DataContext Błąd

Question

Dobry wieczór mam mały problem z programem w Wpf który wyświetla mi taki błąd "Odwołanie do obiektu nie zostało ustawione na wystąpienie obiektu.". Całkowicie nie wiem co zrobiłem źle dlatego proszę o pomoc i ewentualne wytłumaczenie rozwiązania. Oto kod 
(strona główna po zaznaczeniu check box siatka powinno nam się pojawić dodatkowe okno które pyta o jednostkę siatki a po podaniu jej rysuje siatkę na canvie zgodnie z podaną jednostką)

<Window x:Class="WpfApp1.Windows.DrawPage"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1.Windows"
        mc:Ignorable="d"

      Title="DrawPage" Height="900" Width="1600"
      Background="Wheat">
    <ScrollViewer HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden" Height="900">
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="auto"></ColumnDefinition>
                <ColumnDefinition Width="auto"></ColumnDefinition>
                <ColumnDefinition Width="auto"></ColumnDefinition>
                <ColumnDefinition Width="auto"></ColumnDefinition>
                <ColumnDefinition Width="*"></ColumnDefinition>
                <ColumnDefinition Width="*"></ColumnDefinition>
                <ColumnDefinition Width="*"></ColumnDefinition>
            </Grid.ColumnDefinitions>

            <Grid.RowDefinitions>
                <RowDefinition Height="auto"></RowDefinition>
                <RowDefinition Height="auto"></RowDefinition>
                <RowDefinition Height="auto"></RowDefinition>
                <RowDefinition Height="auto"></RowDefinition>
                <RowDefinition Height="auto"></RowDefinition>
                <RowDefinition Height="auto"></RowDefinition>
                <RowDefinition Height="auto"></RowDefinition>
                <RowDefinition Height="auto"></RowDefinition>
                <RowDefinition Height="auto"></RowDefinition>
                <RowDefinition Height="auto"></RowDefinition>
                <RowDefinition Height="auto"></RowDefinition>
            </Grid.RowDefinitions>

            <Label Grid.ColumnSpan="2" Content="Rysunek" FontSize="40" VerticalAlignment="Center" HorizontalContentAlignment="Center"></Label>
            
            <Label Grid.Row="1" Grid.Column="0" FontSize="20" Content="Podaj X1:"></Label>
            <TextBox Grid.Row="1" Width="100" HorizontalAlignment="Left" Grid.Column="1" Height="50" x:Name="pointX1" HorizontalContentAlignment="Center" VerticalContentAlignment="Center" PreviewTextInput="Validation"></TextBox>

            <Label Grid.Row="1" Grid.Column="2" FontSize="20" Content="Podaj X2:"></Label>
            <TextBox Grid.Row="1" Width="100" HorizontalAlignment="Left" Grid.Column="3" Height="50" x:Name="pointX2" HorizontalContentAlignment="Center" VerticalContentAlignment="Center" PreviewTextInput="Validation"></TextBox>

            <Label Grid.Row="2" Grid.Column="0" FontSize="20" Content="Podaj Y1:"></Label>
            <TextBox Grid.Row="2" Width="100" HorizontalAlignment="Left" Grid.Column="1" Height="50" x:Name="pointY1" HorizontalContentAlignment="Center" VerticalContentAlignment="Center" PreviewTextInput="Validation"></TextBox>

            <Label Grid.Row="2" Grid.Column="2" FontSize="20" Content="Podaj Y2:"></Label>
            <TextBox Grid.Row="2" Width="100" HorizontalAlignment="Left" Grid.Column="3" Height="50" x:Name="pointY2" HorizontalContentAlignment="Center" VerticalContentAlignment="Center" PreviewTextInput="Validation"></TextBox>

            <Label Grid.Row="3" Grid.Column="0"  FontSize="20" Content="Okrąg" VerticalContentAlignment="Center"></Label>
            <CheckBox Grid.Row="3" Grid.Column="1" VerticalAlignment="Center"></CheckBox>

            <Label Grid.Row="4" Grid.Column="0"  FontSize="20" Content="Trójkąd" VerticalContentAlignment="Center"></Label>
            <CheckBox Grid.Row="4" Grid.Column="1" VerticalAlignment="Center"></CheckBox>

