System windows data error 40

Greetings;

        public CallStackDialog(Window owner,
               FormattedStackTrace stackTrace)
        {
            InitializeComponent();
            this.Owner = owner;

            StackTrace = stackTrace;
            DataContext = StackTrace;

            return;
        }

        private FormattedStackTrace formattedStackTrace;

        public FormattedStackTrace StackTrace
        {
            get
            {
                return formattedStackTrace;
            }

            set
            {
                formattedStackTrace = value;
                NotifyPropertyChanged("StackTrace");
            }
        }

3.) The FormattedStackTrace class contains an instance of List<OrderedCall> as an auto property named OrderedStackTrace.  I am trying to bind this collection as the ItemsSource for the DataGrid in the window. The relative members of the FormattedStackTrace,
which is the backing reference type for the Window’s DataContext, is as follows:

    public class FormattedStackTrace
    {
#region FormattedStackTrace Class Data Members & Auto-Properties

        private StackFrame[] sourceStackFrame;
        public MethodBase CallingMethod { get; private set; }
        public List<OrderedCall> OrderedStackTrace { get; private set; }

#endregion
    }

OrderedStackTrace is a List<OrderedCall>, where each List member is an instance of the following structure:

    public struct OrderedCall
    {
        public int Call;
        public string Method;
    }; 

At the point where the DataContext is set inside the parent Window’s class constructor, the OrderedStackTrace property is correct, in that it contains the expected number of OrderedCall instance values, and they can be viewed without issue inside any of the
Debugging tabs inside Visual Studio 2010, or inside the IDE’s Immediate Window:

    ? StackTrace.OrderedStackTrace == null
    false
    ? StackTrace.OrderedStackTrace.Count
    40
    ? StackTrace.OrderedStackTrace[39]
    {WPFEventHandling.OrderedCall}
        Call: 40
        Method: «WPFEventHandling.MainWindow.OnMousePointerEnteredButton(Object sender, MouseEventArgs e)»

4.) The DataGrid inside the Window I’m trying to bind to, StackTraceDataGrid, which is read only, is implemented in XAML as follows:

<DataGrid Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2" 
          Name="StackTraceDataGrid" IsReadOnly="True"
          AutoGenerateColumns="False" Margin="10" 
          ItemsSource="StackTrace.OrderedStackTrace">
    <DataGrid.Columns>
        <DataGridTextColumn Header="Offest" 
         Binding="{Binding Call}" Width="60">
        </DataGridTextColumn>
        <DataGridTextColumn Header="Method" 
         Binding="{Binding Method}" Width="*">
        </DataGridTextColumn>
    </DataGrid.Columns>
</DataGrid>

When I build the solution containing this Window and  the child StackTraceDataGrid control, there are no errors nor compiler warnings. When I bring up the parent window that contains StakTraceDataGrid, the DataGrid and the two Text Columns, Offset and
Method, are rendered and formatted as expected, but each row in the DataGrid is empty.  When the Window is brought up, the following set of runtime messages appear for each pair of OrderedCall member values in each column for each row:

System.Windows.Data Error: 40 : BindingExpression path error: ‘Call’ property not found on ‘object’ »Char’ (HashCode=7471218)’. BindingExpression:Path=Call; DataItem=’Char’ (HashCode=7471218); target element is ‘TextBlock’ (Name=»); target property is ‘Text’
(type ‘String’)
System.Windows.Data Error: 40 : BindingExpression path error: ‘Method’ property not found on ‘object’ »Char’ (HashCode=7471218)’. BindingExpression:Path=Method; DataItem=’Char’ (HashCode=7471218); target element is ‘TextBlock’ (Name=»); target property is
‘Text’ (type ‘String’)

As far as I can tell, I think that my problem may lie in how I’ve defined the ItemsSource property for the DataGrid, and the Binding Path for each column for each instance of OrderedCall as I would like to have displayed in each row of the Grid.

I would really appreciate any corrections on how to resolve the BindingExpression path errors I’m seeing at runtime, as well as any background informatio on what each DataGrid Column is expecting for a Binding Path for each item in each row of the DataGrid.

Thank you in advance for your time and help, and I look forward to hearing from you soon.

System windows data error 40 bindingexpression path error

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Answered by:

Question

I’m having difficulty using WPF’s support for Data Binding a generic List<> instance to a Read-Only DataGrid inside a Window. To setup the Data Binding, I have the following in place in the code:

1.) I set the Window’s DataContext to a reference type of FormattedStackTrace exposed as a public property named StackTrace. The DataContext is set in the Window’s class constructor in C# as follows:

The instance of StackTrace is non-null, and I can access and view all of its property members through the StackTrace property as expected. Likewise, the Window’s DataContext is a non-null value.

