TypeConverter Support

In certain cases, RadPropertyGrid is used for displaying and editing properties of custom data type. By default, in such scenarios the control will display the custom type as a string. RadPropertyGrid provides TypeConverter support, meaning that this behavior can be modified by defining a custom TypeConverter. The main methods that are usually utilized when implementing a custom TypeConverter are listed below.

• Override the CanConvertFrom method that specifies which type the converter can convert from.

• Override the ConvertFrom method that implements the conversion.

• Override the CanConvertTo method that specifies which type the converter can convert to.

• Override the ConvertTo method that implements the conversion.

More information on implementing a TypeConverter can be found in MSDN: How to: Implement a Type Converter.

• Defining the Business Object

• Display a Predefined List of Values for a Property with TypeConverter

• Culture-aware TypeConverter

Defining the Business Object

Demonstrating the TypeConverter mechanism in the scope of RadPropertyGrid will require an object which has a property of custom data type. This section will cover the process of defining them.

The example will use a Club object which has a Captain property of type Player.

Example 1: Defining the business object

• C#
• VB.NET

 public class Club  
{ 
    private string name; 
    private Player captain;  
 
    public string Name 
    { 
        get { return this.name; } 
        set 
        { 
            if (value != this.name) 
            { 
                this.name = value; 
            } 
        } 
    } 
 
    [TypeConverter(typeof(PlayerTypeConverter))] 
    public Player Captain 
    { 
        get { return captain;} 
        set  
        {  
            captain = value; 
        } 
    } 
 
 
    public Club() 
    { 
 
    } 
 
    public Club(string name, Player captain) 
    { 
        this.name = name; 
        this.captain = captain; 
    } 
} 
 
 public class Player 
 { 
     private string name; 
     private double height; 
 
     public string Name 
     { 
         get { return this.name; } 
         set 
         { 
             if (value != this.name) 
             { 
                 this.name = value; 
             } 
         } 
     } 
 
     public double Height 
     { 
         get { return this.height; } 
         set 
         { 
             if (value != this.height) 
             { 
                 this.height = value; 
             } 
         } 
     } 
 
     public Player() 
     { 
 
     } 
 
     public Player(string name, double height) 
     { 
         this.name = name; 
         this.height = height; 
     } 
 } 

Public Class Club 
 
    Private m_name As String 
    Private m_captain As Player 
 
    Public Property Name() As String 
        Get 
            Return Me.m_name 
        End Get 
        Set(value As String) 
            If value <> Me.m_name Then 
                Me.m_name = value 
            End If 
        End Set 
    End Property 
 
    <TypeConverter(GetType(PlayerTypeConverter))> _ 
    Public Property Captain() As Player 
        Get 
            Return m_captain 
        End Get 
        Set(value As Player) 
            m_captain = value 
        End Set 
    End Property 
 
    Public Sub New() 
    End Sub 
 
    Public Sub New(name As String, captain As Player) 
        Me.m_name = name 
        Me.m_captain = captain 
    End Sub 
End Class 
 
 
Public Class Player 
 
    Private m_name As String 
    Private m_height As Double 
 
    Public Property Name() As String 
        Get 
            Return Me.m_name 
        End Get 
        Set(value As String) 
            If value <> Me.m_name Then 
                Me.m_name = value 
            End If 
        End Set 
    End Property 
 
    Public Property Height() As Double 
        Get 
            Return Me.m_height 
        End Get 
        Set(value As Double) 
            If value <> Me.m_height Then 
                Me.m_height = value 
            End If 
        End Set 
    End Property 
 
    Public Sub New() 
    End Sub 
 
    Public Sub New(name As String, height As Double) 
        Me.m_name = name 
        Me.m_height = height 
    End Sub 
End Class 

Display a Predefined List of Values for a Property with TypeConverter

As of R1 2017, the TypeConverter mechanism of RadPropertyGrid provides support for a standard set of values that can be picked from a predefined list. This can be done through overriding the GetStandardValuesSupported method.

Example 2: Defining a TypeConverter providing a default set of values

• C#
• VB.NET

 public class PlayerTypeConverter : TypeConverter 
 { 
     public override bool GetStandardValuesSupported(ITypeDescriptorContext context) 
     { 
         return true; 
     } 
 
     public override bool GetStandardValuesExclusive(ITypeDescriptorContext context) 
     { 
         return true; 
     } 
 
     public override StandardValuesCollection GetStandardValues(ITypeDescriptorContext context) 
     { 
 
         return new StandardValuesCollection(new string[] { "Mark Wright", "Ian Rush", "John Barnes", 
                "Paul Ince", "Jamie Redknapp", "Sami Hyypia", "Steven Gerrard ", "Jordan Henderson" }); 
     } 
 } 

Public Class PlayerTypeConverter 
    Inherits TypeConverter 
    Public Overrides Function GetStandardValuesSupported(context As ITypeDescriptorContext) As Boolean 
        Return True 
    End Function 
 
