Re: Cannot set a property on object 'Identity' because it is in a read-only state. - WPF Discussion Boards

Re: Cannot set a property on object 'Identity' because it is in a read-only state.

9-Jul-09 3:08

I am getting a eroor from my code, i cant trace the issue/bug . here is my code bit...

private void DoArrange()<br />
        {<br />
            Point center = new Point((this.Width - ItemSize) / 2, (this.Height - ItemSize) / 2);<br />
            double radiusX = center.X;<br />
            double radiusY = center.Y;<br />
            double scale = ScalePerspective;<br />
<br />
            for (int i = 0; i &lt; Children.Count; i++)<br />
            {<br />
                UIElement item = Children[i];<br />
                double radians = (double)item.GetValue(CarouselPanel.AngleProperty);<br />
<br />
                Point p = new Point(<br />
                                    (Math.Cos(radians) * radiusX) + center.X,<br />
                                    (Math.Sin(radians) * radiusY) + center.Y<br />
                                   );<br />
<br />
                if (item.RenderTransform == null)<br />
                {<br />
                    item.RenderTransform = new MatrixTransform();<br />
                    item.RenderTransformOrigin = new Point(0.5, 0.5);<br />
                }<br />
                MatrixTransform mt = item.RenderTransform as MatrixTransform;<br />
                double scaleMinusRounding = p.Y / (center.Y + radiusY);<br />
                double scaleX = Math.Min(scaleMinusRounding + scale, 1.0);<br />
                double scaleY = Math.Min(scaleMinusRounding + scale, 1.0);<br />
                Matrix mx = new Matrix(scaleX, 0.0, 0.0, scaleY, 0.0, 0.0);<br />
            <br />
               mt.Matrix = mx;<br />
                item.RenderTransform = mt;<br />
                <br />
                int zIndex = (int)((p.Y / base.Height) * 50);<br />
                item.SetValue(Canvas.ZIndexProperty, zIndex);<br />
                Rect r = new Rect(p.X, p.Y, ItemSize, ItemSize);<br />
                item.Arrange(r);<br />
            }<br />
        }

What could be the issue i am using a WPF(win) application.

modified on Thursday, July 9, 2009 9:48 AM

Pete O'Hanlon9-Jul-09 3:33

9-Jul-09 3:33

I can't see the Identity property in your code. Are you sure this is where the problem is?

"WPF has many lovers. It's a veritable porn star!" - Josh Smith

As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.

Re: Cannot set a property on object 'Identity' because it is in a read-only state.

ASysSolvers9-Jul-09 3:50

Re: Cannot set a property on object 'Identity' because it is in a read-only state.

9-Jul-09 3:50

I edidted the post again,..the error raised from the underlined statement..

Pete O'Hanlon9-Jul-09 4:13

9-Jul-09 4:13

Basically, you have a frozen object here (you can tell this by checking mt.Matrix.IsFrozen). Once an object is frozen, you can't modify it - instead, you have to clone it and work with that.

"WPF has many lovers. It's a veritable porn star!" - Josh Smith

As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.

Re: Cannot set a property on object 'Identity' because it is in a read-only state.

ASysSolvers9-Jul-09 4:27

Re: Cannot set a property on object 'Identity' because it is in a read-only state.

9-Jul-09 4:27

Pete O'Hanlon wrote:
(you can tell this by checking mt.Matrix.IsFrozen).

i cannot find any handle like that, but i found something mt.Matrix.IsIdentity which is returns a bool value. What it does?..

Your corperation is really appreciated!

Pete O'Hanlon9-Jul-09 4:38

9-Jul-09 4:38

ASysSolvers wrote:
i cannot find any handle like that, but i found something mt.Matrix.IsIdentity which is returns a bool value. What it does?..

This property identifies whether or not a matrix is the identity matrix. Basically, an identity matrix is a square matrix which has 1s on the main diagonal and 0s elsewhere.

"WPF has many lovers. It's a veritable porn star!" - Josh Smith

As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.

Re: Cannot set a property on object 'Identity' because it is in a read-only state.

ASysSolvers9-Jul-09 5:03

PropertyChanged Nofification

9-Jul-09 5:03

Do you have any idea to modify my code in the correct way?.. im struggled now.. i dont knw,.. i want to use this in WPF(Windows) application,..but fine in web it works,..
In windows it gives runtine error like in Thread subject..

schiebel-t9-Jul-09 1:22

schiebel-t

9-Jul-09 1:22

Hello,

Currently im hanging on one Problem. I wrote a class inherting from grid. Each grid has the property
children. How can i get an notification when a new children added to the grid. I need somethink like a
event which occours when the children-cout changed. I hope you understand what i mean.

Thanks in advanced

Re: PropertyChanged Nofification

Pete O'Hanlon9-Jul-09 1:38

9-Jul-09 1:38

You're looking at the ObservableCollection - that notifies you when an item has been added or removed from a collection.

"WPF has many lovers. It's a veritable porn star!" - Josh Smith

As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.

Re: PropertyChanged Nofification

up_late21-Jul-09 13:33

up_late

21-Jul-09 13:33

The Children property of a Grid is a UIElementCollection, which is not Observable, and is sealed.

So I have the same question - is there any way to see if the Children collection in a Panel has changed?

WPF Toolkit: DataGrid disbled the cell

laprathab9-Jul-09 0:15

laprathab

9-Jul-09 0:15

I am using wpf toolkit:Datagrid in my application with one Check box column and another textbox column. By default textbox column is Readonly.If Check box is checked then editing the textbox for particular row.
How can achieve the above scenario?...Thanks in advance

default control template xaml

Bob Bedell8-Jul-09 13:28

8-Jul-09 13:28

Does anyone know where to find the complete default control template xaml listings for the WPF controls?

