Add Custom Properties to a PropertyGrid

• Download VB.NET demo project v1.03 - 188 Kb
• Download VB.NET source code v1.03 - 45.9 Kb
• Download C# version (source code and demo project) v1.02 - 170 Kb
• Download VB.NET 2003 version (source code only) v0.98 - 31.4 Kb

Introduction

For my last project, I looked at the PropertyGrid control that has a very nice look and feel. Immediately, I noticed how difficult it was to use it. Looking over the Internet, I found lots of people wishing for something easier to use, like the TreeView or the ListView. So I started developing an extended version of the PropertyGrid that includes an Item collection.

Using the Code

The control is made of three basic classes:

• Class CustomProperty, that represents a single property.
• Class CustomPropertyDescriptor, that is used internally by the PropertyGrid to retrieve property attributes.
• Class CustomPropertyCollection, that represents a collection of CustomPropertys.

In the end, we have the control PropertyGridEx that inherits from PropertyGrid and exposes an Item collection. To use the component, add it to the Toolbox and then to your form. Compared to the classic PropertyGrid, we have a new property to set, called ShowCustomProperties.

The property must be set to True, or the component will have the same behavior as the classic PropertyGrid.

The Item Collection

We are now ready to fill our custom properties.

With Properties
    .Item.Clear()
    .Item.Add("My String", "My Value", False, _
              "Simple type", "This is a string", True)
    .Item.Add("My Integer", 100, False, "Simple type", _
              "This is an integer", True)
    .Item.Add("My Double", 10.4, False, "Simple type", _
              "This is a double", True)
    .Item.Add("My Font", New Font("Arial", 9), False, _
              "Classes", "This is a font class", True)
    .Item.Add("My Color", New Color(), False, _
              "Classes", "This is a color class", True)
    .Item.Add("My Point", New Point(10, 10), False, _
              "Classes", "This is point class", True)
    .Refresh()
End With

The CustomProperty class exposes several properties that you can use to personalize your PropertyGrid:

• Name, a string representing the property name;
• Value, an object representing the value of the property;
• IsReadOnly, a boolean that indicates if the property is editable or not;
• Category, a string that represents the category in which the property is shown;
• Description, a string that represents the description of the property, shown at the bottom of the component;
• Visible, a boolean that indicates if the property is shown or not;

Finally, remember to Refresh the PropertyGrid after any modification to the collection.

The Filename Editor

It is also possible to create a CustomProperty that shows a dialog to modify a filename. The trick is achieved by the class UIFilenameEditor that inherits from System.Drawing.Design.UITypeEditor. You can create a property, with the well known FileDialog as a Type Editor, in the following way:

With Properties   
    .Clear
    .Item.Add("Filename", "", False, "Misc", "", True)
    .Item(.Item.Count - 1).UseFileNameEditor = True
    .Item(.Item.Count - 1).FileNameDialogType _
                         = FileDialogType.LoadFileDialog
    .Item(.Item.Count - 1).FileNameFilter = _
         "Text files (*.txt)|*.txt|All files (*.*)|*.*"
    .Refresh()
End With

Following is the resulting PropertyGrid. Please notice the Ellipsis symbol beside the value of the property, to access the UIFilenameEditor.

Custom Choices Type Converter

It's a very commonly requested feature to have a list of values from which the user can choose, while editing a property. To implement a dropdown list, do the following:

Dim Languages As String() = New String() {"English", _
                                          "Italian", _
                                          "Spanish", _
                                          "Dutch"}
With Properties   
    .Clear
    .Item.Add("Language", "", False, "Misc", "")
    .Item(.Item.Count - 1).Choices _
                         = New CustomChoices(Languages, True)
    .Refresh()
End With

You can use arrays of String, Integer, Double and Object to initialize the Choices property. Following is the resulting PropertyGrid initialized with an array of Strings.

Enumerations

Most of the times, developers have enumerations declared in their code. The component automatically shows a dropdown list with the values from the Enum.

Public Enum MyEnum
    FirstEntry
    SecondEntry
    ThirdEntry
End Enum

With Properties 
    .Clear
    .Item.Add("Enum", MyEnum.FirstEntry, False, "Misc")
    .Refresh()
End With

Following is the resulting PropertyGrid.

Expandable Object Converter

Using this TypeConverter, it is possible to expand nested properties. Here is an example that shows the application settings.

With Properties 
    .Clear
    .Item.Add("My settings", My.MySettings.Default, False, "Misc")
    .Item(.Item.Count - 1).IsBrowsable = True
    .Item(.Item.Count - 1).BrowsableLabelStyle = _
                           BrowsableTypeConverter.LabelStyle.lsEllipsis
    .Refresh()
End With

Following is the resulting PropertyGrid.

Password fields

Using masked fields, it is possible to hide the value of a property. The result is produced by the attribute PasswordPropertyTextAttribute, new to the .NET Framework v2.0. Here is an example on how to use it.

With Properties 
    .Clear
    .Item.Add("My Password", "password", False)
    .Item(.Item.Count - 1).IsPassword = True
    .Refresh()
End With

Following is the resulting PropertyGrid.

Dynamic property binding

Using PropertyGridEx, it is possible to bind object properties to the component. This is done by a method of the collection that accepts a value argument by reference. In this way, it is possible to freely mix reference type and value type properties. The following example binds the AutosizeProperties and the DrawFlatToolbar property of the grid.

Any modification to the value of these properties is automatically reflected into the object they belong to.

