The following code implements a simple derived control with a public property called "MyProp". This property has a drop-down list with valid values:

using System;

using System.Collections.Generic;

using System.Text;

using System.Windows.Forms;

using System.ComponentModel;

using System.Collections;

namespace DefaultValuesTest2 {

public class MyTypeConv: TypeConverter {

public override bool GetStandardValuesSupported(ITypeDescriptorContext context) {

return true;

public override bool GetStandardValuesExclusive(ITypeDescriptorContext context) {

return true;

public override StandardValuesCollection GetStandardValues(ITypeDescriptorContext context) {

ArrayList list = new ArrayList(10);

list.Add("Name1");

list.Add("Name2");

list.Add("Name3");

return new StandardValuesCollection(list);

public class DefaultValLabel: Label {

private string _myProp;

[TypeConverter(typeof(MyTypeConv))]

public string MyProp {

get { return _myProp; }

set { _myProp = value; }

This code works fine, i.e. ifI place a DefaultValLabel on a form, the property "MyProp" works as expected and shows a drop-down list with 3 entries.

However, if I now change the implementation of GetStandardValues, e.g. add some new entries into the drop-down list, these new entries are NOT shown in the Visual Studio Designer. Rebuilding the application does not help. The only thing, which helps, is closing Visual Studio and restarting it.

Am I doing something wrong in my code, or is the Visual Studio designer only calling GetStandardValues once and then caching the drop-down list?

Dear joeycalisay.

You are right.

I tried to change the code again, this time building the drop-down list like this:

No, actually the derived control is in the same project as the form, which I place the control on.

Normally, I would always put the controls into a different project, too.

I just put the form and the control into the same project in this case, to see, if it made a difference.

If I put the control and form into two different projects, the problem is the same.

I can rebuild the whole solution or rebuild both projects independently - nothing helps.

Closing all windows in VS doesn't help.

Even closing the solution and reopening it, does not help.

I really have to close Visual Studio and restart it, to get the new drop down list in the designer.

Now, I have tried to change the implementation of GetStandardValues, building the list like this:

list.Add(DateTime.Now.ToString());

Dear joeycalisay.

You are right.

I tried to change the code again, this time building the drop-down list like this: