt it (e.g. by overriding OnPaint).
3. Add a UserControl to your project. You can place other controls on a UserControl much like you place controls on a form.

You can do this in your main assembly (.exe); however, if you do this in a class library (.dll), then you can use it much like an ActiveX control. In .NET, you do not need the “magic” of an ActiveX control. Controls are just classes that derive from Control.

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I often derive my own controls from ListBox and override OnPaint in order to display the items in a different way, by adding icons, by using different colors or by displaying text on multiple lines.

This is an example of a ListBox that I customized this way

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EDIT:

Are you looking for an alternative to the Collection type of VB6? In C# or VB.NET you use collections of the System.Collections.Generic namespace. List<T> for lists and Dictionary<TKey,TValue> for storing key/value pairs.

Example of lists:

var list = new List<string>();
list.Add("Hello");
list.Add("World");

Console.WriteLine(list[0]); // ==> "Hello"
Console.WriteLine(list[1]); // ==> "World"

foreach (string s in list) {
    Console.WriteLine(s);
}
// Output:  Hello
//          World

Example of key value pairs:

var dict = new Dictionary<string,int>();
dict.Add("Sunday", 1);
dict.Add("Monday", 2);
dict.Add("Tuesday", 3);
dict.Add("Wednesday", 4);
dict.Add("Thursday", 5);
dict.Add("Friday", 6);
dict.Add("Saturday", 7);

Console.WriteLine(dict["Wednesday"]); // ==> 4

int daynum;
if (dict.TryGetValue("Christmas", out daynum)) {
    Console.WriteLine("Christmas has the day number {0}.", daynum);
} else {
    Console.WriteLine("Christmas is not a weekday.");
}

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EDIT:

In order to use an ActiveX created with VB6 in .NET, you need the command line utility TlbImp provided in the .NET SDK. Call it like this

    tlbimp MyActiveX.dll /out:MyCsharp.dll

Then you can use MyCsharp.dll like any other .NET dll. See C# and ActiveX DLLs by Anand Narayanaswamy.