Using PropertyGrid Part-I

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Introduction

For my last project, I had a requirement where I can use PropertyGrid control. I tried to get information on that, from Microsoft and searching all over Internet, newsgroups, but I could find only a couple of articles from Microsoft. That's it, surprising, and not even a single example in VB.NET that compiles without errors and explains all in and outs of PropertyGrid control.

So, I decided to put all the information I collected, with fully functional working examples in VB.NET (which is my favorite) and let me tell you, it is the most complex control of all controls in VS.NET, yet very powerful and extremely useful, particularly in Custom Controls, and for Application Configuration settings. Visual Studio .NET property browser is also based upon the PropertyGrid.

Its so complex that I have to split this article into two parts. In this Part-I, I will explain how to use the basic properties and System resources, and in Part-II I will cover the advanced topic on using Custom Editors and User defined types.

Description

Open a new Windows application project using VB.NET. By default PropertyGrid is not visible in the Toolbox. So click on Customize Toolbox and add the PropertyGrid Control.

Adding the control, and dropping it on the Designer is pretty much the same like any other control. Fun starts after that. In order to use the PropertyGrid control, you have to provide a class as source to the PropertyGrid. Let's see a small example.

Imports System.ComponentModel
'''

<DefaultPropertyAttribute("Title")> _
Public Class SimpleProperties
    '''

    Private _Title As String
    Private _Show As Boolean
    Private _Number As Short
    '''

    <CategoryAttribute("Application"), _
       Browsable(True), _
       [ReadOnly](False), _
       BindableAttribute(False), _
       DefaultValueAttribute(""), _
       DesignOnly(False), _
       DescriptionAttribute("Enter Title for the application")> _
       Public Property Title() As String
           Get
               Return _Title
           End Get
           Set(ByVal Value As String)
               _Title = Value
           End Set
       End Property
    '''

    <CategoryAttribute("Application"), _
       Browsable(True), _
       [ReadOnly](False), _
       BindableAttribute(False), _
       DefaultValueAttribute("True"), _
       DesignOnly(False), _
       DescriptionAttribute("Show option")> _
       Public Property Show() As Boolean
           Get
               Return _Show
           End Get
           Set(ByVal Value As Boolean)
               _Show = Value
            End Set
       End Property
    '''

    <CategoryAttribute("Application"), _
       Browsable(True), _
       [ReadOnly](False), _
       BindableAttribute(False), _
       DefaultValueAttribute("0"), _
       DesignOnly(False), _
       DescriptionAttribute("Enter a number")> _
       Public Property Number() As Short
           Get
               Return _Number
           End Get
           Set(ByVal Value As Short)
               _Number = Value
           End Set
       End Property
    '''

End Class

To your form_load event add the following code:

PropertyGrid1.SelectedObject = New SimpleProperties()

Press F5 to run the project. Let's see the elements in the SimpleProperties.vb class

Then add the properties that you want to see in the PropertyGrid with right data types. Finally, assign the Class to the PropertyGrid's SelectedObject property. That's all we have to do. Rest is taken care by the PropertyGrid and you see the following output.

Let's add some System resources to the above class

Private _ApplicationSize As Size
Private _ApplicationLocation As Point
Private _ApplicationFont As System.Drawing.Font
Private _FontColor As System.Drawing.Color
Private _ApplicationIcon As System.Drawing.Icon
Private _ApplicationCursor As System.Windows.Forms.Cursor
Private _ApplicationLangugae As System.Globalization.CultureInfo
'''

<CategoryAttribute("Design"), DefaultValueAttribute(""), _
DescriptionAttribute("Enter Application size")> _
Public Property ApplicationSize() As Size
    Get
        Return _ApplicationSize
    End Get
    Set(ByVal Value As Size)
        _ApplicationSize = Value
    End Set
End Property

<CategoryAttribute("Design"), DefaultValueAttribute(""), _
DescriptionAttribute("Enter Application Location")> _
Public Property ApplicationLocation() As Point
   Get
        Return ApplicationLocation
    End Get
    Set(ByVal Value As Point)
        _ApplicationLocation = Value
    End Set
End Property

<CategoryAttribute("Design"), DefaultValueAttribute(""), _
DescriptionAttribute("Select font for the application")> _
Public Property ApplicationFont() As System.Drawing.Font
    Get
        Return _ApplicationFont
    End Get
    Set(ByVal Value As System.Drawing.Font)
        _ApplicationFont = Value
    End Set
End Property

<CategoryAttribute("Design"), DefaultValueAttribute(""), _
DescriptionAttribute("Select font color")> _
Public Property FontColor() As System.Drawing.Color
    Get
        Return _FontColor
    End Get
    Set(ByVal Value As System.Drawing.Color)
        _FontColor = Value
    End Set
End Property

