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C# WinForms - Cannot access a control in a handler method

I have a form containing two flow layout panels (FLP), which dynamically have buttons added to them. These buttons are actually a class called tagButton which inherits from Button and I have added a handler in the constructor for the click() method. On click, I want to remove the button from the FLP it is currently in then add it to the other FLP.
Below is a trimmed down version of my code for the tagButton class. Note that the tagButton class is defined inside the of the form class both FLPs are in:
class tagButton : Button
{
public string tag = "";
public bool useTag = false; //tells you which FLP the button is in
public tagButton(String tag, Boolean useTag)
{
this.tag = tag;
this.Text = tag;
this.useTag = useTag;
this.Click += TagButton_Click;
}
private void TagButton_Click(object sender, EventArgs e)
{
tagButton tagButton = (tagButton)sender;
tagButton.useTag = !tagButton.useTag;
if (tagButton.useTag)
{
flowLayoutPanel.Controls.Remove(tagButton);
}
}
}
I'm having problems with the last line:
flowLayoutPanel.Controls.Remove(tagButton);
I can switch it to the following and it works, however there is no way for me to add it to the other FLP. Or at least, not without doing Parent.Parent.Parent.Controls[1]... etc which is clearly a bad idea.
tagButton.Parent.Controls.Remove(tagButton);
I've tried switching different classes and methods to static but nothing I tried worked, the this keyword doesn't seem to work either.

I would recommend having a separate class overriding a parent control that's aware of both FlowLayoutPanels. Then, when your button wants to switch, it can find that custom control in its parents and invoke a custom "switch" function that would move the invoking button from the list it's in to the list it wasn't in.

One of many ways to achieve this outcome is to have MainForm expose a static array of the FlowLayoutPanel candidates as Panels property:
public partial class MainForm : Form
{
public static Control[] Panels { get; private set; }
char _id = (char)64;
public MainForm()
{
InitializeComponent();
Panels = new Control[]{ flowLayoutPanelLeft, flowLayoutPanelRight, };
buttonAddLeft.Click += (sender, e) =>
{
flowLayoutPanelLeft.Controls.Add(new tagButton
{
Height= 50, Width=150,
Name = $"tagButton{++_id}",
Text = $"Button {_id}",
});
};
buttonAddRight.Click += (sender, e) =>
{
flowLayoutPanelRight.Controls.Add(new tagButton
{
Height= 50, Width=150,
Name = $"tagButton{++_id}",
Text = $"Button {_id}",
});
};
}
}
Then, suppose you want to swap between panels when a tagButton gets a right-click (for example).
class tagButton : Button
{
protected override void OnMouseDown(MouseEventArgs e)
{
base.OnMouseDown(e);
if (MouseButtons.Equals(MouseButtons.Right))
{
Control dest;
if(Parent.Name.Contains("Left"))
{
dest = MainForm.Panels.First(_=>_.Name.Contains("Right"));
}
else
{
dest = MainForm.Panels.First(_ => _.Name.Contains("Left"));
}
Parent.Controls.Remove(this);
dest.Controls.Add(this);
}
}
}

Passing an object between two UserControls and a main Form

So I have one main Form that works as the navigation bar and two UserControls that display some controls.
In UserControlsA I have some fields that require to be filled. With that data I create an Object that contains some information. I require to pass that object to UserControlsB so I can display some data there.
My idea was to make three instances of the object, one in the UserControlsA to get the information required for the object, one in the main form to get a "copy" of the object from UserControlsA, and one in UserControlsB that can get the information from the main Form.
However, this seems redundant and doesn't even work. Here's some code:
Main Form:
public partial class main : Form
{
public Object object { get; set; }
public UCA uca;
public UCB ucb;
public Form1()
{
InitializeComponent();
uca = new UCA();
ucb = new UCB();
panel2.Controls.Add(uca);
panel2.Controls.Add(ucb);
ucb.Visible = false;
uca.Visible = true;
}
private void button1_Click(object sender, EventArgs e)
{
ucb.Visible = false;
uca.Visible = true;
}
private void button2_Click(object sender, EventArgs e)
{
ucb.Visible = true;
uca.Visible = false;
}
}
UserControlsA:
public partial class UCA : UserControl
{
public Object object { get; set; }
public UCA()
{
InitializeComponent();
}
private void bUsage_Click(object sender, EventArgs e)
{
//Data is provided
object = new Object(data);
//I use var parent to try and access the object from the main form.
var parent = Parent as Form1;
object = parent.object;
}
}
UsercontrolB:
public partial class UCB : UserControl
{
public Object object { get; set; }
public UCB()
{
InitializeComponent();
}
public void updateData()
{
//I try to assign the object from the main form to this form's object.
var parent = Parent as Form1;
object = parent.object;
}
}
Using var Parent doesn't work. What can I do?