            <Label Content="Siatka" x:Name="siatka" Grid.Row="5" Grid.Column="0"  FontSize="20" VerticalContentAlignment="Center"></Label>
            <CheckBox x:Name="siatkaCheck" Grid.Row="5" Grid.Column="1" Checked="CheckBoxSiatka_Checked" VerticalAlignment="Center"></CheckBox>

            <Label Content="Pokaż osie:" Grid.Row="6" Grid.Column="0"  FontSize="20" VerticalContentAlignment="Center"/>
            <CheckBox x:Name="Osie" Checked="Osie_Checked" Unchecked="Osie_Unchecked" Grid.Row="6" Grid.Column="1" VerticalAlignment="Center"></CheckBox>

            <Button Content="Rysuj" Grid.Row="7" Grid.Column="0" Grid.ColumnSpan="4" Height="50" Click="DrawBtn" Margin="10"></Button>
            <Button Content="Czysc" Grid.Row="8" Grid.Column="0" Grid.ColumnSpan="4" Height="50" Click="ClearBtn" Margin="10"></Button>

            <Canvas x:Name="canvas" Background="White" 
                    Margin="20" Grid.Row="1" Grid.Column="4" 
                    Width="800" Height="600" 
                    Grid.RowSpan="11" Grid.ColumnSpan="3"/>
        </Grid>
    </ScrollViewer>
</Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.NetworkInformation;
using System.Runtime.CompilerServices;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
using System.Xaml.Schema;

namespace WpfApp1.Windows
{
    /// <summary>
    /// Logika interakcji dla klasy DrawPage.xaml
    /// </summary>
    /// 

    class HightValueException : Exception
    {
        public HightValueException() : base("Wartości przekraczają wielkość płótna")
        {

        }
    }

    class StringValueException : Exception
    {
        public StringValueException() : base("Wartośći X i Y nie mogą być puste")
        {

        }
    }

    public partial class DrawPage : Window
    {
        public DrawPage()
        {
            InitializeComponent();
        }

        private void DrawBtn(object sender, RoutedEventArgs e)
        {
            try
            {
                if (String.IsNullOrEmpty(pointX1.Text) || String.IsNullOrEmpty(pointY1.Text) || String.IsNullOrEmpty(pointX2.Text) || String.IsNullOrEmpty(pointY2.Text))
                {
                    throw new StringValueException();
                }

                int x1value = int.Parse(pointX1.Text);
                int y1value = int.Parse(pointY1.Text);
                int x2Value = int.Parse(pointX2.Text);
                int y2Value = int.Parse(pointY2.Text);
                var myLine = new Line();
                myLine.Stroke = System.Windows.Media.Brushes.Black;
                myLine.X1 = x1value;
                myLine.Y1 = y1value;
                myLine.X2 = x2Value;
                myLine.Y2 = y2Value;
                myLine.StrokeThickness = 2;
                canvas.Children.Add(myLine);

                if (x1value > canvas.ActualHeight || y1value > canvas.ActualWidth || x2Value > canvas.ActualWidth || y2Value > canvas.ActualWidth)
                {
                    throw new HightValueException();
                }
            }
            catch (HightValueException HValue)
            {
                MessageBox.Show(HValue.Message, "Błąd");
            }
            catch(StringValueException SValue)
            {
                MessageBox.Show(SValue.Message, "Błąd");
            }
        }

        private void Validation(object sender, TextCompositionEventArgs e)
        {
            Regex regex = new Regex("[^0-9]+");
            e.Handled = regex.IsMatch(e.Text);
        }

        private void CheckBoxSiatka_Checked(object sender, RoutedEventArgs e)
        {

                var siatka = new Siatka();
                siatka.ShowDialog();
                int range=0;
                siatka.DataContext = range;

                var w = canvas.Width;
                var h = canvas.Height;

                double rangex = w / range;
                double rangey = h / range;
                Line pion = new Line();
                Line poz = new Line();

                pion.X1 = 20; pion.Y1 = 0;
                pion.X2 = w / 2; pion.Y2 = h;

                poz.X1 = 0; poz.Y1 = h / 2;
                poz.X2 = w; poz.Y2 = h / 2;

