Develop Reference

Update form when other form is active

I have two Forms ( Form_Graph(Main Form), Form_Setting) and one Setting file. When I click on the Setting button, Form_Setting is opened using ShowDialog().
Form_Setting Contains three buttons OK, Cancel, Apply and setting option. Now the problem is when I change Setting and update setting file and after Click on Apply button, I'm not able to apply this setting to Form_Graph.
(Apply_OnClick saves the new setting in setting files.)
I have tried to refresh Form_Graph using:
Form_Graph obj = new Form_Graph();
Application.OpenForms["Form_Graph"].Refresh();
And also I have debugged it. All Form_Graph code is executing on both the way but hasn't applied the settings.
I know the first way never works because I created one new Form, but what about the second one?
Can anyone have a solution for this?

You don't need to create a new instance of parent in child. The best way to do this normally is to subscribe to events from the child form i.e. Form_Setting. You will need to create an event in the child form as follows:
public event EventHandler SettingsApplied;
public void NotifySettingsApplied(EventArgs e)
{
if(SettingsApplied != null)
SettingsApplied(this, e);
}
public void Apply_OnClick(object sender, EventArgs e)
{
//trigger event here to notify main form
NotifySettingsApplied(e);
}
Then in your parent form, subscribe to this event in the constructor or any other suitable place:
public Form_Graph()
{
fs = new Form_Setting();
fs.SettingsApplied += new EventHandler(fs_SettingsApplied);
}
void fs_SettingsApplied(object sender, EventArgs e)
{
//update your main graph form here
}

All i need to write code on Apply_OnClick
// Get Form_Graph object
Form_Graph objGraph = (Form_Graph)Application.OpenForms["Form_Graph"];
// Create a method in Form_Graph class which apply all setting to components
objGraph.UpdateGraph();
// Now refresh Form_Graph
objGraph.Refresh();

Based on your description and comments, you'll need to reload your form for the colors and graphics. You can do it in one of the 3 ways:
Call InitializeComponent() after you return from your settings dialog. This might be dangerous because InitializeComponent() will do other startup stuff too.
Reload your main form too after returning from settings dialog. You may or may not be able to do that based on the state of your main form.
Collect all the code that updates colors and graphics from InitializeComponent() and move it into a separate function. Call it after InitializeComponent() as well as when returning from your settings dialog.
I think the 3rd one would be the cleanest approach.
Edit
Another and generally much more clean way of doing this is through the use of Application Settings. You just go to your form designer, select your control and choose Application Settings from Properties window. Choose the property that you want to bind to a setting and then choose the corresponding setting from the dropdown. If the setting doesn't already exist, you just click the New button and the designer creates one for you.
These settings automatically get loaded and saved for you. No more manual stuff.
Edit 2
For immediate propagation of settings into control properties, you may need to change the default update event when binding your to your setting. To do that, go to your designer file and look for property binding statements:
this.TextBox1.DataBindings.Add("Text", Project1.Properties.Settings.Default.UserName, ""))
and set them to update immediately upon property change:
this.TextBox1.DataBindings.Add(new System.Windows.Forms.Binding("Text", global::Project1.Properties.Settings.Default, "UserName", true, System.Windows.Forms.DataSourceUpdateMode.OnPropertyChanged));

Set form as Parent throw exception "Top-level control cannot be added to a control"

I want to access variables of a form from another form. On clicking a button inside my Main form, I want to set my Main form as Parent, then bring up another form (child form) wherein I will access variables of the Main form. My click handler is as follow:
private void btnSystem_Click(object sender, EventArgs e)
{
Form_EnterPassword EP = new Form_EnterPassword();
EP.Parent = this; //error: Top-level control cannot be added to a control
EP.ShowDialog();
}
It compiles fine without any error. However, when I run the Main form and click on the System button, it throws me an exception. I do something similar in another code (not mine) with the same button click, and encounter no error (just with setting Main form as Parent).
What am I doing wrong? Is there something in my Main code that cause this?

Best way would be to use EP.ShowDialog(this) and later use Owner property.

You need the EP.TopLevel property to be set to false. It will let you to set a parent to it.
Further reading.
In case you only want to access variables and controls of another form, then maybe you can reach it in other ways, not trough a Parent relationship.