A couple of examples using the INotifyPropertyChanged Interface and an implementation that makes use of standard public events.
Related Documentation:
Windows Forms Data Binding
Change Notification in Windows Forms Data Binding
Interfaces Related to Data Binding
Using INotifyPropertyChanged:
The UserControl exposes a public Property (here, named CustomDataObject, simple string Type in the first example, object in the second. It can another Type of course).
The Property is decorated with the Bindable attribute. The BindingDirection here is more a description of the intent, there's no Template attached to it.
Two other standard Attributes are added:
DefaultValue defines the default value of a Property (the value assigned to the Property when the Control is created). It's used by the Code Generator to determine whether the current value should be serialized: it's not serialized if it matches the value set by the Attribute.
It's also used by the PropertyGrid to show, in bold, a non-default value selection or assignment.
DesignerSerializationVisibility specifies the how the Property should be serialized at design-time. Here, is set to DesignerSerializationVisibility.Visible, to signify that the Property should be serialized.
The INotifyPropertyChanged Interface can be seen as a simplified way to add Property bindings to more than one property, using the same event handler, to notify a change in value.
The default implementation of the Interface simply requires that a a public Event of type PropertyChangedEventHandler is added to the class.
When a Property value is changed, the setter just invokes the Event. There are slightly different ways to perform this action; here I'm using a OnPropertyChanged() method that uses the CallerMemberName Attribute to acquire the name of the Property that calls it. It's fairly common in both WinForms and WPF.
UCA UserControl:
The UserControl (see the visual example), has two Buttons that change the bound CustomDataObject Property value. Their Click action is handled by ButtonsAction_Click.
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows.Forms;
public partial class UCA : UserControl, INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string m_DataObject = string.Empty;
public UCA() => InitializeComponent();
[Bindable(true, BindingDirection.TwoWay), DefaultValue("")]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
public string CustomDataObject {
get => m_DataObject;
set {
if (m_DataObject != value){
m_DataObject = value;
OnPropertyChanged();
}
}
}
private void OnPropertyChanged([CallerMemberName] string propertyName = "") =>
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
private void ButtonsAction_Click(object sender, EventArgs e)
{
var btn = sender as Button;
CustomDataObject = (btn == SomeButton) ? txtInput1.Text : txtInput2.Text;
}
}
UCB UserControl:
This other UserControl is the receiver. It just exposes a public Property (ReceiverDataObject) that will be bound to the CustomDataObject Property of UCA.
The ReceiverDataObject property is also defined as [Bindable], with the intention of making it one-way only. The property doesn't raise any event. It receive a value, stores it in a private Field and sets an internal UI element.
public partial class UCB : UserControl
{
private string m_RecvDataObject = string.Empty;
public UCB() => InitializeComponent();
[Bindable(true, BindingDirection.OneWay)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
public string ReceiverDataObject {
get => m_RecvDataObject;
set {
m_RecvDataObject = value;
txtPresenter.Text = m_RecvDataObject;
}
}
}
Using Standard Events notifications:
You can also generate Property change notifications using standard Events.
The difference is that you need an Event for each Property that should notify changes.
If you already have Event delegates used for this, then it's probably a good choice, since there's very few to add: just call the protected method that raises the Event in the Property setter.
Here, I'm, using the common .Net Event handling, using the EventHandlerList defined by the underlying Component class and exposed by its Events property, to add remove event subscriptions.
The Events are usually raised calling a protected method that has the same name of the Event, except the On prefix.
Here, CustomDataObjectChanged Event => OnCustomDataObjectChanged() method.
You can see this pattern in all standard Controls.
▶ The CustomDataObjectChanged name assigned to the Event is not a choice: this event must have the same name of the Property and the Changed suffix.
This is the pattern, it's enough to just follow it.
UCA UserControl:
public partial class UCA : UserControl
{
private static readonly object Event_CustomDataObjectChanged = new object();
private object m_DataObject = null;
public UCButtonActions() => InitializeComponent();
[Bindable(BindableSupport.Yes, BindingDirection.TwoWay), DefaultValue(null)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
public object CustomDataObject {
get => m_DataObject;
set {
if (m_DataObject != value){
m_DataObject = value;
OnCustomDataObjectChanged(EventArgs.Empty);
}
}
}
public event EventHandler CustomDataObjectChanged {
add {
Events.AddHandler(Event_CustomDataObjectChanged, value);
}
remove {
Events.RemoveHandler(Event_CustomDataObjectChanged, value);
}
}
protected virtual void OnCustomDataObjectChanged(EventArgs e)
{
if (Events[Event_CustomDataObjectChanged] is EventHandler evth) evth(this, e);
}
}
UCB UserControl:
The second UserControl doesn't change. It's just the receiver.
The Form class (or another class used as Handler):
In the Form Constructor, or any other method called after the Form initialization, use the DataBindings property of UCB to link the Properties of the two UserControls:
public SomeForm()
{
InitializeComponent();
ucb1.DataBindings.Add("ReceiverDataObject", uca1, "CustomDataObject",
false, DataSourceUpdateMode.OnPropertyChanged);
}
You can also use a BindingSource to mediate:
BindingSource ucsSource = null;
public SomeForm()
{
InitializeComponent();
ucsSource = new BindingSource(uca1, null);
ucb1.DataBindings.Add("ReceiverDataObject", ucsSource, "CustomDataObject",
false, DataSourceUpdateMode.OnPropertyChanged);
}
Sample functionality:

Maybe you should redesign your data flow. UserControl should not usually make assumptions of what its parent would be, that's why it's a "customized control". It can be a Form1 but not necessary. So you shouldn't do casting like in your example.
To provide the information from A to B, one way is to create public Get/Set methods or properties for those controls. And the main form works with those public members, pseudo-code can be:
class main{
UCA uca;
UCB ucb;
public void RefreshData(){
object data = uca.GetData();
ucb.UpdateData(data);
}
}

So I just learned how to properly use events I guess. Here's how the code looks now:
Main form:
public partial class main : Form
{
public UCA uca;
public UCB ucb;
public delegate void passObject(object source, someObject u);
public Form1()
{
InitializeComponent();
uca = new UCA();
ucb = new UCB();
panel2.Controls.Add(uca);
panel2.Controls.Add(ucb);
ucb.Visible = false;
uca.Visible = true;
}
private void Form1_Load(object sender, EventArgs e)
{
uca.objectRequired += ucb.ucb_objectRequired;
}
private void button1_Click(object sender, EventArgs e)
{
ucb.Visible = false;
uca.Visible = true;
}
private void button2_Click(object sender, EventArgs e)
{
ucb.Visible = true;
uca.Visible = false;
}
}
Usercontrol A:
public partial class UCA : UserControl
{
public someObject o { get; set; }
public event passObject objectRequired;
public UCA()
{
InitializeComponent();
}
private void bUsage_Click(object sender, EventArgs e)
{
//Data is provided
o = new someObject(data);
usageRequired?.Invoke(this, o);
}
}
Usercontrol B:
public partial class UCB : UserControl
{
public SomeObject o { get; set; }
public UCDetails()
{
InitializeComponent();
}
public void ucn_objectRequired(object sender, sObject u)
{
o = u;
//Use the data from the object.
}
}

Passing data between usercontrols c#

It's known that there are some solutions similar to this one, but I can't solve my problem with them.
I have two user controls:
The first one makes a Report object.
The second one shows it.
I have a main Form that links both controls.
These two controls are created in a DLL, and are added to the
main form like this:
//ADDS THE FIRST CONTROL TO THE PANEL CONTROL
myDll.controlUserReport userControlA = new myDll.controlUserReport();
panelControl1.Controls.Add(userControlA);
userControlA.Dock = DockStyle.Left;
//ADDS THE SECOND CONTROL TO THE PANEL CONTROL
myDll.controlDocViewer userControlB = new myDll.controlDocViewer();
panelControl1.Controls.Add(userControlB);
userControlB.Dock = DockStyle.Fill;
How can I pass the Report object, which is created in the first control controlUserReport when I click over a button, to the other user control controlDocViewer to show it?