<CategoryAttribute("Design"), DefaultValueAttribute(""), _
DescriptionAttribute("Select icon for application")> _
Public Property ApplicationIcon() As System.Drawing.Icon
    Get
        Return _ApplicationIcon
    End Get
    Set(ByVal Value As System.Drawing.Icon)
        _ApplicationIcon = Value
    End Set
End Property

<CategoryAttribute("Design"), DefaultValueAttribute(""), _
DescriptionAttribute("Select application's cursor")> _
Public Property ApplicationCursor() As System.Windows.Forms.Cursor
    Get
        Return _ApplicationCursor
    End Get
    Set(ByVal Value As System.Windows.Forms.Cursor)
        _ApplicationCursor = Value
    End Set
End Property

<CategoryAttribute("Design"), DefaultValueAttribute(""), _
DescriptionAttribute("Select User language")> _
Public Property ApplicationLangugae() As System.Globalization.CultureInfo
    Get
        Return _ApplicationLangugae
    End Get
    Set(ByVal Value As System.Globalization.CultureInfo)
        _ApplicationLangugae = Value
    End Set
End Property

Again, PropertyGrid automatically populates Enumerations as drop down list, and system structures as collapsible sub sections.

Adding custom dropdown list

Now let's add a custom dropdown list which shows all states. In order to add a custom dropdown list, create a class that inherits from System.ComponentModel.TypeConverter or any other class, that was derived from TypeConverter class that matches your datatype. (check for System.ComponentModel namespace for all available custom type convert classes) So, for our example we inherit from System.ComponentModel.StringConverter

Public Class StatesList : Inherits System.ComponentModel.StringConverter

Override the GetStandardValuesSupported method to indicate that this object supports a standard set of values.

Public Overloads Overrides Function _
    GetStandardValues(ByVal context As _
    System.ComponentModel.ITypeDescriptorContext) _
    As System.ComponentModel.TypeConverter.StandardValuesCollection
    
    Return New StandardValuesCollection(_States)
End Function

Override the GetStandardValues method and return a StandardValuesCollection filled with our custom list.

Dim _States As String() = New String() {"Alabama", "Alaska",_
             "Arizona", "Arkansas", _
            "California", "Colorado", "Connecticut", "Delaware",_
            "Florida", "Georgia", _
            "Hawaii", "Idaho", "Illinois", "Indiana", "Iowa", "Kansas", _
            "Kentucky", "Louisiana", "Maine", "Maryland", "Massachusetts", _
            "Michigan", "Minnesota", "Mississippi", "Missouri", "Montana", _
            "Nebraska", "Nevada", "New Hampshire", _
            "New Jersey", "New Mexico", _
            "New York", "North Carolina", "North Dakota",_
            "Ohio", "Oklahoma", _
            "Oregon", "Pennsylvania", "Rhode Island", "South Carolina", _
            "South Dakota", "Tennessee", "Texas", "Utah",_
            "Vermont", "Virginia",_
            "Washington", "West Virginia", "Wisconsin", "Wyoming"}

Public Overloads Overrides Function _
    GetStandardValues(ByVal context As _
    System.ComponentModel.ITypeDescriptorContext) _
    As System.ComponentModel.TypeConverter.StandardValuesCollection

    Return New StandardValuesCollection(_States)
End Function

Finally override the GetStandardValuesExclusive method. When set to false, it changes the dropdown list to Combo box (editable). If set to true, then its a simple list box (Read only).

Public Overloads Overrides Function _
    GetStandardValuesExclusive(ByVal context _
    As System.ComponentModel.ITypeDescriptorContext) _
    As Boolean
    
    Return True
End Function

Then apply the statesList class to the property by using the TypeConverterAttribute. Let's add a State property to the above example.

Private _State As String
'''

<TypeConverter(GetType(StatesList)), _
    CategoryAttribute("Custom List"), DefaultValueAttribute(""), _
    DescriptionAttribute("Select a state from the list")> _
    Public Property State() As String
    
    Get
        Return _State
    End Get
    Set(ByVal Value As String)
        _State = Value
    End Set
End Property

and here is the output.

Displaying custom data types with expandable properties

.NET framework data types like Size, Point when used in PropertyGrid, they are rendered as collapsible list and displays the sub elements. Let's implement a custom data type that duplicates the above functionality. In order to display a custom data type with a collapsible list, we need a TypeConverter, which converts an object type to string type and back to object. Framework also provides an ExpandableObjectConverter class (which is derived from TypeConverter class ) under System.ComponentModel namespace to implement this functionality. Create a class that defines your custom type. I am using Version number as custom type which will expand to Major,Minor,Build,Private parts.

