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Anja Simonsen
NA
41
15.5k
Object reference not set to an instance of an object.
Mar 15 2021 5:21 PM
I have used all day to figure out what happens, and why this errormessage is shown when I link to a view with data from db. But is fine, when only viewing some textstring.
My solution have 5 projects: TheUI, DAL, Model, ViewModel and Views. When run to curser method I can see that the 3 rows from the db goes fine into the Views (UserControls), but when linking on the UI to the specifc UserControl something goes wrong.
I'm pretty sure, there is nothing wrong with DAL and Model, so I'm showing you the 3 other projects.
I'm not cable to attach the file. I do not know why the solution zipped is sice 47mb. If You want code for the other projects, just say so.
The error is in below line in MainWindow.xaml line 110
<views:CategoryView x:Name=
"CategoryView"
Grid.Column=
"0"
Grid.ColumnSpan=
"3"
Grid.Row=
"2"
/>
Best regards
Simsen :)
ViewModel.Account.CategoryViewModel:
using
System;
using
System.Collections.Generic;
using
System.Text;
using
System.Collections.ObjectModel;
using
Model.Account;
using
DAL.Account;
namespace
ViewModel.Account
{
public
class
CategoryViewModel
{
private
Category _selectedCategory;
public
MyICommand DeleteCommand {
get
;
set
; }
public
Category SelectedCategory
{
get
{
return
_selectedCategory;
}
set
{
_selectedCategory = value;
DeleteCommand.RaiseCanExecuteChanged();
}
}
public
CategoryViewModel()
{
LoadCategories();
DeleteCommand =
new
MyICommand(OnDelete, CanDelete);
}
public
ObservableCollection<Category> Categories {
get
;
set
; }
public
void
LoadCategories()
{
DalCategory dalCategory =
new
DalCategory();
ObservableCollection<Category> dalCategories = dalCategory.GetCategories();
Categories = dalCategories;
}
#region Delete
private
void
OnDelete()
{
Categories.Remove(SelectedCategory);
}
private
bool
CanDelete()
{
return
SelectedCategory !=
null
;
}
#endregion
}
}
Views.CategoryView.Account.CategoryView.xaml:
<UserControl x:Class=
"Views.Account.CategoryView"
xmlns=
"http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x=
"http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc=
"http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d=
"http://schemas.microsoft.com/expression/blend/2008"
xmlns:viewModel =
"clr-namespace:ViewModel.Account;assembly=ViewModel"
xmlns:data =
"clr-namespace:Model.Account;assembly=Model"
mc:Ignorable=
"d"
d:DesignHeight=
"450"
d:DesignWidth=
"800"
>
<Grid>
<StackPanel Orientation =
"Horizontal"
>
<ListBox ItemsSource =
"{Binding Mode=OneWay}"
>
<DataTemplate>
<StackPanel Orientation=
"Horizontal"
>
<TextBlock Text=
"{Binding CategoryId}"
/>
<TextBlock Text=
"{Binding CategoryName}"
/>
<TextBlock Text=
"{Binding CategoryIsGlobal}"
/>
<TextBlock Text=
"{Binding ProjectId}"
/>
<TextBlock Text=
"{Binding IsObsolete}"
/>
</StackPanel>
</DataTemplate>
</ListBox>
</StackPanel>
</Grid>
</UserControl>
Views.CategoryView.Account.CategoryView.xaml.cs:
using
System;
using
System.Collections.Generic;
using
System.Linq;
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.Navigation;
