I've a problem with two user controls, first of all I've a user control named "Base" and I want to inherit it from another user control named "MyControl" but the "Base" control is a partial class and the user control "MyControl" just have a public class, so I use a partial class in "MyControl", and I use an ElementHost to show "MyControl" but I've the error "Cannot implicity convert type MyControl to System.Windows.UIElement".
I try to add "MyControl" as a Child but it shows that error.
Help!
Edit:
The clases looks like:
public partial class Base : UserControl
{
}
public partial class MyControl : Base
{
}
And I want to do something like this:
public addControl()
{
ElementHost _host = new ElementHost();
_host.Dock = Dockstyle.Fill;
_host.Child = _myControl;
panel.Control.Add(_host);
}
The error is at _host.Child = _myControl;. At this point the object _myControl is initialized.
Does it look something like?
public partial class Base : UIElement
{
}
public class myControl : Base
{
}
I'm not sure what you mean by
and I use an ElementHost
however, my guess is that you are trying to cast myControl as a ElementHost, but it isn't one.
Or myControl doesn't implement something that is required from UIElement.
Let me know if that helps.
Related
I have a main form that acts as a "Wizard" for a bunch of different user controls. I have one user control with relatively basic operations, and I am trying to create a new user control that inherits this basic user control.
However, the base user control has a variable containing the main form (so the user control can access the wizard control functions in the main form). When I create a new "inherited user control" the Designer complains that the reference to the main for has not been set to an instance of the object. I set the reference to the MainForm during runtime when I create an instance of the base user control.
Is there a way to make this work? Below is some simplified code demonstrating my problem.
MainForm.cs:
public partial class MainForm : Form
{
public string exampleString = "From MainForm";
public MainForm()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
BaseControl base = new BaseControl();
base.mainForm = this;
{
}
BaseControl.cs
public partial class BaseControl : UserControl
{
public MainForm mainForm { get; set;}
public TestPanel()
{
InitializeComponent();
string needed = mainForm.exampleString; //Object reference not set to an instance of an object here
}
}
So when I try to create a user control that inherits BaseControl through Solution -> Add -> New Item -> Inherited User Control and select BaseClass, the designer complains of the "Object reference not set to an instance of an object" error at the string needed = mainForm.exampleString line in BaseControl.cs.
Any help with this would be greatly appreciated. Hopefully this is enough information for you to understand what I am trying to do.
Thanks.
The code which you shared will not work, neither at run-time nor in design-time.
You are trying to use mainForm.exampleString in constructor of BaseControl while mainForm will be assigned just after creating an instance of BaseControl.
In such cases, specially when you want to have design-time support, you can derive from ISupportInitialize interface and override BeginInit and EndInit.
Example
The following control implements ISupportInitialize. If you drop an instance of the control on the form, at run-time, it tries to find the parent form and if it was MainForm tries to use public members of the MainForm:
using System.ComponentModel;
using System.Windows.Forms;
public class MyControl : Control, ISupportInitialize
{
public void BeginInit()
{
}
public void EndInit()
{
var parent = this.FindForm() as MainForm;
if (parent != null)
{
//Access to MainForm members
}
}
}
This is just an example that shows how to use ISupportInitialize. In action, it's not a good idea to have a dependency to a specific type of parent form. A better idea as already mentioned in Jimi's comment is relying on interfaces. For example you can have a property of ISomeInterface in your control. The interface should contain the methods or properties which you want to have for the parent of your control. Then implement the interface in some forms. Then after you dropped an instance of your control at run-time or design-time, assign the form to the property.
Well the title should actually explain the problem quite well. Consider I create a new UserControl, however in my application many of those elements share a common code, and they are part of a "subgroup" of user controls.
The logical thing is to "inject" a class between the generated CustomUserControl and UserControl;
Something akin to:
public abstract class CommonCustomControl : UserControl
{
public CommonCustomControl(int v, string other) {
}
}
public partial class CustomUserControl : CommonCustomControl
{
CustomUserControl(int v, string other) : base(v, other) {
}
}
Now the problem with this is, is that the class is only "partially" generated by visual studio. So changing the generated CustomUserControl class gives an error:
"Base class differs from declared in other parts"
How can I prevent this error? While still being able to actually design my user control element in visual studio's gui designer?
