Generic way to pass a telerik ThemePalette to a sub/function?

[Rob A.]

I'm trying to pass  a Telerik CrystalPalette to a Sub but I get an error "...is class type and can not be used as an expression".  Hints?

Public Function DoSomething() As Boolean

   ApplyThemeFontSizes(CrystalTheme)

End Function

Private Sub ApplyThemeFontSizes(Of T)()

        Try

            T.Palette.FontSizeXS = 8 + Me.FontOffset
            T.Palette.FontSizeS = 10 + Me.FontOffset
            T.Palette.FontSize = 12 + Me.FontOffset
            T.Palette.FontSizeL = 14 + Me.FontOffset
            T.Palette.FontSizeXL = 16 + Me.FontOffset

        Catch ex As Exception

            ' TODO: Log error to file (possible the Theme doesn't have a "Palette")

        End Try

    End Sub

[Martin Ivanov]

Hello Robin,

The Palette property of each palette is defined in each separate palette class. It is not inherited, so you won't be able to use a generic method without parameters. Each palette is unique and has a set of properties which may vary in naming. This is most valid for the brushes of the palette. The FontSize properties are also not inherited from the child ThemePalette class. In other words, you will need to check for the specific palette implementation and set its FontSize.

On way to achieve your requirement without hard-coding the palettes or if-else statements that check them is to use a reflection. For example:

Public Sub DoSomething()
	ApplyThemeFontSizes(CrystalPalette.Palette)
End Sub

Public Property FontOffset As Double = 10

Private Sub ApplyThemeFontSizes(ByVal palette As ThemePalette)
	TrySetPaletteProperty(palette, "FontSizeXS", 8 + Me.FontOffset)
	TrySetPaletteProperty(palette, "FontSizeS", 10 + Me.FontOffset)
	TrySetPaletteProperty(palette, "FontSize", 12 + Me.FontOffset)
	TrySetPaletteProperty(palette, "FontSizeL", 14 + Me.FontOffset)
	TrySetPaletteProperty(palette, "FontSizeXL", 16 + Me.FontOffset)
End Sub

Private Function TrySetPaletteProperty(ByVal palette As ThemePalette, ByVal propertyName As String, ByVal newValue As Object) As Boolean
	Dim propertyInfo = palette.[GetType]().GetProperty(propertyName, System.Reflection.BindingFlags.[Static] Or System.Reflection.BindingFlags.[Public])
	If propertyInfo IsNot Nothing Then
		propertyInfo.SetValue(palette, newValue)
		Return True
	End If
	Return False
End Function

I hope this helps. 

Regards,
Martin Ivanov
Progress Telerik

[Rob A.]

Martin,

Thanks for the response, unfortunately your code sample doesn't work ... propertyInfo always comes back as Nothing so the SetValue never happens.

NOTE: verified the palette does exist for the selected theme

Cheers, Rob.

[Martin Ivanov]

Hello Robin,

It looks like the GetProperty() method doesn't need the BindingFlags in VB.NET. To get the property info, remove the flags from the GetProperty() method call. 

Dim propertyInfo = palette.GetType().GetProperty(propertyName)

Regards,
Martin Ivanov
Progress Telerik