How can I manage the error:system.windows.data error: 40 : bindingexpression path error: 'isselected' property not found on 'object' ''cours' ?

Question

0.00/5 (No votes)

See more:

Hello,

I have changed the title of my question because I don't understand this error in the binding with the view.I know how to read it,but i don't understand it's cause or how should I change the syntax for it in a proper solution.This is my method for storing values:

View-Model:

public void SaveTeacher(object param)
        {

            using (DatabaseStudentsEntitiesLastStand db = new DatabaseStudentsEntitiesLastStand())
            {
              
                RegisterTeacher t = new RegisterTeacher();

                if (isChecked == true || t.CourseName != null)
                {
                    t.CourseName = courseName;

                }
                t.SNTeacher = SNTeacher;
                t.UserName = _UserName;
                t.pwd = pwd;
                t.fullName = fullName;
                t.education = education;

                db.RegisterTeachers.Attach(t);
               
                try
                {
                    db.SaveChanges();
                }
                catch (Exception ex)
                {
                   
                            MessageBox.Show(ex.Message);
                       
                }
            }
        }

This is the isChecked property:

private bool isChecked;
        public bool IsChecked
        {
            get
            {
                return IsChecked;
            }
            set
            {
                if (isChecked != value)
                {
                    isChecked = value;
                    NotifyOnPropertyChange("IsChecked");
                }
            }
        }
        private DelegateCommand checkCommand;
        public DelegateCommand CheckCommand
        {
            get
            {
                if (checkCommand == null)
                    checkCommand = new DelegateCommand(SaveTeacher, null);
                return checkCommand;
            }
            set
            {
                checkCommand = value;
                NotifyOnPropertyChange("CheckCommand");
            }
        }

This is the binding with the view:

<Button Content="Submit" Command="{Binding SaveCommand}"  HorizontalAlignment="Left" Margin="517,98.4,0,0" Grid.Row="2" VerticalAlignment="Top" Width="110" Height="40"/>
        <Button Content="Cancel"  HorizontalAlignment="Left" Margin="361,98.4,0,0" Grid.Row="2" VerticalAlignment="Top" Width="111" Height="40"/>
        <ListBox  HorizontalAlignment="Left" Name="coursesList" Height="240"   Margin="418,13.2,0,0" Grid.Row="1" VerticalAlignment="Top" Width="225" Grid.RowSpan="2"  ItemsSource="{Binding Courses}" >
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <CheckBox x:Name="CheckBoxCourses" Click="CheckBoxCourses_Click"
                              IsChecked="{Binding Path=IsChecked,UpdateSourceTrigger=PropertyChanged,Mode=TwoWay}"
                           Command="{Binding CheckCommand,Mode=TwoWay}"

                            Content="{Binding Path=courseName,Mode=TwoWay}" Margin="0"/>


                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>

This is the Checked event:

private void CheckBoxCourses_Checked(object sender, RoutedEventArgs e)
        {
            var checkbox = sender as CheckBox;
            if(checkbox!=null)
            {
                checkbox.IsChecked =true;
            }


          
        }

What I have tried:

This is the entire error:

System.Windows.Data Error: 40 : BindingExpression path error: 'IsSelected' property not found on 'object' ''Cours' (HashCode=44335814)'. BindingExpression:Path=IsSelected; DataItem='Cours' (HashCode=44335814); target element is 'CheckBox' (Name=''); target property is 'IsChecked' (type 'Nullable`1')

I have tried multiple solutions with delegatecommand,selecteditem in the listbox and IsSelected property,read-only properties,nothing is working.Since I have tried many approaches,I have moved the property IsChecked from the view-model to the model class named "Cours" along with NotifyPropertyChanged(so it basically looks like the one I have in my example,only that it is in the model,not vm).Can someone please tell me what would be the problem based on this error?Please notify me if you need certain lines of code.

Posted 10-Apr-18 22:06pm

Daniel Andrei Popescu

Updated 11-Apr-18 1:37am

v5

Add a Solution

Comments

Aydin Homay 11-Apr-18 4:18am

Hi Please copy also the method of CheckBoxCourses_Click to see how you are handling this event.