Imports System.ComponentModel
Imports System.ComponentModel.Design.Serialization
'''

    <TypeConverter(GetType(ApplicationVersionConverter))> _
    Public Class ApplicationVersion
    '''

        Private _Major As Short
        Private _Minor As Short
        Private _Build As Short
        Private _Private As Short
        '''

        <DescriptionAttribute("Set the major part of version number")> _
        Public Property Major() As Short
            Get
                Return _Major
            End Get
            Set(ByVal Value As Short)
                _Major = Value
            End Set
        End Property
        '''

        
        <DescriptionAttribute("Set the minor part of version number")> _
        Public Property Minor() As Short
            Get
                Return _Minor
            End Get
            Set(ByVal Value As Short)
                Me._Minor = Value
            End Set
        End Property
        '''

        <DescriptionAttribute("Set the build part of version number")> _
        Public Property Build() As Short
            Get
                Return _Build
            End Get
            Set(ByVal Value As Short)
                Me._Build = Value
            End Set
        End Property
        '''

        <DescriptionAttribute("Set the private part of version number")> _
        Public Property [Private]() As Short
            Get
                Return _Private
            End Get
            Set(ByVal Value As Short)
                Me._Private = Value
            End Set
        End Property
        '''

End Class

All the above code is like the other examples, except TypeConverter attribute (<TypeConverter(GetType(ApplicationVersionConverter))>) which points to the TypeConvert class, that is used to convert our object to string and back to object. Let's implement the TypeConvert class

Friend Class ApplicationVersionConverter : Inherits ExpandableObjectConverter

Override the CanConvertTo function to indicate whether this converter can convert the object to the specified type.

 Public Overloads Overrides Function _
        CanConvertTo(ByVal context As _
        System.ComponentModel.ITypeDescriptorContext, _
        ByVal destinationType As System.Type) As Boolean

    If (destinationType Is GetType(ApplicationVersion)) Then
        Return True
    End If
    Return MyBase.CanConvertFrom(context, destinationType)
End Function

Override the CanConvertFrom function to indicate whether this converter can convert an object of one type to the type of this converter (in out case string to ApplicationVersion).

Public Overloads Overrides Function _
    CanConvertFrom(ByVal context As _
    System.ComponentModel.ITypeDescriptorContext,_
    ByVal sourceType As System.Type) As Boolean

    If (sourceType Is GetType(String)) Then
        Return True
    End If
    Return MyBase.CanConvertFrom(context, sourceType)
End Function

Override the ConvertFrom method to implement the logic to convert the string value to object. While converting make sure that the value parameter is a String.

Public Overloads Overrides Function _
    ConvertFrom(ByVal context As _
    System.ComponentModel.ITypeDescriptorContext, _
    ByVal culture As System.Globalization.CultureInfo, _
    ByVal value As Object) As Object
    
    If TypeOf value Is String Then
        Try
            Dim s As String = CType(value, String)
            Dim versionParts() As String
            Dim VersionString As String = ""
            versionParts = Split(s, ".")
            If Not IsNothing(versionParts) Then
                Dim _ApplicationVersion As _
                    ApplicationVersion = New ApplicationVersion()
                If Not IsNothing(versionParts(0)) Then 
                    _ApplicationVersion.Major = versionParts(0)
                If Not IsNothing(versionParts(1)) Then 
                    _ApplicationVersion.Minor = versionParts(1)
                If Not IsNothing(versionParts(2)) Then 
                    _ApplicationVersion.Build = versionParts(2)
                If Not IsNothing(versionParts(3)) Then 
                    _ApplicationVersion.Private = versionParts(3)
            End If
        Catch ex As Exception
            Throw New ArgumentException("Can not convert '" + _
                    value + "' to type ApplicationVersion")
        End Try
    End If
    
    Return MyBase.ConvertFrom(context, culture, value)
End Function

Override the ConvertTo method to implement the logic to convert your object back to string in a format you like. This is the value that is displayed for the parent. While converting make sure that the destinationType parameter is a String and that the value is the same type as the class.

Public Overloads Overrides Function 
         ConvertTo(ByVal context As _
         System.ComponentModel.ITypeDescriptorContext, _
         ByVal culture As System.Globalization.CultureInfo, _
         ByVal value As Object, ByVal _
         destinationType As System.Type) As Object

         If (destinationType Is GetType(System.String) AndAlso _
                  TypeOf value Is ApplicationVersion) Then
            
            Dim _ApplicationVersion As _
                ApplicationVersion = CType(value, ApplicationVersion)
            ' build the string as "Major.Minor.Build.Private"

            Return _ApplicationVersion.Major & "."_
                & _ApplicationVersion.Minor & "." & _
                _ApplicationVersion.Build & "." _
                & _ApplicationVersion.Private
        End If
        Return MyBase.ConvertTo(context, culture, value, destinationType)
End Function

and here is the final output for this article.

In the source code I have a much elaborated example, which mimic's the SQLConnectsting property.

Notes & To-Do features

In the next article I will explain about using custom editors to display properties like the docking, Graphics and tabs.