I have tried already the answer provided by this question. But it seems to not work at all. (Maybe since that talks about winforms instead of the WPF version)
[TypeDescriptionProvider(typeof(AbstractControlDescriptionProvider<InterfaceHandler, UserControl>))]
public abstract class CommonCustomControl : UserControl
{
private readonly int _v;
private readonly string _other;
public CommonCustomControl(int v, string other) {
_v = v;
_other = other;
}
}
public partial class CustomUserControl : CommonCustomControl
{
public CustomUserControl(int v, string other) : base(v, other) {
}
}
What goes wrong?
You only have your C# code on view here but I'll take a punt at what this might be.
The UserControl you are declaring inherits from a base class.
The UserControl is also a partial class.
Partial classes normally mean that there is other code for this class elsewhere.
The error is stating that the base class is different between the two partial classes.
If you do not have your own second partial class for this UserControl (i.e. it is not just a class, but an actual User Control), then I assume the rest of the definition will be in the XAML.
Depending on how you are implementing your controls:
You may have this:
<UserControl x:Class="NamespaceHere.CustomUserControl"> ... </UserControl>
It should look like this:
<CommonCustomControl x:Class="NamespaceHere.CustomUserControl"> ... </CommonCustomControl>
If not, could you show your XAML too?
Why is this:
public abstract class WindowControls<T> : Window
not possible. I can't seem to figure it out.
public partial class AnglesteelWindow : WindowControls<AngleSteel> {
private UCListView uc;
public AnglesteelWindow() {
InitializeComponent();
uc = new UCListView();
uc.SubmitClick += new EventHandler(ButtonPressed);
this.uc.grid.PreviewMouseLeftButtonUp +=
new System.Windows.Input.MouseButtonEventHandler(
this.MousePressed14<AngleSteel>);
stkTest.Children.Add(uc);
uc.amountLabel.Content = "Milimeter";
uc.grid.ItemsSource = DatabaseLogic.MaterialTable("Anglesteel").DefaultView;
base.Material(uc, "Anglesteel");
}
}
I know how generics work, but don't know why it is not possible to make my AnglesteelWindow derive from WindowControls.
The error it gives me is the following:
Base class of 'Name of the solution' differs from declared in other parts.
When i look at the so called other part it is the following:
public partial class AnglesteelWindow :
WindowControls<AngleSteel> System.Windows.Markup.IComponentConnector {
This is made in the AnglesteelWindow.g.i.cs file. If i remove it from there it makes no difference at all.
Adding on #MichaelMairegger answer, you can reach your goal by creating another non-generic class that inherits from the generic class like this:
public abstract class WindowControlsOfAngleSteel : WindowControls<AngleSteel>
{
}
And make your window class inherit from it like this:
From XAML:
<ns:WindowControlsOfAngleSteel >
</ns:WindowControlsOfAngleSteel >
Where ns is the namespace where WindowControlsOfAngleSteel exists.
In code (optional):
public partial class AnglesteelWindow : WindowControlsOfAngleSteel
{
}
You cannot change the inheritance tree. AnglesteelWindow is partial because it is also declared in AnglesteelWindow.xaml where the root element is Window. If you want to inherit from another class you have to replace there the Window root by your base class.
public class MyDerivedBaseWindow : Window {}
<ns:MyDerivedBaseWindow >
<!-- WindowContent-->
</ns:MyDerivedBaseWindow >
But you cannot use a Generic class in XAML. You have to change your logic that the base-window-class that you want to use as window-root is non-generic.
I use a TabControl in one of my classes. However, I don't want to bloat this class and put all the code in it, as well as all the XAML for the TabItems.
After some Googling I've come up with the UserControl. So I created a UserControl for every TabItem, with the C# code of the TabItem in this UserControl.
The problem here, is that I need to transfer some data from my parent window (the one containing the TabControl) to the UserControls, to correctly display the data needed for that tab.