OK,
apparently the way to do it is to call
Form_Child.ShowDialog(this)
and then I can call
FromParent_aVariable = ((Form_Parent)this.Owner).aVariable;
or if I define aVariable in the namespace Properties then
FromParent_aVariable = NameSpace.Properties.Settings.Default.aVariable;
there are two ways.

Form_EnterPassword EP = new Form_EnterPassword();
EP.MdiParent = this;
EP.Show();
try this way, it helps for me. you need to set principalform as isMdicontainer = true at the form properties

I had a similar situation recently.
I was attempting something similar but by controlling the Child Forms from a different class.
Note(s):
You're trying to set the Child Form(s) "TopMost" to something that does not allow it.
In this case the "MdiContainer".
To accomplish this:
• Disable MainForm "isMdiContainer" property (its use is kind of obsolete anyway).
• Set the Form(s) TopMost properties to true.
• You should now be able to accomplish your feature.
**Code Example:**
/* On your Main Form Class */
private void btnSystem_Click(object sender, EventArgs e)
{
// Instantiate the Form_EnterPassword by passing the MainForm
Form_EnterPassword EP = new Form_EnterPassword(this);
EP.Show(); // No longer as modal Form to display in front.
}
/* Under your EnterPassword Form Class */
// Do not create a new Instance of MyMainForm.
// You want to use the same thread as your MainForm
private MyMainForm mainForm;
/* Constructor */
public Form_EnterPassword(MyMainForm form)
{
mainForm = form;
this.Owner = mainForm; // "this" refers to the: EnterPassword Form.
}
Remarks:
The only additional thing that you (may) have to do, (to achieve perfection) is to check the MainForm > WindowState; and create a code block to minimize or bring the Forms to their specific state.
i.e:
if (WindowState == FormWindowState.Minimized)
{ /* Code to Minimize all the Child Forms. */ }
else { /* Code to bring all Forms to their "Normal" State */ }

Writing this way, made the dialog display on the center of the parent form.
Form_Child.StartPosition = FormStartPosition.CenterParent;
Form_Child.ShowDialog(this);

c# - create invisible user control

I need to create a user control in C#.Net, which can be added to the application without being visible - just like the FolderBrowserDialog. It's a new window which I'll be using often so I think this is the right way. The window will be opened by envoking the showDialog-Method as known from the other dialog.
Any Idea?
Thanks and regards,
Daniel

Since all these "invisible" controls derive from Component class, you should start by reading the MSDN article on it: http://msdn.microsoft.com/en-us/library/system.componentmodel.component.aspx.

simply set Visible to false or isn't this what you're asking for ?

A UserControl is by definition not a Form; I think what you really want is a Component. That said, couldn't you really just create a new Form class that has the functionality you want? Whenever you want to display it, create a new instance and call ShowDialog. Or, if you want to preserve state, add an instance as a class member to your parent form, call its Show method whenever you want to display it, and add an event handler to its FormClosing event to check:
if (e.CloseReason == CloseReason.UserClosing)
and, if so,
e.Cancel = true;
Hide();
(This last part is to prevent errors if the user closes the form and then tries to display again after it's been disposed.)

I think more information may be needed, but if your crating a custom user control, the control should have a .Visible property. The follow is an example of how a button can be located on the form but hidden from a user.
button.Visible = true; // shows the button
button.Show(); // Shows the button
button.Visible = false; // hides the button
button.Hide(); // Hides the button
While the button may still be on the form/control, it will not be interactible by the user. You can still perform programmatic control on the button, but essentially it is not a user control while it is 'hidden'. If you want there to be a sort of hidden button that the user can click you will need to do other things to obtain this but It doesn't should like that is what you want.

