I almost never used (advanced, or at all) graphical interfaces, or one simple form with simple controls... but this time I've got something a little more complex, and I don't have much experience with GUI.
I have one main form (and possibly more in the future) from which other sub-forms open (and they might have sub-forms of themselves) and I wonder what is, in your opinion, the best way to communicate between them?
I thought of passing the main form as a parameter to the constructors of the sub-forms, but it doesn't seem like a good way, especially if I'm going to need to communicate between other, distinct, sub-forms, not to mention I have to double check the input, or make a few methods, but it seems more like functional programming than object oriented programming...
Perhaps I can:
Create a static class (or Properties.Settings) for global settings. Cons: every change of data is needed to be copied to the class, I'm looking for something a bit more comfortable and elegant.
Use the ugly way of accessing the controls from Application.OpenForms - fixes the problem of passing the main form as parameter. Cons: not very stable.
Do something else I haven't thought of. Suggestions? Cons: don't know what it is yet.
Your constructor idea is probably the most sound method of communication back to the main form. Your sub form would do something like the following:
public class SubForm : Form
{
public SubForm(MainForm parentForm)
{
_parentForm = parentForm;
}
private MainForm _parentForm;
private void btn_UpdateClientName_Click(object sender, EventArgs e)
{
_parentForm.UpdateClientName(txt_ClientName.Text);
}
}
And then you expose public methods on your MainForm:
public class MainForm : Form
{
public void UpdateClientName(string clientName)
{
txt_MainClientName.Text = clientName;
}
}
Alternatively, you can go the other way around and subscribe to events from your SubForms:
public class MainForm : Form
{
private SubForm1 _subForm1;
private SubForm2 _subForm2;
public MainForm()
{
_subForm1 = new SubForm1();
_subForm2 = new SubForm2();
_subForm1.ClientUpdated += new EventHandler(_subForm1_ClientUpdated);
_subForm2.ClientUpdated += new EventHandler(_subForm2_ProductUpdated);
}
private void _subForm1_ClientUpdated(object sender, EventArgs e)
{
txt_ClientName.Text = _subForm1.ClientName; // Expose a public property
}
private void _subForm2_ProductUpdated(object sender, EventArgs e)
{
txt_ProductName.Text = _subForm2.ProductName; // Expose a public property
}
}
A good way is to declare delegates in the form that want to start the communication. You need a delegate and a callback function:
public delegate void SetValueDelegate(string value);
public SetValueDelegate SetValueCallback;
Another form can then attach to this delegate. At that moment both forms have to know each other, but not after that moment:
firstForm.SetValueCallback += new SetValueDelegate(secondForm.SetValueFunction);
The second form has to declare a function that matches the delegate definition:
public void SetValueFunction(string value)
{
// do something
}
Now the first form can use the delegate to use the function of the second form (and all other forms or classes that were attached to the delegate:
SetValueCallback(txtParam.Text);
Edit: made an complete example
using System;
namespace DelegateTest
{
public delegate void SetValueDelegate(string value);
public class Class1
{
public SetValueDelegate SetValueCallBack;
public void Test()
{
if(SetValueCallBack != null)
{
SetValueCallBack("Hello World!");
}
}
}
public class Class2
{
public void SetValueFunction(string value)
{
Console.WriteLine(value);
}
}
public class Launcher
{
public static void Main(string[] args)
{
Class1 c1 = new Class1();
Class2 c2 = new Class2();
c1.SetValueCallBack += new SetValueDelegate(c2.SetValueFunction);
c1.Test();
}
}
}
The most flexible, scalable (and IMHO the most professional) way to do it is to use CAB (Composite Application Block). In simple terms CAB is a set of 2-3 assemblies that implement a lot of plumbing required to make complex UI applications the right way and it exposes this plumbing to the user of the library in a nice way. Among others it has a very nice event and command (as in command pattern) system.
The downside: requires some time to learn and not very trivial to grasp.
Here is a comprehensive (but easy to understand) tutorial that will help you make the learning easier.
You can use the built in Tag property of the form which is an "object" class.
public Form1()
{
(ComplicatedDataStructure)Tag = new ComplicatedDataStracture();
}
.
.
form1 = new Form1();
.
.
form2 = new Form2();
.
.
form2.Tag = form1.Tag;
so form2.Tag is equals to "ComplicatedDataStracture" object;
Related
I have two forms, one is the main form and the other is an options form. So say for example that the user clicks on my menu on the main form: Tools -> Options, this would cause my options form to be shown.
My question is how can I send data from my options form back to my main form? I know I could use properties, but I have a lot of options and this seems like an tedious odd thing to do.
So what is the best way?
Form1 triggers Form2 to open. Form2 has overloaded constructor which takes calling form as argument and provides its reference to Form2 members. This solves the communication problem. For example I've exposed Label Property as public in Form1 which is modified in Form2.
With this approach you can do communication in different ways.
Download Link for Sample Project
//Your Form1
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Form2 frm = new Form2(this);
frm.Show();
}
public string LabelText
{
get { return Lbl.Text; }
set { Lbl.Text = value; }
}
}
//Your Form2
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
private Form1 mainForm = null;
public Form2(Form callingForm)
{
mainForm = callingForm as Form1;
InitializeComponent();
}
private void Form2_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
this.mainForm.LabelText = txtMessage.Text;
}
}
(source: ruchitsurati.net)
(source: ruchitsurati.net)
In the comments to the accepted answer, Neeraj Gulia writes:
This leads to tight coupling of the forms Form1 and Form2, I guess instead one should use custom events for such kind of scenarios.
The comment is exactly right. The accepted answer is not bad; for simple programs, and especially for people just learning programming and trying to get basic scenarios to work, it's a very useful example of how a pair of forms can interact.
However, it's true that the coupling that example causes can and should be avoided, and that in the particular example, an event would accomplish the same thing in a general-purpose, decoupled way.
Here's an example, using the accepted answer's code as the baseline:
Form1.cs:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Form2 frm = new Form2();
frm.Button1Click += (s1, e1) => Lbl.Text = ((Form2)s1).Message;
frm.Show();
}
}
The above code creates a new instance of Form2, and then before showing it, adds an event handler to that form's Button1Click event.
Note that the expression (s1, e1) => Lbl.Text = ((Form2)s1).Message is converted automatically by the compiler to a method that looks something similar to (but definitely not exactly like) this:
private void frm_Message(object s1, EventArgs e1)
{
Lbl.Text = ((Form2)s1).Message;
}
There are actually lots of ways/syntaxes to implement and subscribe the event handler. For example, using an anonymous method as the above, you don't really need to cast the sender parameter; instead you can just use the frm local variable directly: (s1, e1) => Lbl.Text = frm.Message.
Going the other way, you don't need to use an anonymous method. You could in fact just declare a regular method just like the compiler-generated one I show above, and then subscribe that method to the event: frm.Button1Click += frm_Message; (where you have of course used the name frm_Message for the method, just as in my example above).
Regardless of how you do it, of course you will need for Form2 to actually implement that Button1Click event. That's very simple…
Form2.cs:
public partial class Form2 : Form
{
public event EventHandler Button1Click;
public string Message { get { return txtMessage.Text; } }
public Form2()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
EventHandler handler = Button1Click;
if (handler != null)
{
handler(this, EventArgs.Empty);
}
}
}
In addition to the event, I've also declared a property Message that exposes the Text property (and only the Text property, and only as read-only in fact) of the txtMessage control. This allows the subscriber to the event to get the value and do whatever it needs to with it.
Note that all that the event does is to alert the subscriber that the button has in fact been clicked. It's up to the subscriber to decide how to interpret or react to that event (e.g. by retrieving the value of the Message property and assigning it to something).
Alternatively, you could in fact deliver the text along with the event itself, by declaring a new EventArgs sub-class and using that for the event instead:
public class MessageEventArgs : EventArgs
{
public string Message { get; private set; }
public MessageEventArgs(string message)
{
Message = message;
}
}
public partial class Form2 : Form
{
public event EventHandler<MessageEventArgs> Button1Click;
public Form2()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
EventHandler handler = Button1Click;
if (handler != null)
{
handler(this, new MessageEventArgs(txtMessage.Text));
}
}
}
Then the subscriber can just retrieve the message value directly from the event object:
frm.Button1Click += (sender, e) => Lbl.Text = e.Message;
The important thing note in all of the above variations is that at no point does the class Form2 need to know anything about Form1. Having Form1 know about Form2 is unavoidable; after all, that's the object that will create a new Form2 instance and use it. But the relationship can be asymmetrical, with Form2 being usable by any object that needs the features it offers. By exposing the functionality as an event (and optionally with a property), it makes itself useful without limiting its usefulness to only the Form1 class.
The best in this case would be to have some OptionsService class/interface that is accessible via IServiceProvider.
Just add an event when something changes, and the rest of the app can respond to it.
There are lots of ways to perform communication between two Forms.
Some of them have already been explained to you. I am showing you the other way around.
Assuming you have to update some settings from the child form to the parent form. You can make use of these two ways as well :
Using System.Action (Here you simply pass the main forms function as the parameter to the child form like a callback function)
OpenForms Method ( You directly call one of your open forms)
Using System.Action
You can think of it as a callback function passed to the child form.
// -------- IN THE MAIN FORM --------
// CALLING THE CHILD FORM IN YOUR CODE LOOKS LIKE THIS
Options frmOptions = new Options(UpdateSettings);
frmOptions.Show();
// YOUR FUNCTION IN THE MAIN FORM TO BE EXECUTED
public void UpdateSettings(string data)
{
// DO YOUR STUFF HERE
}
// -------- IN THE CHILD FORM --------
Action<string> UpdateSettings = null;
// IN THE CHILD FORMS CONSTRUCTOR
public Options(Action<string> UpdateSettings)
{
InitializeComponent();
this.UpdateSettings = UpdateSettings;
}
private void btnUpdate_Click(object sender, EventArgs e)
{
// CALLING THE CALLBACK FUNCTION
if (UpdateSettings != null)
UpdateSettings("some data");
}
OpenForms Method
This method is easy (2 lines). But only works with forms that are open.
All you need to do is add these two lines where ever you want to pass some data.
Main frmMain = (Main)Application.OpenForms["Main"];
frmMain.UpdateSettings("Some data");
Properties is one option, shared static class - another option, events - another option...
You might try AutoMapper. Keep your options in a separate class and then use AutoMapper to shuttle the data between the class and the form.
Create a Class and put all your properties inside the class .. Create a Property in the parent class and set it from your child (options) form
You can have a function in Form B like so:
public SettingsResults GetNewSettings()
{
if(this.ShowDialog() == DialogResult.Ok)
{
return new SettingsResult { ... };
}
else
{
return null;
}
}
And you can call it like this:
...
using(var fb = new FormB())
{
var s = fb.GetNewSettings();
...
// Notify other parts of the application that settings have changed.
}
MVC, MVP, MVVM -- slight overkill for someone admittedly saying they want tutorials. Those are theories that have entire courses dedicated to them.
As already posted, passing an object around is probably easiest. If treating a class as an object (interchangeable in this sense) is new, then you may want to spend another 2-4 weeks figuring out properties and constructors and such.
I'm not a C# master by any means, but these concepts need to be pretty concrete if you want to go much further beyond passing values between two forms (also classes/objects in their own right). Not trying to be mean here at all, it just sounds like you're moving from something like VB6 (or any language with globals) to something far more structured.
Eventually, it will click.
This is probably sidestepping your problem a little bit, but my settings dialog uses the Application Settings construct. http://msdn.microsoft.com/en-us/library/k4s6c3a0.aspx
I can't find a good example that's similar to how I do it (which is actually having an actual class+object), but this covers another way of doing it:
Reading default application settings in C#
A form is a class, just like any other class. Add some public variables to your form class and set them when they click the button to close the form (technically they are just hiding it).
A VB.NET example, but you'll get the idea -
In your OptionsForm class:
Public Option1 as String = ""
etc. Set them when they hit the "Ok" button.
So in your main form, when they hit the "options" button - you create your options form:
OptionsForm.ShowDialog()
when it exits, you harvest your option settings from the public variables on the form:
option1 = OptionsForm.Option1
etc.
The best way to deal with communication between containers is to implement an observer class
The observer pattern is a software design pattern in which an object, called the subject, maintains a list of its dependents, called observers, and notifies them automatically of any state changes, usually by calling one of their methods.