Thanks.

Bob

Kamal Gurnani9-Jul-09 1:06

Kamal Gurnani

9-Jul-09 1:06

The WPF documentation doesn’t list the XAML for standard control templates. But, you can write program to get the control template and then modify it and Re-Apply it.

Here is the program to get the control Template Markup of a given control.

In a Main window take a listbox control to enlist all the controls, and when any item is selected the corrosponding Control Template's Markup is displayed in a Textblock control.

Here is the WPF program to demonstrate the same

This is the XAML part
<Window x:Class="DefaultControlTemplate.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="462" Width="572" Loaded="Window_Loaded" >
<Grid>
<ListBox Margin="12,12,0,12" Name="listBox1" HorizontalAlignment="Left" Width="168" SelectionChanged="listBox1_SelectionChanged" />
<TextBlock HorizontalAlignment="Right" Margin="0,14,12,10" Name="textBlock1" Width="159" />
</Grid>
</Window>

This is how .cs file would look like

private void Window_Loaded(object sender, RoutedEventArgs e)
{
Type controlType = typeof(Control);
List<Type> ctrlTypes = new List<Type>();

//searches all the types in a dll where generic control class is defined

Assembly assembly = Assembly.GetAssembly(typeof(Control));

foreach (Type type in assembly.GetTypes())
{
// Only add a type of the list if it's a Control, a concrete class,
// and public.
if (type.IsSubclassOf(controlType) && !type.IsAbstract && type.IsPublic)
{
ctrlTypes.Add(type);

}
}

listBox1.ItemsSource = ctrlTypes;

}

------------------------------------------------------------

private void listBox1_SelectionChanged(object sender, SelectionChangedEventArgs e)
{

try
{

// Get the selected type.
Type type = (Type)listBox1.SelectedItem;

// Instantiate the type.
ConstructorInfo info = type.GetConstructor(System.Type.EmptyTypes);
Control control = (Control)info.Invoke(null);

// Get the template.
ControlTemplate template = control.Template;

// Get the XAML for the template.
XmlWriterSettings settings = new XmlWriterSettings();
settings.Indent = true;
StringBuilder sb = new StringBuilder();
XmlWriter writer = XmlWriter.Create(sb, settings);
XamlWriter.Save(template, writer);
textBlock1.Text = sb.ToString();

}

catch (Exception err)
{
textBlock1.Text = "<< Error generating template: " + err.Message + ">>";
}
}
---------------------------------------------------------

Let me explain the code:

At the Window_loaded event, I have enlisted all the controls in a list box.

When any of the items from list box is selected, I have created the control as per selection, got it's control template and serialized into XML and displayed the same in textblock as text.

If you want, you can start with a simpler program, say a window has a button and a textblock. When clicked on button,
the corrosponding XAML for button's control template will be displayed in textblock. In this case, Button is instantiated, hence need to created Button Object, as shown below.

private void button1_Click(object sender, RoutedEventArgs e)
{
ControlTemplate template = ((Control)sender).Template;
XmlWriterSettings settings = new XmlWriterSettings();
settings.Indent = true;
StringBuilder sb = new StringBuilder();
XmlWriter writer = XmlWriter.Create(sb, settings);
XamlWriter.Save(template, writer);
label1.Content = sb.ToString();

}

Bob Bedell9-Jul-09 12:02

9-Jul-09 12:02

I ran your first version which looks promising, only the line:

ControlTemplate template = control.Template;

Always assigns a null value to the template variable.

The error message is typically:

<< Error generating template: Parameter name: obj>>

Are you seeing the same thing?

Thanks for your reply,

Bob

Bob Bedell9-Jul-09 12:04

9-Jul-09 12:04

The error is obviously thrown by the line:

XamlWriter.Save(template, writer);

since template is null.

Bob Bedell9-Jul-09 16:12

9-Jul-09 16:12

It appears that when you construct a WPF control in code, its Template property isn't initialized. For example:

ListBox listBox = new ListBox();

If you instantiate a ListBox like this, then walk the object hierarchy down to the Template property of the Control base class, you'll see that it hasn't been initilaized.

Bob Bedell11-Jul-09 4:08

11-Jul-09 4:08

Turns out, after a little more exploration, that the Template property will be null unless the control has been rendered on the screen.

textbox - select all

teejayem8-Jul-09 6:07

teejayem

8-Jul-09 6:07

I know it sounds stupid but i'm looking for a way to style a textbox so that when it has focus it selects all the text. I know I could just call 'textBox.SelectAll()' (but i like to avoid x:Name). I could subclass the textbox and override OnFocus and call "SelectAll()" (but i don't like the idea). I'd really like to be able to do this in xaml by creating a style. I did a google check but came up empty Frown | :(

EDIT:
i just came across this solution[^]. I'm really hoping for a pure xaml solution but this will work.

Don't be overcome by evil, but overcome evil with good

Re: textbox - select all

User 2710099-Jul-09 18:23

User 271009

9-Jul-09 18:23

This is what I use in all my applications.

http://www.madprops.org/blog/wpf-textbox-selectall-on-focus/[^]

Cheers, Karl

» CodeProject 2008 MVP, CodeProject 2009 MVP

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Just a grain of sand on the worlds beaches.

modified 27-Feb-21 21:01pm.

Message Removed

8-Jul-09 3:45

N_tro_P

8-Jul-09 3:45

Message Removed

Re: WPF Charting

Pete O'Hanlon8-Jul-09 4:41

8-Jul-09 4:41

Have you had a look at the WPF Chart Controls[^] in the WPF Toolkit?

"WPF has many lovers. It's a veritable porn star!" - Josh Smith

As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.