I created the UserControl in XAML and the code is like this:
<TabItem Name="userTab" Header="Gebruikers" HorizontalAlignment="Stretch">
<local:UserTabControl x:Name="userTabPanel"/>
</TabItem>
This is the constructor code for my UserControl:
public UserTabControl() {
setUsersView(); // NEED DATA FOR THIS
setUserData((User)usersView.SelectedItem);
InitializeComponent();
}
This is the class variable in the UserControl that needs a variable from the parent window: private static Parser m_config;
When I run this, I get a compile error saying :
"Object reference not set to an instance of an object."
pointing to the XAML line where I create my UserControl.
So, the conclusion here is I am yet unable to pass the variable to the UserControl and would like to have some suggestions or hints or guidance on how to do it in this case. Where am I going wrong here in achieving the required functionality ?
Im not sure that its the best way to do so, but for me it worked well.
For start I create CustomUserControl Class that inherit from UserControl with constractor that get his parent Form as an attribute like this:
public partial class CustomUserControl : UserControl
{
MainForm parentForm;
public CustomUserControl(MainForm mainForm)
{
parentForm = mainForm;
}
...
...
private void doSomthing()
{
parentForm.MainFormMember = 1;
}
}
And in the MainForm:
public partial class MainForm : Form
{
private int MainFormMember{ get; set; }
private CustomUserControl customUserControl;
public MainForm()
{
InitializeComponent();
// Create and add the CustomUserControl manually and not from ToolBox
customUserControl = new CustomUserControl(this);
this.Controls.Add(customUserControl);
}
...
...
}
In this way you can access the Form components from the UserControl
Here's my wish to create something abstract in WPF. You've got a main window (called main for example, even if it's not correct we don't care) with two buttons. Those two buttons have the same function : they open a new window, the same for both of them, but with different things inside. So I decided to create an abstract class to rule them like that :
public abstract (partial ?) class A : Window
{
public A()
{
InitializeComponent(); // Not sure about that, it's kinda weird to use it here no ?
}
...
}
public partial class B : A
{
public B()
{
InitializeComponent(); // Since it's already in A I shouldn't have to use it here right ?
}
...
}
public partial class C : A
{
public C()
{
InitializeComponent(); // Same thing here...
}
...
}
Debugging gives me something like : "error CS0263: Partial declarations of 'namespace.B' must not specify different base classes".
Removing 'partial' from A class gives : "error CS0260: Missing partial modifier on declaration of type 'namespace.A'; another partial declaration of this type exists".
I know that 'partial' specifies if a class has another part of her somewhere else (like the xaml file beside the cs one), so I guess the abstract class has to be partial too since it contains my controls. Maybe the B class shouldn't be partial ?
I know (memories) it works with Windows Forms, but there's no xaml files so it's easier, and I didn't find any useful tips. I think I understood that this problem occurs when I don't change something in my xaml file, which doesn't works as simply as "class : abstract class". Maybe the subclass thing ?
Please note that I'm a beginner in WPF apps, so I thank you in advance if your answer is as detailed as possible.
Thanks !
You need to define your base class all in code without using XAML :
Code for class A :
public abstract class A : Window { }
Code for class B :
public partial class B : A
{
public B()
{
InitializeComponent();
}
}
xaml for class B :
<yourNamespace:A x:Class="yourNamespace.B"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:yourNamespace="clr-namespace:yourNamespace"...
A C# partial class is one that is defined over two or more source files. The other 'part' of Window is generated by Visual Studio, and includes things like InitializeComponent()
If you want a base Window class, then it has to be defined entirely in code, and have no XAML component. It will then no longer be a partial class.
public abstract class WindowA : Window
{
// define base methods here
}
Then you can derive WindowB from WindowA:
public partial class WindowB : WindowA
{
public WindowB()
{
InitializeComponent();
}
}
But you also need to do it in the other 'part', i.e. in XAML, so in WindowB's XAML file, the root Window tag needs to be changed to:
<wpfApp:WindowA x:Class="WpfApp.WindowB"
wpfApp:WindowA ="clr-namespace:WpfApp"
(you'll need to change the namespace appropriately)
This will generate the other 'part' deriving from WindowA, so there will be no inconsistency.
The InitializeComponent() method should be called in each derived class' constructor, as it's specific to that class, i.e. in this case, the other 'part' is generated from the XAML, and defines an InitializeComponent() with resourceLocator code that specific to WindowB.