Access additional contextual data in EditValue UITypeEditor

Question

I am setting up a WinForms application. This app has a Form that contains a PropertyGrid . The object is assigned to the SelectedObject property, so the property grid displays the properties of the object.

The type of the assigned object has a property that carries an EditorAttribute with a UITypeEditor .

This implementation of UITypeEditor returns UITypeEditorEditStyle.Drop in its override of the GetEditStyle method. Its EditValue method displays a ListBox from which a value can be assigned to an instance property.

All is well good so far.

Now I have an additional requirement, which requires that the available items in the list be changed based on another state stored in the Form where the PropertyGrid located. I cannot figure out how to get this contextual information using the EditValue method.

There can be nothing in the context parameter, even if I try to apply it to more specific types. I also cannot decide how to add another service to retrieve from provider .

Any ideas?

Answer 1

I wonder if what you are trying to do is better than TypeConverter via GetStandardValues ? But in any case, both context.Instance and context.PropertyDescriptor seem to be populated by a quick test (for GetEditStyle and EditValue ):

 using System; using System.ComponentModel; using System.Drawing.Design; using System.Windows.Forms; class MyData { [Editor(typeof(MyEditor), typeof(UITypeEditor))] public string Bar { get; set; } public string[] Options { get; set; } } class MyEditor : UITypeEditor { public override UITypeEditorEditStyle GetEditStyle(ITypeDescriptorContext context) { // break point here; inspect context return UITypeEditorEditStyle.DropDown; } public override object EditValue(ITypeDescriptorContext context, IServiceProvider provider, object value) { // break point here; inspect context return base.EditValue(context, provider, value); } } class Program { [STAThread] static void Main() { Application.EnableVisualStyles(); Application.Run(new Form { Controls = { new PropertyGrid { Dock = DockStyle.Fill, SelectedObject = new MyData() } } }); } } 

Or as a type converter:

 using System; using System.ComponentModel; using System.Windows.Forms; class MyData { [TypeConverter(typeof(MyConverter))] public string Bar { get; set; } public string[] Options { get; set; } } class MyConverter : StringConverter { public override bool GetStandardValuesSupported(ITypeDescriptorContext context) { return true; } public override StandardValuesCollection GetStandardValues(ITypeDescriptorContext context) { MyData data = (MyData)context.Instance; if(data == null || data.Options == null) { return new StandardValuesCollection(new string[0]); } return new StandardValuesCollection(data.Options); } } class Program { [STAThread] static void Main() { Application.EnableVisualStyles(); Application.Run(new Form { Controls = { new PropertyGrid { Dock = DockStyle.Fill, SelectedObject = new MyData() } } }); } } 

Answer 2

I was in a similar situation, I wanted to inject an object into my own UITypeEditor constructor.

I followed Nicholas Cadillac's comment here , GIVE IT ALL CREDIT. It uses TypeDescriptionProvider.

Here is the complete set of code.

 class Foo { public Foo() { Bar = new Bar(); } public Bar Bar { get; set; } } class Bar { public string Value { get; set; } } class BarTypeDescriptionProvider : TypeDescriptionProvider { private TypeDescriptionProvider _baseProvider; string _extraParam; public BarTypeDescriptionProvider(Type t, string extraParam) { this._extraParam = extraParam; _baseProvider = TypeDescriptor.GetProvider(t); } public string ExtraParam { get { return _extraParam; } } public override ICustomTypeDescriptor GetTypeDescriptor(Type objectType, object instance) { return new BarTypeDescriptor(this, _baseProvider.GetTypeDescriptor(objectType, instance), objectType); } } class BarTypeDescriptor : CustomTypeDescriptor { private Type _objectType; private BarTypeDescriptionProvider _provider; public BarTypeDescriptor(BarTypeDescriptionProvider provider, ICustomTypeDescriptor descriptor, Type objectType): base(descriptor) { if (provider == null) throw new ArgumentNullException("provider"); if (descriptor == null) throw new ArgumentNullException("descriptor"); if (objectType == null) throw new ArgumentNullException("objectType"); _objectType = objectType; _provider = provider; } public override object GetEditor(Type editorBaseType) { return new BarEditor(_provider.ExtraParam); } } class BarEditor : UITypeEditor { private string _extraParam; public BarEditor(string x) : base() { _extraParam = x; } public override UITypeEditorEditStyle GetEditStyle(ITypeDescriptorContext context) { return UITypeEditorEditStyle.Modal; } public override object EditValue(ITypeDescriptorContext context, IServiceProvider provider, object value) { MessageBox.Show(_extraParam); return base.EditValue(context, provider, value); } } public partial class Form1 : Form { public Form1() { InitializeComponent(); string extraParam = "Extra param from main form"; TypeDescriptor.AddProvider(new BarTypeDescriptionProvider(typeof(Bar), extraParam), typeof(Bar)); this.propertyGrid1.SelectedObject = new Foo(); } } 

Michael

Answer 3

In an overridden method, EditValue context.Container will provide the object to which the editor belongs. The context.Container.Components property will display all controls that include the form and all its children.