You should use events for this. In UserControlA declare the event:
//Declare EventHandler outside of class
public delegate void MyEventHandler(object source, Report r);
public class UserControlA
{
public event MyEventHandler OnShowReport;
private void btnShowReport_Click(object sender, Report r)
{
OnShowReport?.Invoke(this, this.Report);
}
}
In UserControlB subscribe to the event and show the report:
public class UserControlB
{
// Do it in Form_Load or so ...
private void init()
{
userControlA.OnShowReport += userControlA_OnShowReport;
}
private void userControlA_OnShowReport(object sender, Report r)
{
// Show the report
this.ShowReport(r);
}
}

the post above is good except init() method should not be in ControlB, but in the parent form, something like this:
public class frmMain : Form
{
private void frmMain_Load(object sender, EventArgs e)
{
// subscribe/glue
userControlA.OnShowReport += userControlB.OnShowReport;
userControlB.OnShowReport += userControlA.OnShowReport;
}
public class UserControlA
{
public event EventHandlerNodeCopy OnDataCopy;
public TreeNode NodeCopied { get; set; }
private void some_method(string z, TreeNode trn)
{
OnDataCopy?.Invoke(this, trn);
...
}
public void frmJsTree_OnDataCopy(object source, TreeNode tn)
{
NodeCopied = tn;
}
public class UserControlB
{
public event EventHandlerNodeCopy OnDataCopy;
public TreeNode NodeCopied { get; set; }
private void another_method(int i, TreeNode trn)
{
OnDataCopy?.Invoke(this, trn);
...
}
public void frmJsTree_OnDataCopy(object source, TreeNode tn)
{
NodeCopied = tn;
}
enter code here

Another approach is using BehaviorSubject (requires System.Reactive). Once the data is added in the BehaviorSubject, all places that subscribe can see the info. A very basic example:
Create a class to represent your data. Ex:
DataService.cs
public static BehaviorSubject<YourDataType> MyAwesomeData { get; } = new BehaviorSubject<YourDataType> (null);
In You UserControlA (maybe in the clickEvent from the button) or whatever:
private void btnShowReport_Click(object sender, MouseButtonEventArgs e)
{
// Do some stuffs to prepare the data...
YourDataType myDataReportPrepared = null; // something;
// Here you update your DataInfo on BehaviorSubject
DataService.MyAwesomeData.OnNext(myDataReportPrepared);
}
Finally every place in your solution that uses subscribe in that Subject will listen to that data, like for example in your UserControlB:
// This will trigger every time MyAwesomeData.OnNext() is executed.
DataService.MyAwesomeData.Subscribe(item =>
{
if (item != null){
// Do something with it...Like populate some Datagrid...
}
});

Is there any way to hide the arrow on a ToolStripMenuItem?

Is there any way to hide the arrow on a ToolStripMenuItem? The arrow is enclosed in the red square.

I've found this is very helpful, you can create your own custom ToolStripRenderer inherits from ToolStripProfessionalRenderer, like this:
public class CustomToolStripRenderer : ToolStripProfessionalRenderer
{
protected override void OnRenderArrow(ToolStripArrowRenderEventArgs e)
{
e.ArrowRectangle = Rectangle.Empty;//Don't draw arrow
base.OnRenderArrow(e);
}
}
//and update the Renderer property of your MenuStrip
menuStrip1.Renderer = new CustomToolStripRenderer();
UPDATE
For your requirement, there are some ways to do but I think this is a good way:
public class CustomToolStripRenderer : ToolStripProfessionalRenderer
{
protected override void OnRenderArrow(ToolStripArrowRenderEventArgs e)
{
if (RenderArrow != null) RenderArrow(this, e);
base.OnRenderArrow(e);
}
public new event ToolStripArrowRenderEventHandler RenderArrow;//This will hide the default RenderArrow event which can't help you change the e argument because the default is fired after the Arrow is rendered.
}
//Now you have to create your own List<ToolStripItem> to contain all the items whose arrows should not be rendered
List<ToolStripItem> ItemsWithoutArrow = new List<ToolStripItem>();
//Add a method to add an item to that list
private void SuppressDrawArrow(ToolStripItem item)
{
if (!ItemsWithoutArrow.Contains(item)) ItemsWithoutArrow.Add(item);
}
//Assign custom ToolStripRenderer for your MenuStrip
menuStrip1.Renderer = new CustomToolStripRenderer();
//Now add a RenderArrow event handler, this RenderArrow event is the new we created in the class CustomToolStripRenderer
((CustomToolStripRenderer)menuStrip1.Renderer).RenderArrow += (s, e) =>
{
if(ItemsWithoutArrow.Contains(e.Item)) e.ArrowRectangle = Rectangle.Empty;
};
//Add some item to the ItemsWithoutArrow to test
SuppressDrawArrow(item1ToolStripMenuItem);
Another solution (I like many solutions to a problem :)
public class CustomToolStripRenderer : ToolStripProfessionalRenderer
{
protected override void OnRenderArrow(ToolStripArrowRenderEventArgs e)
{
if(!itemsWithoutArrow.Contains(e.Item)) base.OnRenderArrow(e);
}
public void SuppressDrawArrow(ToolStripItem item){
if (!itemsWithoutArrow.Contains(item)) itemsWithoutArrow.Add(item);
}
public void AllowDrawArrow(ToolStripItem item){
itemsWithoutArrow.Remove(item);
}
private List<ToolStripItem> itemsWithoutArrow = new List<ToolStripItem>();
}
//Use in code
CustomToolStripRenderer renderer = new CustomToolStripRenderer();
renderer.SuppressDrawArrow(item1ToolStripMenuItem);
menuStrip1.Renderer = renderer;
//This solution fits your requirement (draw or don't draw arrow) but if you also want to change such as ArrowColor, the previous solution would be better.
I've found that we can render it freely with many options. That's great :)