Daniel Andrei Popescu 11-Apr-18 4:26am

Hello,thank you for your response.I did that already.

1 solution

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)

Dirk Bahle · Accepted Answer · 2018-04-10T22:24:00

Solution 1

1) Look at the output window in VS while you run the app in the debugger of VS - is there a statement about a Binding Expression Error?

This may not be the exact letters and words but you should see something similar if there is a binding problem which I think you might be having here...

2) I am not seeing a SelectedItem binding - I think thats one thing you are nissing to manipulate a particular item in the list.

Hope this helps ...

Posted 10-Apr-18 22:24pm

Dirk Bahle

Comments

Daniel Andrei Popescu 11-Apr-18 4:27am

Thank you for your response,I will try this approach and I'll come back with an answer.Regarding errors in this case,I don't see any error,everything runs perfectly except for the fact that the courseName is null thanks to the checkbox.

Dirk Bahle 11-Apr-18 4:35am

This thread may be related to your problem: https://stackoverflow.com/questions/21193242/wpf-checkedlistbox-how-to-get-selected-item

Daniel Andrei Popescu 11-Apr-18 4:53am

I have tried right now to do it by using the listbox but it's still not working...Thank you for your time but i don't think i'll manage to pass the error to soon.I work on it for 2 weeks,reviewing everything ans staring back again with the binding from scratch.I have no idea why is not working...

Daniel Andrei Popescu 11-Apr-18 6:18am

I have looked at the output window and I see 2 errors for binding which are the following:
System.Windows.Data Error: 40 : BindingExpression path error: 'CheckCommand' property not found on 'object' ''Cours' (HashCode=1598569)'. BindingExpression:Path=CheckCommand; DataItem='Cours' (HashCode=1598569); target element is 'CheckBox' (Name=''); target property is 'Command' (type 'ICommand')

System.Windows.Data Error: 40 : BindingExpression path error: 'IsSelected' property not found on 'object' ''Cours' (HashCode=1598569)'. BindingExpression:Path=IsSelected; DataItem='Cours' (HashCode=1598569); target element is 'CheckBox' (Name=''); target property is 'IsChecked' (type 'Nullable`1).

Dirk Bahle 11-Apr-18 8:10am

OK it looks like you are on track towards understanding your problem with these BindingExpression errors:
System.Windows.Data Error: 40 : BindingExpression path error: 'CheckCommand' property not found on 'object' ''Cours'

means that .Net attempts to bind you command property from the checkbox as specified with:

Command="{Binding CheckCommand,Mode=TwoWay}"

. to an object of type 'Cours' but cannot do it because the command property is simply missing (or not public) at the 'Cours' class.

The second error refers to the IsSelected property binding which can also not be bound because you are missing the property in the viewmodel that is attached to the MainWindow's DataContext.

You cannot expect that the Command binding will invoke the event handler: CheckBoxCourses_Checked as these are, albeit similar, completely different ways of getting a processing request done.

You should research MVVM and WPF Binding tutorial based on simpler scenarios to understand better how this works. This Tutorial maybe helpful:
http://www.wpf-tutorial.com/data-binding/introduction/

You will see similar error messages when you implement one of their example and then (willingly) change a binding specification such that it will not find a property in the viewmodel (e.g.: specify 'XXXX' instead of 'IsSelected'). Otherwise, there are plenty of MVVM WPF examples here on CodeProject.

Dirk Bahle 11-Apr-18 8:16am

It would be helpful if you could include class names in your code listings. You should be aware that ListBox bindings usually require 2 viewmodels:
- one that contains the collection eg.: ObservableCollection<courseitem> bound to the ListBox's ItemsSource (this viewmodel can be attached to the MainWindow's DataContext)
- and one that represents an item that is displayed in the list of the ListboX (e.g.: CourseItem)

Here is a sample that demonstrates what I mean:
https://www.codeproject.com/Tips/806587/Basic-MVVM-Listbox-Binding-in-WPF

Daniel Andrei Popescu 11-Apr-18 8:33am

Thank you sir for your help.I will try it today to see if I'll get to a correct solution and I will upload the solution later on for everybody.Until then I'll mark your answer as correct so that other people can have a proper example to look at in case of a similar problem.Best wishes!