using
System.Windows.Shapes;
namespace
Views.Account
{
/// <summary>
/// Interaction logic for CategoryView.xaml
/// </summary>
public
partial
class
CategoryView : UserControl
{
public
CategoryView()
{
InitializeComponent();
this
.DataContext =
new
ViewModel.Account.CategoryViewModel();
string
HereICheckTheDataContextAndItHas3Rows =
""
;
}
}
}
AnsiBug.MainWindow.xaml:
<Window xmlns:syncfusion=
"http://schemas.syncfusion.com/wpf"
x:Name=
"AnsiBug"
x:Class=
"AnsiBug.MainWindow"
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:AnsiBug"
xmlns:views =
"clr-namespace:Views.Account;assembly=Views"
mc:Ignorable=
"d"
Title=
"MainWindow"
Height=
"800"
Width=
"1200"
HorizontalAlignment=
"Center"
VerticalAlignment=
"Center"
WindowStartupLocation=
"CenterScreen"
>
<Window.Resources>
<!--#region Context Menus-->
<!--#region Reports-->
<ContextMenu x:Key=
"cmBtnReports"
>
<MenuItem x:Name=
"BtnTextReports"
Header=
"Tekst rapporter"
/>
<MenuItem x:Name=
"BtnReporsMyBugs"
Header=
"Mine fejl"
/>
<MenuItem x:Name=
"BtnReporsNewBugs"
Header=
"Nye fejl"
/>
<MenuItem x:Name=
"BtnReporsAllBugs"
Header=
"Alle fejl"
/>
<MenuItem x:Name=
"BtnReporsClosedBugs"
Header=
"Lukkede fejl"
/>
<MenuItem x:Name=
"BtnReporsNoAssignedBugs"
Header=
"Ikke tildelte fejl"
/>
</ContextMenu>
<!--#endregion-->
<!--#region Administration-->
<ContextMenu x:Key=
"cmBtnAdministration"
>
<MenuItem x:Name=
"BtnShowUsers"
Header=
"Vis brugere"
/>
<MenuItem x:Name=
"BtnAddUser"
Header=
"Tilføj bruger"
/>
<MenuItem x:Name=
"BtnEditAccount"
Header=
"Ret konto"
/>
<MenuItem x:Name=
"BtnShowProjects"
Header=
"Vis projekter"
/>
<MenuItem x:Name=
"BtnAddProject"
Header=
"Tilføj projekt"
/>
<MenuItem x:Name=
"BtnManagement"
Header=
"Vedligeholdelse"
/>
</ContextMenu>
<!--#endregion-->
<!--#region Preferences-->
<ContextMenu x:Key=
"cmBtnPreferences"
>
<MenuItem x:Name=
"BtnMyInfo"
Header=
"Min info"
/>
</ContextMenu>
<!--#endregion-->
<!--#region Preferences-->
<ContextMenu x:Key=
"cmBtnLists"
>
<MenuItem x:Name=
"BtnMyBugs"
Header=
"Mine fejl"
/>
<MenuItem x:Name=
"BtnNewBugs"
Header=
"Nye fejl"
/>
<MenuItem x:Name=
"BtnAllBugs"
Header=
"Alle fejl"
/>
<MenuItem x:Name=
"BtnUnAssignedBugs"
Header=
"Ikke tildelte fejl"
/>
<MenuItem x:Name=
"BtnClosedBugs"
Header=
"Lukkede fejl"
/>
</ContextMenu>
<!--#endregion-->
<!--#region Projects-->
<ContextMenu x:Key=
"cmBtnProjects"
>
<MenuItem x:Name=
"BtnDashBoard"
Header=
"Dashboard"
/>
<MenuItem x:Name=
"BtnNewBug"
Header=
"Ny fejl"
/>
</ContextMenu>
<!--#endregion-->
<!--#endregion-->
</Window.Resources>
<Window.FocusVisualStyle>
<Style/>
</Window.FocusVisualStyle>
<StackPanel>
<Grid Margin=
"5"
>
<Grid.ColumnDefinitions>
<ColumnDefinition Width=
"250"
/>
<ColumnDefinition Width=
"*"
/>
<ColumnDefinition Width=
"150"
/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height=
"130"
/>
<RowDefinition Height=
"600"
/>
</Grid.RowDefinitions>
<Image Source=
"/Images/Logo/ANSI.gif"
Grid.Row=
"0"
Grid.Column=
"0"
Height=
"100"
/>
<Image Source=
"/Images/Logo/logoBug.gif"
Grid.Row=
"0"
Grid.Column=
"2"
Height=
"100"
/>
<Grid Grid.Column=
"1"
>
<Grid Margin=
"5"
>
<Grid.ColumnDefinitions>
