Property 'Bold' is 'ReadOnly'.

[Guest Vax]

OK, maybe this is a stupid question, I don't know. I'm running VB.NET and I'm trying to set up a few pre-arranged fonts for use in my listbox control, changing things like bold status and fontname and whatnot. So I type:

 

Dim fntFont As Font

fntFont.Bold = True

 

and I get an error that the property 'Bold' is 'ReadOnly'. What gives? do I need to attack this some other way, or am I missing something obvious?

 

:confused:

[em123]

You should post this in the VB.NET section.

 

http://www.visualbasicforum.com/f42/

[NicoVB]

You have to create a New Font I think

[divil]

Properties for Font objects are generally specified in the class constructor. If you want to modify an existing font object, you can pass it to the constructor of a new one and modify parameters there.

[Guest Vax]

Well, the class I'm sing inherits its properties from the listbox, but it does have a property set sub. The code I'm using (go it from an online magazine) is as follows:

 

Look at the public property Font. It seems to be Read/Write. What am I missing?

 

Option Explicit On

Option Strict On

Imports System.Drawing

Imports System.Drawing.Drawing2D

Imports System.Drawing.Text

Imports System.Windows.Forms

Imports System.ComponentModel

 

Namespace WKS.ODListControl

 

'Enables code gen to convert prop builder strings to ODItem

<TypeConverter(GetType(ODItemConverter))> _

Public Class ODItem

Implements IDisposable

Implements IComparable

 

Private _Image As Image

Private _Font As Font

Private _ItemHeight As Integer

Private _UserObject As Object

Private _Text As String

 

Public Sub New()

_Text = "New item"

End Sub

 

Public Sub New(ByVal text As String)

_Text = text

End Sub

 

Public Sub New(ByVal text As String, ByVal itemImage As Image, ByVal itemHeight As Integer, ByVal Font As Font)

If Not IsNothing(itemImage) Then _Image = CType(itemImage.Clone, Image)

If Not IsNothing(Font) Then _Font = CType(Font.Clone, Font)

_ItemHeight = itemHeight

_Text = text

End Sub

 

Public Sub New(ByVal userObj As Object, ByVal text As String, ByVal itemImage As Image, ByVal itemHeight As Integer, ByVal Font As Font)

If Not IsNothing(itemImage) Then _Image = CType(itemImage.Clone, Image)

If Not IsNothing(Font) Then _Font = CType(Font.Clone, Font)

_ItemHeight = itemHeight

_UserObject = userObj

_Text = text

End Sub

 

Public Property ItemHeight() As Integer

Get

Return _ItemHeight

End Get

Set(ByVal Value As Integer)

_ItemHeight = Value

End Set

End Property

 

Public Property Image() As Image

Get

Return _Image

End Get

Set(ByVal Value As Image)

_Image = Value

End Set

End Property

 

Public Function ShouldSerializeImage() As Boolean

Return (Not IsNothing(_Image))

MsgBox("Called")

End Function

 

 

Public Property DisplayText() As String

Get

Return _Text

End Get

Set(ByVal Value As String)

_Text = Value

End Set

End Property

 

Public Property UserObject() As Object

Get

Return _UserObject

End Get

Set(ByVal Value As Object)

_UserObject = Value

End Set

End Property

Public Property Font() As Font

Get

Debug.WriteLine("Get font")

Return _Font

End Get

Set(ByVal Value As Font)

_Font = Value

End Set

End Property

 

Public Overloads Sub Dispose() Implements IDisposable.Dispose

Dispose(True)

GC.SuppressFinalize(Me)

End Sub

 

Protected Overridable Overloads Sub Dispose(ByVal disposing As Boolean)

If disposing Then

'Called by Dispose()

'Free managed objects

If Not IsNothing(_Image) Then _Image.Dispose()

If Not IsNothing(_Font) Then _Font.Dispose()

End If

'Free unmanaged objects.

End Sub

 

Protected Overrides Sub Finalize()

'Protected - don't allow to be called directly

Dispose(False)

End Sub

 

Public Overrides Function toString() As String

If Len(_Text) > 0 Then

Return _Text

ElseIf Not IsNothing(UserObject) Then

Return UserObject.ToString

Else

Return String.Empty

End If

End Function

 

Public Function CompareTo(ByVal obj As Object) As Integer Implements System.IComparable.CompareTo

If IsNothing(obj) OrElse IsNothing(obj.ToString) Then Return 1

Return String.Compare(ToString, obj.ToString)

End Function

End Class

 

End Namespace

 

Well, there it is... whatcha think?

[Thinker]

Once again, as divil said, in this code...

Dim fntFont As Font

fntFont.Bold = True

You are declaring a font object variable, then (without instantiating

it) trying to set a property. Instead, you should use one of the

overloaded Font constructors to both create the font, and set the

bold property, something like...

Dim fntFont As Font = New Font(fntOldFont, FontStyle.Bold)

[Guest Vax]

sigh...

 

hmmm.... ok, but this just creates a new instance of a font. I suppose the next step is to set the font property of the object to this new font, but won't this also generate a readonly problem? I'd be trying it out right now, but I'm away from my machine. I'm betting this will probably work, I'm just having a little problem understanding why this would work but the MyObject.Font.Bold=True setting won't work, considering that MyObject is already instanced. Should that not mean the Font object of the MyObject object is also instanced, and thus the Bold Property should be read/write? It seems that would just plain make sense.

 

Y'know what's really sad about this? I'm not even getting paid to to do this, and this is how I spend my weekend. I'm sure that's saying something rather profound, not to mention unflattering.

[divil]

I guess they made that property and similar ones readonly because behind the scenes it requires a new font handle to be created, so that might as well map to a new font object being created. Seemed odd to me at first, but it's not much of an inconvenience.

 

Me.Font = New Font(Me.Font, FontStyles.Bold)

 

Or whatever it is.

[Guest Vax]

continuing further....

 

OK, that did it, thanks, but of course now I have a new problem...

how would I implement a FontColor property? Simple RGB value would be fine, but I thought the Font object would have this property inherent-- there I go thinking again, huh? I figure it would at least have a ForeColor/ BackColor property, but no...

 

Also, what would be an easy way to access the handle of the container for the control class, so I could get the container's default Font object? Is there a keyword for it, or do I have to include that in its construction arguments?

 

Thanks for the help

[Guest Vax]

another thing...

 

...how do I create a font with no reference font? Let's say I just want to make an 8-point Helvetica Italics, but don't want to reference another font, i.e.,

 

dim fntFont as Font = New Font(Me.Font, FontStyle.Bold)

 

as, in this case, the Font object might well be set to Nothing, which would generate an exception, I'm pretty sure.

 

Could someone clue me in on the sytax for that? Thanks

[divil]

Read your help. The constructor for the Font class is overloaded many times, at least one of which accepts a String with a Font Family name in it.

[Guest Vax]

FontFamily=Font Name?

 

...I must not have gotten that memo. Thanks

[Thinker]

There are about 13 overloaded constructors. This helps explain

why the Font object properties like family, style and size are read-

only. It does seem a bit obtuse, but it isn't in any way a

restriction of capabilities.