This show/hide thought process sounds a lot like pains and confusion leftover from classic VB. The old form methods of show and hide, etc., were confusing and often left me as a developer in a position to not know whether an object existed or if was merely invisible. And checking was only trivial if you used On Error Goto to prevent a null reference. So right off I would advise not to think in terms of visibility unless you are doing something with a web page and need to maintain space and state.
First, create a Windows form and add it to your project, assuming that is the type of project that you are describing. Decorate the form with the proper controls, and where applicable, create properties to allow public access to the control values. Also set the DialogResult property of the buttons that either "OK" or "Cancel" the form. Give it an appropriate border style of either Fixed3D or FixedDialog. Maybe also set the property for where you want the form to appear on startup -- center parent, center screen, Windows default, etc. The event handlers for both "OK" and "Cancel" should invoke this.Close(); to close the window.
From the calling point in the code, here's some hypothetical code to get you going in the right direction. Write something like this in the place where you want to invoke your Dialog.
int intResult = 0;
string strResult = null;
MyDialogForm frm = new MyDialogForm();
frm.Title = "Select an Item";
frm.SomeProperty = 0;
frm.SomeOtherProperty = true;
if (frm.ShowDialog() == DialogResult.OK)
{
intResult = frm.Result;
strResult = frm.StringResult;
}
else if (frm.ShowDialog() == DialogResult.Cancel)
{
// User clicked the cancel button. Nothing to do except maybe display a message.
MessageBox.Show("Canceled Task");
}
...
// Somewhere further on down, but within scope, simply repeat
// what you just did, but without having to reinstantiate the
// form Window. But if you make it that far within the same
// scope, this method might be too busy and may need to be
// factored down.
So in short:
Scrap show/hide -- its not a good
practice.
Save the form data without
using an invisible form to save it;
that's the class's job.
If the UI requires a lot of flipping back and
forth between windows, check your
design for other alternatives for
solving the original problem. Maybe a design pattern such as MVC is for you, depending upon the size and complexity of your application.
Sound good?

You can put that control in a Panel. Set the panel height = 0 visible = false when you dont want to show the control.
And do the vice versa when you want to show it.

Derive from Control, not UserControl, and in the constructor set Visible = false.
Also create an event handler in the constructor.
VisibleChanged += new EventHandler(SetVisibleFalse);
Create a method named SetVisibleFalse.
private void SetVisibleFalse(object sender, EventArgs e)
{
if (Visible) Visible = false;
}

User control in windows forms application

I have a simple user control with a text box and label in it. I created public properties to access the text in the textbox when I use the user control in another form.
My problem is the property is returning null value when I call it in the form. Am i missing anything?
My property is as follows::
public partial class UserControl1 : UserControl
{
public UserControl1()
{
InitializeComponent();
}
public string rtnTxtMake
{
get
{
return txtMake.Text;
}
set
{
txtMake.Text = value;
}
}
}
and in the next forms button click event i call the property as follows
UserControl1 Usc = new UserControl1();
string Make = Usc.rtnTxtMake;
MessageBox.Show(Make)

UserControl1 Usc = new UserControl1();
string Make = Usc.rtnTxtMake;
If your user control has by default an empty textbox field, then it seems correct that the above two lines of code would return either null or String.Empty (check via String.IsNullOrEmpty), since you explicitly create a new instance of your user control.
I suppose what you really want is this:
You have inserted a user control into a form in the Designer. Let's call this user control instance ctlUser.
You have a button with a Click event handler. The last few lines of code in your question are from that handler method.
In the handler, you wouldn't create a new instance of your user control (Usc) but refer to the one that you previously inserted into your form, ctlUser. Then things should work as expected.

Your UserControl must be added to the Controls collection of a parent Form/Control before it can be properly initialized. Normally you would not write the code yourself that creates and adds the UserControl.
Instead, first build your project, then go to the Deisgner view of your main form and look at the Toolbox.
Your UserControl name (and an icon) should appear towards the top of the toolbox, and you can simply drag it to the main form. The Windows Forms designer will automatically generate the needed initialization code for you.
You should not create a new instance of your control in your button click event handler. Using the Designer approach to create your control you can simply access the existing instance of your control as follows:
public void button_Click(object sender, EventArgs e)
{
// myUserControl1 has already been created and initialized by the Deisgner generated code
// Note the name 'myUserControl1' is just an example, yours may be different.
string controlText=myUserControl1.rtnTxtMake;
// Or to change the UserControl textbox value
myUserControl1.rtnTxtMake="Testing";
}

What exactly to you mean when you say that the property is returning a null value? Is it actually null, or is your MessageBox simple showing empty?
I quickly duplicated your code and it behaves exactly as expected - the MessageBox shows, but it is empty because the default value of the Text property of the TextBox control is an empty string.
Also, the way you are approaching this is a little unusual.
Firstly, the line:
UserControl1 Usc = new UserControl1();
You do not generally need to instantiate a user control like this. Instead you can drag the control from the toolbox onto the design surface of your form. This will then take care of instantiating and initialising your control for you.
I think that this is actually your problem - when you include the line of code above, you are creating a new instance of the user control, and this is is no way realted to the user control that you have dragged onto the designer.
If you go to the designer view of your form and click on the user control, you should see a properties window somehere. If you do no, then either select it from the View menu, or press F4. In the list of properties, there should be one "Name" this is the programatic name generated for your user control. You can change this here if you want, but when you refer to this control in the rest of the form, this is what you must use.
Secondly, the next two lines:
string Make = Usc.rtnTxtMake;
MessageBox.Show(Make)
You can access the property rtnTxtMake directly. Unless you later need to access the Make string in the rest of your code, then directly accessing the property would usually be considered better style.
MessageBox.Show(userControl.rtnTxtMake);