                //pionowe
                for (double i = pion.X1 = 0; i <= Math.Floor(rangex); i++)
                {
                    Line l3 = new Line();
                    l3.X1 = 0 + (range * i); l3.Y1 = 0;
                    l3.X2 = 0 + (range * i); l3.Y2 = h;
                    l3.Stroke = System.Windows.Media.Brushes.Black;
                    l3.Opacity = 0.2;
                    l3.StrokeThickness = 2;
                    canvas.Children.Add(l3);
                }

                //poziome
                for (double i = pion.Y1 = 0; i <= Math.Floor(rangey); i++)
                {
                    Line l3 = new Line();
                    l3.X1 = 0; l3.Y1 = 0 + (range * i);
                    l3.X2 = w; l3.Y2 = 0 + (range * i);
                    l3.Stroke = System.Windows.Media.Brushes.Black;
                    l3.StrokeThickness = 2;
                    l3.Opacity = 0.2;
                    canvas.Children.Add(l3);
                }
            
        }

        private void Osie_Checked(object sender, RoutedEventArgs e)
        {
            var w = canvas.Width;
            var h = canvas.Height;

            Line pion = new Line();
            Line poz = new Line();

            pion.X1 = w / 2; pion.Y1 = 0;
            pion.X2 = w / 2; pion.Y2 = h;

            poz.X1 = 0; poz.Y1 = h / 2;
            poz.X2 = w; poz.Y2 = h / 2;

            pion.Stroke = System.Windows.Media.Brushes.Black;
            pion.StrokeThickness = 2;
            canvas.Children.Add(pion);

            poz.Stroke = System.Windows.Media.Brushes.Black;
            poz.StrokeThickness = 2;
            canvas.Children.Add(poz);
            
        }

        private void functionT(object sender, RoutedEventArgs e)
        {

        }

        private void Osie_Unchecked(object sender, RoutedEventArgs e)
        {
            canvas.Children.Clear();
        }

        private void ClearBtn(object sender, RoutedEventArgs e)
        {
            Osie.IsChecked = false;
            canvas.Children.Clear();
        }
    }
}

Strona Siatki

<Window x:Class="WpfApp1.Windows.Siatka"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1.Windows"
        mc:Ignorable="d"
        Title="Siatka" Height="150" Width="300">

    <StackPanel VerticalAlignment="Center" HorizontalAlignment="Center">
        <Label Content="Podaj jednostkę siatki (px):"></Label>
        <TextBox x:Name="jednostka"></TextBox>
        <Button Margin="5" Content="Ok" Click="Button_Click"></Button>
    </StackPanel>
</Window>

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;

namespace WpfApp1.Windows
{
    /// <summary>
    /// Logika interakcji dla klasy Siatka.xaml
    /// </summary>
    public partial class Siatka : Window
    {
        public Siatka()
        {
            InitializeComponent();
        }

        class RangeException : Exception
        {
            public RangeException() : base("Musisz podać jednostke!")
            {

            }
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            Class1 j = new Class1();
            j.Jednostka = Convert.ToInt32(jednostka.Text);
            ((ObservableCollection<Class1>)DataContext).Add(j);
            try
            {
                if (String.IsNullOrEmpty(jednostka.Text))
                {
                    throw new RangeException();
                }
                else
                {
                    this.Close();
                }
            }
            catch(RangeException R) 
            {
                MessageBox.Show(R.Message, "Błąd");
            }
        }
    }
}

Oraz klasa

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WpfApp1
{
    public class Class1
    {
        public int Jednostka { get; set; }
    }
}

Z góry dziękuję za pomoc .

Comments

A nie podaje Ci, w którym miejscu jest ten błąd (plik i numer linii)? Wtedy jest dużo łatwiej namierzyć błąd.

---

Możliwe że się trochę źle wyraziłem. Nie błąd lecz wyjątek i wygląda on tak: i nie za bardzo wiem co z tym zrobić ponieważ pierwszy raz widzę taki wyjątek. Jeśli może Pan pomóc to bardzo byłbym wdzięczny.

Answer 1

Wydaje mi się, że nigdzie wcześniej DataContext nie został utworzony/przypisany. Tzn. nie ma nigdzie DataContext = new ObservableCollection<Class1>() lub przypisania do wartości do DataContext = KKK (gdzie KKK to wcześniej utworzona kolekcja).