2.) The StackTrace property is implemented in the same window class as follows:

3.) The FormattedStackTrace class contains an instance of List as an auto property named OrderedStackTrace. I am trying to bind this collection as the ItemsSource for the DataGrid in the window. The relative members of the FormattedStackTrace, which is the backing reference type for the Window’s DataContext, is as follows:
OrderedStackTrace is a List , where each List member is an instance of the following structure:
At the point where the DataContext is set inside the parent Window’s class constructor, the OrderedStackTrace property is correct, in that it contains the expected number of OrderedCall instance values, and they can be viewed without issue inside any of the Debugging tabs inside Visual Studio 2010, or inside the IDE’s Immediate Window:

? StackTrace.OrderedStackTrace == null
false
? StackTrace.OrderedStackTrace.Count
40
? StackTrace.OrderedStackTrace[39]

Call: 40
Method: «WPFEventHandling.MainWindow.OnMousePointerEnteredButton(Object sender, MouseEventArgs e)»

4.) The DataGrid inside the Window I’m trying to bind to, StackTraceDataGrid, which is read only, is implemented in XAML as follows:

When I build the solution containing this Window and the child StackTraceDataGrid control, there are no errors nor compiler warnings. When I bring up the parent window that contains StakTraceDataGrid, the DataGrid and the two Text Columns, Offset and Method, are rendered and formatted as expected, but each row in the DataGrid is empty. When the Window is brought up, the following set of runtime messages appear for each pair of OrderedCall member values in each column for each row:

System.Windows.Data Error: 40 : BindingExpression path error: ‘Call’ property not found on ‘object’ »Char’ (HashCode=7471218)’. BindingExpression:Path=Call; DataItem=’Char’ (HashCode=7471218); target element is ‘TextBlock’ (Name=»); target property is ‘Text’ (type ‘String’)
System.Windows.Data Error: 40 : BindingExpression path error: ‘Method’ property not found on ‘object’ »Char’ (HashCode=7471218)’. BindingExpression:Path=Method; DataItem=’Char’ (HashCode=7471218); target element is ‘TextBlock’ (Name=»); target property is ‘Text’ (type ‘String’)

As far as I can tell, I think that my problem may lie in how I’ve defined the ItemsSource property for the DataGrid, and the Binding Path for each column for each instance of OrderedCall as I would like to have displayed in each row of the Grid.

I would really appreciate any corrections on how to resolve the BindingExpression path errors I’m seeing at runtime, as well as any background informatio on what each DataGrid Column is expecting for a Binding Path for each item in each row of the DataGrid.

Thank you in advance for your time and help, and I look forward to hearing from you soon.

Источник

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.

I guess it is the error message that seems having nothing to do with Win Form makes people hesitate to response to your question. The error message looks like somehow related to WPF UI. Also, when you say «… show this in debug», what does «debug» mean? where exactly do you see the error message? A pop-up window in AutoCAD, where you can click either «Detail» to see more error message, or «Continue», which would either let AutoCAD continue. if the error is not that fatal, or let AutoCAD die?

Anyway, if your Form1 is a true win form, regardless the strange error, your code in the CommandMethod is very wrong, in 2 ways:

1. You DO NOT show dialog form (modal view) with Form.ShowDialog() in AutoCAD .NET API add-in. You must use AutoCAD .NET API method

Autodesk.AutoCAD.ApplicationServices.Application.ShowModalDialog[Window]()

2. You DO NOT sandwich all the code (showing the dialog box, and then user may do something to AutoCAD by interacting with the form) with a Transaction and only not commit it (which means whatever user does to AutoCAD would be aborted when you close the dialog form. That is why the line drawn by the button clicking action is not there: it is lost after you close the form. because the outer-most transaction is not commited (thus, aborted automatically).

While letting UI’s event handler (button clicking, in your case) directly interact with AutoCAD isn’t a very good code practice, I think you can live with that for now (as beginner?), thus, the simple fix to your code is to modify the CommandMethed as following:

       [CommandMethod("ACADPipe")]
        public static void pipe()
        {
            using (Form1 form1 = new Form1())
            {
                Application.ShowModalDialog(form1);
            }
        }

And, in your drawTestLine_Click() method, you might want to add

ed.UpdateScreen()

at the end of the Transaction, if you want the newly created line to be seen without dismissing the dialog box.