    Public Overrides Function GetStandardValuesExclusive(context As ITypeDescriptorContext) As Boolean 
        Return True 
    End Function 
 
    Public Overrides Function GetStandardValues(context As ITypeDescriptorContext) As StandardValuesCollection 
 
        Return New StandardValuesCollection(New String() {"Mark Wright", "Ian Rush", "John Barnes", "Paul Ince", "Jamie Redknapp", "Sami Hyypia", _ 
            "Steven Gerrard ", "Jordan Henderson"}) 
    End Function 
End Class 

If EditorAttribute is set to a specific property with a set TypeConverter the EditorAttribute is with lower priority - a default set of values will be visualized if the GetStandardValuesSupported is overridden instead of an editor.

Figure 1: TypeConverter providing a default set of values

Culture-aware TypeConverter

In this section, the definition of a culture aware TypeConverter will be demonstrated. The support for it is added as of R1 2017. For this purpose, the Height property of the Player object will be used.

Example 3: Defining a culture aware TypeConverter

• C#
• VB.NET

 public class PlayerTypeConverter1 : TypeConverter 
 { 
     private const double inchesToCentimetres = 2.54; 
     private const double centimetresToInches = 0.3937008; 
 
     public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType) 
     { 
         if (sourceType == typeof(string)) 
         { 
             return true; 
         } 
 
         return base.CanConvertFrom(context, sourceType); 
     } 
 
     public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType) 
     { 
         if (destinationType == typeof(string)) 
         { 
             return true; 
         } 
 
         return base.CanConvertTo(context, destinationType); 
     } 
 
     public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value) 
     { 
         if (!(value is string)) 
         { 
             return base.ConvertFrom(context, culture, value); 
         } 
 
         string val = (string)value; 
 
         string measure = val.Substring(val.Length - 2, 2).ToLower(); 
         string dispValue = val.Substring(0, val.Length - 2); 
         double disp = double.Parse(dispValue); 
 
         if (measure.ToLower() == "ft") 
         { 
             return disp; 
         } 
         else 
         { 
             return disp * centimetresToInches; 
         } 
     } 
 
     public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType) 
     { 
         if (!(destinationType == typeof(string))) 
         { 
             return base.ConvertTo(context, culture, value, destinationType); 
         } 
 
         RegionInfo regionInfo = new RegionInfo(culture.LCID); 
         bool metric = regionInfo.IsMetric; 
 
         if (metric) 
         { 
             return string.Format("{0:F0}cm", (value as Player).Height); 
         } 
         else 
         { 
             double inches = (value as Player).Height * inchesToCentimetres; 
 
             return string.Format("{0:F0}ft", inches); 
         } 
     } 
 } 

Public Class PlayerTypeConverter1 
    Inherits TypeConverter 
    Private Const inchesToCentimetres As Double = 2.54 
    Private Const centimetresToInches As Double = 0.3937008 
 
    Public Overrides Function CanConvertFrom(context As ITypeDescriptorContext, sourceType As Type) As Boolean 
        If sourceType = GetType(String) Then 
            Return True 
        End If 
 
        Return MyBase.CanConvertFrom(context, sourceType) 
    End Function 
 
    Public Overrides Function CanConvertTo(context As ITypeDescriptorContext, destinationType As Type) As Boolean 
        If destinationType = GetType(String) Then 
            Return True 
        End If 
 
        Return MyBase.CanConvertTo(context, destinationType) 
    End Function 
 
    Public Overrides Function ConvertFrom(context As ITypeDescriptorContext, culture As CultureInfo, value As Object) As Object 
        If Not (TypeOf value Is String) Then 
            Return MyBase.ConvertFrom(context, culture, value) 
        End If 
 
        Dim val As String = DirectCast(value, String) 
 
        Dim measure As String = val.Substring(val.Length - 2, 2).ToLower() 
        Dim dispValue As String = val.Substring(0, val.Length - 2) 
        Dim disp As Double = Double.Parse(dispValue) 
 
        If measure.ToLower() = "ft" Then 
            Return disp 
        Else 
            Return disp * centimetresToInches 
        End If 
    End Function 
 
    Public Overrides Function ConvertTo(context As ITypeDescriptorContext, culture As CultureInfo, value As Object, destinationType As Type) As Object 
        If Not (destinationType = GetType(String)) Then 
            Return MyBase.ConvertTo(context, culture, value, destinationType) 
        End If 
 
        Dim regionInfo As New RegionInfo(culture.LCID) 
        Dim metric As Boolean = regionInfo.IsMetric 
 
        If metric Then 
            Return String.Format("{0:N2}cm", TryCast(value, Player).Height) 
        Else 
            Dim inches As Double = TryCast(value, Player).Height * inchesToCentimetres 
 
            Return String.Format("{0:F1}ft", inches) 
        End If 
    End Function 
End Class 

Figure 2: Culture-aware TypeConverter