With Properties 
    .Clear
    .Item.Add("Autosize properties", Properties, "AutoSizeProperties", False, _
              "Dynamic Properties", "This is a dynamic bound property", True)
    .Item.Add("Draw flat toolbar", Properties, "DrawFlatToolbar", False, _
              "Dynamic Properties", "This is a dynamic bound property", True)
    .Refresh()
End With

Following is the resulting PropertyGrid.

Multiple object properties

One more feature provided with this control is the ability of editing multiple object properties at the same time. This is done by a collection of objects attached to the SelectedObjects property of the base component. The behavior is that the grid only displays the properties that are common to all the objects that are in the array. To activate the multiple objects functionality, the property of the grid ShowCustomPropertiesSet must be set to True.

With Properties
    .ShowCustomPropertiesSet = True
    .ItemSet.Clear()

    .ItemSet.Add()
    .ItemSet(0).Add("My Point", New Point(10, 10), False, "Appearance")
    .ItemSet(0).Add("My Date", New Date(2006, 1, 1), False, "Appearance")

    .ItemSet.Add()
    .ItemSet(1).Add("My Point", New Point(10, 10), False, "Appearance")
    .ItemSet(1).Add("My Date", New Date(2007, 1, 1), False, "Appearance")
    .ItemSet(1).Add("My Color", New Color(), False, "Appearance")

    .Refresh()
End With

Following is the resulting PropertyGrid.

Databinding of a Property to a Datasource

The databinding of a single property to a data-source is the latest addition to this component. The wrapper created accepts for a CustomProperty, three members:

• Datasource, the datasource to bind to.
• DisplayMember (optional), the field used to bind the list shown in the dropdown control.
• ValueMember (optional), the field used to bind the value returned by the CustomProperty.

The CustomProperty will return the following values:

• Value, that represents the value shown as System.String.
• SelectedItem, that represents the object selected as System.Object.
• SelectedValue, that represents the value selected as System.Object.

The following example creates three properties that bind a DataTable, an array of Objects, and an array of Strings.

With Properties
    .Item.Clear()
    .Item.Add("Datatable", "", False, "Databinding", _
              "This is a UITypeEditor that implement a listbox", True)

    .Item(.Item.Count - 1).ValueMember = "book_Id"
    .Item(.Item.Count - 1).DisplayMember = "title"      
    .Item(.Item.Count - 1).Datasource = LookupTable

    .Item.Add("Array of objects", ListValues(2).Text, False, "Databinding", _
              "This is a UITypeEditor that implement a listbox", True)

    .Item(.Item.Count - 1).ValueMember = "Value"
    .Item(.Item.Count - 1).DisplayMember = "Text"
    .Item(.Item.Count - 1).Datasource = ListValues   

    .Item.Add("Array of strings", Languages(1), False, "Databinding", _
              "This is a UITypeEditor that implement a listbox", True)

    .Item(.Item.Count - 1).Datasource = Languages    
    .Refresh()
End With

Please notice that the result is very different from the one achieved by using the "Custom Choices" functionality, that uses a TypeConverter. The databinding feature uses a UITypeConverter that implements a ListBox control.

Following is the resulting PropertyGrid.

Custom Event Editor

Using PropertyGridEx, it is possible to bind the 3-dots button used in Modal editors with a custom event handler. This is done by a method of the CustomProperty that accepts a Delegate as argument. The following is an example:

With Properties 
    .Clear
    .Item.Add("My Custom Event", "(Click me)", False, "Misc", _
              "The component accept custom event handler.", True) 
    .Item(.Item.Count - 1).OnClick = AddressOf Me.CustomEventItem_OnClick     
    .Refresh()
End With

The event will be handled by this function:

Private Function CustomEventItem_OnClick(ByVal sender As Object, _
                                         ByVal e As EventArgs) As Object 
    MsgBox("You clicked on property '" & sender.CustomProperty.Name & "'", _
           MsgBoxStyle.Information, _
           "Custom Events as UITypeEditor") 
    Return "(Click me again)" 
End Function 

Please notice that the result value of the function will be the new value of the property. Following is the resulting PropertyGrid.

Add some style to the control

Looking on Internet and on CodeProject, I found a lot of articles regarding this component. Unfortunately, I had to merge everything together to have an easier PropertyGrid to use. In this section, you'll find small features I've found and added in this project.

• AutoSizeProperties - Move automatically the splitter to better fit all the properties shown.
• MoveSplitterTo - Move the splitter as indicated by the user in the parameter.
• DocComment - Expose the comments area as a control.
• DrawFlatToolbar - Draw a flat toolbar or a VS like toolbar.

Please notice that the last property switches the drawing of the toolbar within a Professional Renderer with custom colors and a System Renderer.

Final Notes

I hope that you find this article useful. If you found this article stupid, annoying, incorrect, etc., express this fact by rating the article as you see fit.

Credits

Thanks to Pascal Higelin for providing the Property Binding feature and the C# version.
Thanks to Suresh Kavan, for the idea and the test case for the data-binding feature.

References

• Getting the Most out of the PropertyGrid Control
• Add Item to PropertyGrid at Runtime
• Bending the .NET PropertyGrid to Your Will
• Handy Type Editors: Customizable Filename Editor
• Handy Type Editors: Universal Dropdown Editor

History

• 22^nd August 2006
  • Added XML Editor sample.
• 31^st May 2006
  • Added custom event editor.
  • Added DocComment interface.
• 5^th May 2006
  • Added serialization.
  • Added property databinding.
  • Article updated.
• 28^th April 2006
  • Added C# version.
  • Added dynamic property binding.
  • Added multiple objects feature.
• 10^th April 2006
  • Added password property and improved ToolStrip look.
  • Added expandable object converter.
  • Added custom choices type converter.
  • Added file name editor.
• 31^st March 2006 – First submission.