Changing the properties of the active control automatically

Please consider that im a newcomer to c#. After scanning about 700 posts i decided to post one more question:
On my windows form (c#) I have some controls including textboxes, checkboxes and so on.
I want to change the backcolor whenever the controls become active.
I know i could raise 'enter' and 'leave' events for each control to change the corresponding properties but there should be another way.

Simply hook Enter and Leave events - toggling the color in each. Save the last color saved in OnEnter to use in OnLeave
public Form1()
{
InitializeComponent();
var lastColorSaved = Color.Empty;
foreach(Control child in this.Controls)
{
child.Enter += (s, e) =>
{
var control = (Control)s;
lastColorSaved = control.BackColor;
control.BackColor = Color.Red;
};
child.Leave += (s, e) =>
{
((Control)s).BackColor = lastColorSaved;
};
}
}

You customize control classes just like you customize any class, you derive your own class and override the virtual methods. Arbitrarily:
using System;
using System.Drawing;
using System.Windows.Forms;
class MyTextBox : TextBox {
protected override void OnEnter(EventArgs e) {
prevColor = this.BackColor;
this.BackColor = Color.Cornsilk;
base.OnEnter(e);
}
protected override void OnLeave(EventArgs e) {
this.BackColor = prevColor;
base.OnLeave(e);
}
private Color prevColor;
}
Now any MyTextBox you drop on the form will have this behavior without having to implement events. Although there's certainly nothing wrong with using events.

Create a class (eg. ControlColorizer) and in its constructor pass:
1) The backcolor for the 'active control' and save to a internal Color variable
2) a variable length Control array
In the contructor add the same event handler for OnEnter and OnLeave on each control
In the OnEnter event set the backcolor
In the OnLeave event set the standard background color
The advantage is all in the use of the class:
1) Declare a global instance in your form class
2) Initialize in the form contructor after the InitializeComponent.
3) Forget everything else. No other code required
So let me explain everything with code:
This will go in a file called ControlColorizer.cs
public class ControlColorizer
{
private Color _setBColor = SystemColors.Window;
public ControlColor(Color bkg, params Control[] ctls)
{
_setBColor = bkg;
foreach (Control o in ctls)
{
o.Enter += new EventHandler(o_Enter);
o.Leave += new EventHandler(o_Leave);
}
}
private void o_Enter(object sender, EventArgs e)
{
if (sender is Control)
{
Control c = (Control)sender;
c.BackColor = _setBColor;
}
}
private void o_Leave(object sender, EventArgs e)
{
Control c = sender as Control;
c.BackColor = SystemColors.Window;
}
Now, in every form contructor where you need the functionality you have this
ControlColirizer _ccz;
public Form1()
{
InitializeComponent();
// Create an instance of ControlColorizer, pass the background color
// the list of Controls and that's all
_ccz = new ControlColorizer(Color.LightYellow, this.TextBox1,
this.TextBox2, this.TextBox3, this.TextBox4);
}