Name cannot Found InvalidOperationException

Question

4.00/5 (1 vote)

See more:

Im getting Exception that name of ellipse which is dynamically set is not found while setting StoryBoard.TargetName of DoubleAnimation....
I already have StoryBoard in my XAML...

public void CreateRandomStars()
       {

           int Width = (int)MyCanvas.Width;
           int Height = (int)MyCanvas.Height;


           Random Rnx = new Random(0);

           for (int i = 0; i < 300; i++)
           {

               double Lx = (double)Rnx.Next(Width);
               double Ty = (double)Rnx.Next(Height);
               starPoints.Add(Ty);
               Ellipse es = new Ellipse();
               es.Name = "es_" + i.ToString(); //setting names dynamically for each
               //ellipse

               es.Width = 2;
               es.Height = 2;

               es.Fill = Brushes.WhiteSmoke;
               es.SetValue(Canvas.LeftProperty, Lx);
               es.SetValue(Canvas.TopProperty, Ty);

               MyCanvas.Children.Add(es);

               DoubleAnimation dAnim = new DoubleAnimation();
               dAnim.From = Ty;
               dAnim.To = Height;
               dAnim.Duration = new Duration(new TimeSpan(0, 0, 5));
               dAnim.SetValue(Storyboard.TargetNameProperty, es.Name); //Getting Error
               dAnim.SetValue(Storyboard.TargetPropertyProperty, new PropertyPath(Canvas.TopProperty));

               MyStoryBoard.Children.Add(dAnim);

           }


       }

{"'es_0' name cannot be found in the name scope of 'System.Windows.Controls.Canvas'."}
This is the error...

XAML code

XML

<Canvas Name="MyCanvas" Background="Black" Height="310" Width="500">
        <Canvas.Triggers>
            <EventTrigger RoutedEvent="Loaded">
                <BeginStoryboard>
                    <Storyboard RepeatBehavior="Forever" Name="MyStoryBoard">
                    </Storyboard>
                </BeginStoryboard>
            </EventTrigger>
        </Canvas.Triggers>
    </Canvas>

Posted 9-Mar-11 12:47pm

greendragons

Add a Solution

2 solutions

Solution 1

I changed your XAML to below and I didn't got any exception and the stars showed up.

XML

<EventTrigger RoutedEvent="Canvas.Loaded">

Here I am calling CreateRandomStars() method from MyCanvas's Loaded event.

But when CreateRandomStars() method is called from Window's Loaded event, I am getting the error message. It is simple to understand. The Children in the Canvas is not ready when Window's Loaded event is fired. So, call the method in MyCanvas's Loaded event and change the XAML as I mentioned above.

Mark it as answer, if it is helpful.

Posted 9-Mar-11 15:30pm

Venkatesh Mookkan

Comments

greendragons 9-Mar-11 23:07pm

Sorry im new to WPF,
Im still getting error, even i changed ma XAML...maybe im making the call from wrong place...

private void MyCanvas_Loaded(object sender, RoutedEventArgs e)
{
CreateRandomStars();
}

Venkatesh Mookkan 9-Mar-11 23:12pm

Upload your sample project somewhere like http://skydrive.live.com or DropBox and give the Url. I will check and let you know.

greendragons 9-Mar-11 23:30pm

this is the link.... http://jumbofiles.com/vq0v7vorhfip
And yes stars are showing up...but i want them to move from their original Canvas.top position to
the bottom limit of canvas....tht is why im using DoubleAnimation...
Thnx!

greendragons 10-Mar-11 9:09am

I have changed to
EventTrigger RoutedEvent="Canvas.Loaded"

and
.cs file

public partial class MainWindow : Window
{
public List<double> starPoints = new List<double>();

public MainWindow()
{
InitializeComponent();

}

public void CreateRandomStars()
{

int Width = (int)MyCanvas.Width;
int Height = (int)MyCanvas.Height;

Random Rnx = new Random(0);

for (int i = 0; i < 300; i++)
{

double Lx = (double)Rnx.Next(Width);
double Ty = (double)Rnx.Next(Height);
starPoints.Add(Ty);
Ellipse es = new Ellipse();
es.Name = "es_" + i.ToString();
es.Width = 2;
es.Height = 2;

es.Fill = Brushes.WhiteSmoke;
es.SetValue(Canvas.LeftProperty, Lx);
es.SetValue(Canvas.TopProperty, Ty);

MyCanvas.Children.Add(es);

DoubleAnimation dAnim = new DoubleAnimation();
dAnim.From = Ty;
dAnim.To = Height;
dAnim.Duration = new Duration(new TimeSpan(0, 0, 5));
//dAnim.SetValue(Storyboard.TargetNameProperty, es.Name);
dAnim.SetValue(Storyboard.TargetPropertyProperty, new PropertyPath(Canvas.TopProperty));

MyStoryBoard.Children.Add(dAnim);

}

}

private void MyCanvas_Loaded(object sender, RoutedEventArgs e)
{
CreateRandomStars();
}

}

Dalek Dave 10-Mar-11 18:37pm

Worth a 5

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Abhishek Sur · Accepted Answer · 2011-03-10T09:56:00

You need to Register the name before you use it for any other control.

public void CreateRandomStars()
        {

            int Width = (int)MyCanvas.Width;
            int Height = (int)MyCanvas.Height;


            Random Rnx = new Random(0);

            for (int i = 0; i < 300; i++)
            {

                double Lx = (double)Rnx.Next(Width);
                double Ty = (double)Rnx.Next(Height);
                //starPoints.Add(Ty);
                Ellipse es = new Ellipse();
                es.Name = "es_" + i.ToString(); //setting names dynamically for each
                //ellipse

                es.Width = 2;
                es.Height = 2;

                es.Fill = Brushes.WhiteSmoke;
                es.SetValue(Canvas.LeftProperty, Lx);
                es.SetValue(Canvas.TopProperty, Ty);

                MyCanvas.Children.Add(es);

                this.RegisterName(es.Name, es);

                DoubleAnimation dAnim = new DoubleAnimation();
                dAnim.From = Ty;
                dAnim.To = Height;
                dAnim.Duration = new Duration(new TimeSpan(0, 0, 5));
                Storyboard.SetTargetName(dAnim, es.Name);
                Storyboard.SetTargetProperty(dAnim, new PropertyPath(Canvas.TopProperty));
                //StoryBoard.SetValue(Storyboard.TargetNameProperty, es.Name); //Getting Error
                //dAnim.SetValue(Storyboard.TargetPropertyProperty, new PropertyPath(Canvas.TopProperty));

                MyStoryBoard.Children.Add(dAnim);

            }


        }

The RegisterName is necessary when you want other object to refer your dynamically created element.

I hope this will work for you.