How to implement the Edit -> Copy menu in c#/.net

How do I implement a Copy menu item in a Windows application written in C#/.NET 2.0?
I want to let the user to mark some text in a control and then select the Copy menu item from an Edit menu in the menubar of the application and then do a Paste in for example Excel.
What makes my head spin is how to first determine which child form is active and then how to find the control that contains the marked text that should be copied to the clipboard.
Help, please.

With the aid of some heavy pair programming a colleague of mine and I came up with this, feel free to refactor.
The code is placed in the main form. The copyToolStripMenuItem_Click method handles the Click event on the Copy menu item in the Edit menu.
/// <summary>
/// Recursively traverse a tree of controls to find the control that has focus, if any
/// </summary>
/// <param name="c">The control to search, might be a control container</param>
/// <returns>The control that either has focus or contains the control that has focus</returns>
private Control FindFocus(Control c)
{
foreach (Control k in c.Controls)
{
if (k.Focused)
{
return k;
}
else if (k.ContainsFocus)
{
return FindFocus(k);
}
}
return null;
}
private void copyToolStripMenuItem_Click(object sender, EventArgs e)
{
Form f = this.ActiveMdiChild;
// Find the control that has focus
Control focusedControl = FindFocus(f.ActiveControl);
// See if focusedControl is of a type that can select text/data
if (focusedControl is TextBox)
{
TextBox tb = focusedControl as TextBox;
Clipboard.SetDataObject(tb.SelectedText);
}
else if (focusedControl is DataGridView)
{
DataGridView dgv = focusedControl as DataGridView;
Clipboard.SetDataObject(dgv.GetClipboardContent());
}
else if (...more?...)
{
}
}

Why not extending the control, so the control itself provides the data which should be copied into the clipboard.
Take a look at ApplicationCommands documentation.

To determine which window is open, you can query the Form.ActiveMDIChild property to get a reference to the currently active window. From there, you can do one of two things:
1) If you create your own custom Form class (FormFoo for example) that has a new public member function GetCopiedData(), then inherit all of your application's child forms from that class, you can just do something like this:
((FormFoo)this.ActiveMDIChild).GetCopiedData();
Assuming the GetCopiedData function will have the form-specific implementation to detect what text should be copied to the clipboard.
or
2) You can use inheritance to detect the type of form that is active, and then do something to get the copied data depending on the type of form:
Form f = this.ActiveMDIChild;
if(f is FormGrid)
{
((FormGrid)f).GetGridCopiedData();
} else if(f is FormText) {
((FormText)f).GetTextCopiedData();
}
etc.
That should get you started with finding the active window and how to implement a copy function. If you need more help copying out of a GridView, it may be best to post another question.

If the form is tabbed and the target control is a DataGridView, it's sometimes possible for the Form's TabControl to be returned as the active control, using the above method, when the DataGridView is right clicked upon.
I got around this by implementing the following handler for my DataGridView:-
private void dataGridView_CellMouseDown(object sender, DataGridViewCellMouseEventArgs e)
{
if (e.Button == MouseButtons.Right)
{
dataGridView.Focus();
dataGridView.CurrentCell = dataGridView[e.ColumnIndex, e.RowIndex];
}
}

It seems to me that you might be better off breaking this into smaller tasks/questions.
You have a few issues you are stuck on from the way it sounds.
You have multiple 'child' windows open. Is this an MDI application?
When an action is performed on one of those child windows, it should fire an event in that window's event handlers. That is your first thing to set up. If this is a datagridview I would suggest a simple test to start. Try trapping the DataGridView.SelectionChanged event. Just throw in something like MessageBox.Show("I copied your datas!"); for now.
This should get you started where you will at least understand how this event will be raised to you.
From here, we will need to know a little more about your datagrid, and the rows and child controls in those rows. Then we can likely create events in the render events that will be raised at the appropriate times, with the appropriate scope.