C# Property for a list of classes

Question

I'm trying to use the property grid in the designer for Visual Studio.

I have a list of classes that I want the developer to be able to add to at design time so that the user can have access to extra features.

Here is some example code of what I have in the code already. The problem is when the developer goes to the design mode he can only see that there are x number of values in the list, but is unable to see any of the details. When trying to add a new item to the list the user is presented with an error.

Constructor on type 'EditorTextBox+SyntaxRegex' not found.

Now the code:

private List<SyntaxRegex> _syntaxRegexList = new List<SyntaxRegex>();
public class SyntaxRegex
{
   public string title;
   public string regex;
   public Color color;
}
Public List<SyntaxRegex> SyntaxRegexList
{
   get{_syntaxRegexList = value;}
   set{return _regexList;}
}

Answer 1

You need to add type converters / editors; a good start would be to add:

[TypeConverter(typeof(ExpandableObjectConverter))]

above each class definition. For example, the following works fine (note I changed to properties, removed the list setter, etc):

[TypeConverter(typeof(ExpandableObjectConverter))]
class Foo {
    private List<SyntaxRegex> _syntaxRegexList = new List<SyntaxRegex>();
    [TypeConverter(typeof(ExpandableObjectConverter))]
    public class SyntaxRegex
    {
       public override string ToString() {
           return string.IsNullOrEmpty(Title) ? "(no title)" : Title;
       }
       public string Title { get; set; }
       public string Regex { get; set; }
       public Color Color { get; set; }
    }
    [DisplayName("Patterns")]
    public List<SyntaxRegex> SyntaxRegexList
    {
        get { return _syntaxRegexList; }
    }
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.Run(new Form
        {
            Controls =
            {
                new PropertyGrid { 
                    Dock = DockStyle.Fill,
                    SelectedObject = new Foo()
                }
            }
        });
    }
}

The specific error message also makes me wonder if your actual type is public with a public parameterless constructor (the fact that it doesn't compile makes me suspect you haven't posted the actual code...)