<ColumnDefinition Width=
"*"
/>
<ColumnDefinition Width=
"*"
/>
<ColumnDefinition Width=
"*"
/>
<ColumnDefinition Width=
"*"
/>
<ColumnDefinition Width=
"*"
/>
<ColumnDefinition Width=
"*"
/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height=
"180"
/>
</Grid.RowDefinitions>
<StackPanel Orientation=
"Vertical"
Grid.Row=
"0"
Grid.Column=
"0"
Margin=
"5 0 0 0"
>
<Button x:Name=
"BtnProjects"
Content=
"Projekter"
Style=
"{StaticResource TopMenuButton}"
Click=
"BtnTopMenu_Click"
/>
<Image Source=
"/Images/TopDivider.jpg"
/>
</StackPanel>
<StackPanel Orientation=
"Vertical"
Grid.Row=
"0"
Grid.Column=
"1"
Margin=
"5 0 0 0"
>
<Button x:Name=
"BtnLists"
Content=
"Lister"
Style=
"{StaticResource TopMenuButton}"
Click=
"BtnTopMenu_Click"
/>
<Image Source=
"/Images/TopDivider.jpg"
/>
</StackPanel>
<StackPanel Orientation=
"Vertical"
Grid.Row=
"0"
Grid.Column=
"2"
Margin=
"5 0 0 0"
>
<Button x:Name=
"BtnPreferences"
Content=
"Indstillinger"
Style=
"{StaticResource TopMenuButton}"
Click=
"BtnTopMenu_Click"
/>
<Image Source=
"/Images/TopDivider.jpg"
/>
</StackPanel>
<StackPanel Orientation=
"Vertical"
Grid.Row=
"0"
Grid.Column=
"3"
Margin=
"5 0 0 0"
>
<Button x:Name=
"BtnAdministration"
Content=
"Administration"
Style=
"{StaticResource TopMenuButton}"
Click=
"BtnTopMenu_Click"
/>
<Image Source=
"/Images/TopDivider.jpg"
/>
</StackPanel>
<StackPanel Orientation=
"Vertical"
Grid.Row=
"0"
Grid.Column=
"4"
Margin=
"5 0 0 0"
>
<Button x:Name=
"BtnReports"
Click=
"BtnTopMenu_Click"
Content=
"Rapporter"
Style=
"{StaticResource TopMenuButton}"
/>
<Image Source=
"/Images/TopDivider.jpg"
/>
</StackPanel>
<StackPanel Orientation=
"Vertical"
Grid.Row=
"0"
Grid.Column=
"5"
Margin=
"5 0 0 0"
>
<Button x:Name=
"BtnLogout"
Click=
"BtnLogout_Click"
HorizontalAlignment=
"Right"
HorizontalContentAlignment=
"Right"
Content=
"Log ud"
Style=
"{StaticResource TopMenuButton}"
/>
<Image Source=
"/Images/TopDivider.jpg"
/>
</StackPanel>
</Grid>
</Grid>
<Grid Grid.Row=
"1"
Grid.Column=
"0"
Grid.ColumnSpan=
"3"
Margin=
"25"
>
<views:CategoryView x:Name=
"CategoryView"
Grid.Column=
"0"
Grid.ColumnSpan=
"3"
Grid.Row=
"2"
/>
</Grid>
</Grid>
</StackPanel>
</Window>
And finally AnsiBug.MainWindow.xaml.cs
using
System;
using
System.Collections.Generic;
using
System.Linq;
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.Navigation;
using
System.Windows.Shapes;
namespace
AnsiBug
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public
partial
class
MainWindow : Window
{
public
MainWindow()
{
InitializeComponent();
HideUserControls();
//CategoryView.Visibility = Visibility.Visible;
}
private
void
HideUserControls()
{
//StudentView.Visibility = Visibility.Hidden;
//CategoryView.Visibility = Visibility.Hidden;
}
#region Topmenu knapper
private
void
BtnLogout_Click(
object
sender, RoutedEventArgs e)
{
this
.Close();
}
private
void
BtnTopMenu_Click(
object
sender, RoutedEventArgs e)
{
var button = (Button)sender;
string
btnName =
"cm"
+ button.Name;
ContextMenu cm =
this
.FindResource(btnName)
as
ContextMenu;
cm.PlacementTarget = sender
as
Button;
cm.IsOpen =
true
;
}
#endregion
}
}
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