(Wikipedia)
the way i do this is creating an Observer class, and inside it write something like this:
1 public delegate void dlFuncToBeImplemented(string signal);
2 public static event dlFuncToBeImplemented OnFuncToBeImplemented;
3 public static void FuncToBeImplemented(string signal)
4 {
5 OnFuncToBeImplemented(signal);
6 }
so basically: the first line says that there would be a function that somebody else will implement
the second line is creating an event that occurs when the delegated function will call
and the third line is the creation of the function that calls the event
so in your UserControl, you should add a function like this:
private void ObserverRegister()//will contain all observer function registration
{
Observer.OnFuncToBeImplemented += Observer_OnFuncToBeImplemented;
/*and more observer function registration............*/
}
void Observer_OnFuncToBeImplemented(string signal)//the function that will occur when FuncToBeImplemented(signal) will call
{
MessageBox.Show("Signal "+signal+" received!", "Atention!", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
}
and in your Form you should do something like:
public static int signal = 0;
public void button1_Click(object sender, EventArgs e)
{
Observer.FuncToBeImplemented(signal);//will call the event in the user control
}
and now, you can register this function to a whole bunch of other controls and containers and they will all get the signal
I hope this would help :)
I have a windows form app with 2 forms, and I need to press a button in form one to go to form 2(this is done already) then form 2 will be able to create an object using the add customer method to add to the system. My question is:
1)if I create an Object in Form 2, how could other forms(form3,form4 etc.) have access to this object? As far as I have learned, I can only call the method through an object.
2)if I created an object in Form1, and other forms inherited from form 1, will this object still work in other forms?
3)Objects can be inhereited or not? is this a good practice in real world?
4) How to allow different forms using one object different method?
A static field or property as suggested in zdimension's answer is possible, of course, but it shouldn't be your first option. There are lots of ways to pass data between forms, and it depends on your application which one is best. For example, one way of doing it is:
class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
public AirlineCoordinator Coordinator {get; set;}
...
}
class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
public AirlineCoordinator Coordinator {get; set;}
private void Form1_Load(object sender, EventArgs e)
{
this.Coordinator = new AirlineCoordinator(...);
...
}
...
private void ShowForm2Button_Click(object sender, EventArgs e)
{
using(var form2 = new Form2())
{
form2.Coordinator = this.Coordinator;
form2.ShowDialog(this);
}
}
}
In this hypothetical example, Form1 has a button ShowForm2Button; clicking on this button shows Form2 using the same AirlineCoordinator as is used by Form1.
The usual way to make something available to "everyone" is to use a static field, like this:
public class GlobalStuff
{
public static MyType SomeVariable;
}
Here, the GlobalStuff obviously only ever contains global things, so you could consider making it static too to indicate it will never be instanciated.
Here's what MSDN say about it:
Use a static class as a unit of organization for methods not associated with particular objects. Also, a static class can make your implementation simpler and faster because you do not have to create an object in order to call its methods. It is useful to organize the methods inside the class in a meaningful way, such as the methods of the Math class in the System namespace.
I am attempting to use Delegates to pass data between two Windows. I want a list of People to appear when the user clicks a button on the main Window, this will then allow the user to select a Person. After doing this it will fill in a TextBox on the original form with the Person name.
I started off much simpler than this however to get my head around Delegates and I'm having issues understanding how to call methods on separate Windows with the Delegates. This is what I have attempted so far;
The method on the main Window that waits for a string (ShowMessage);
public static DelegateTestWindow.TestDelegate ShowDelegateMessage(string message)
{
MessageBox.Show(message);
return null;
}
The second Window that contains the Delegate;
public partial class DelegateTestWindow : Window
{
public delegate string TestDelegate();
public DelegateTestWindow()
{
InitializeComponent();
}
private void TestDelegateClick(object sender, RoutedEventArgs e)
{
var tDelegate = new TestDelegate(CompanyManagement.ShowDelegateMessage("Test"));
this.Close();
}
}
This does show a message saying "Test" however it also throws an Exception after doing so: Delegate to an instance method cannot have null 'this'.
The method on the MainWindow especially does not look correct to me, however after trying different options this is the closest I've got to a working Delegate. Could someone explain where I have (clearly) gone wrong here and how I can improve the system I've got now?
Like Mat linked, events are a special kind of delegate, which is probably what you are looking for.
I've written a small example, hopefully this is enough for you to resolve your issue.
public partial class Form1 : Form
{
public event EventHandler PersonSelected;
public String PersonName { get; set; }
public Form1()
{
InitializeComponent();
PersonName = "Person's name";
}
protected override void OnClick(EventArgs e)
{
Form2 form2 = new Form2(this);
form2.Show();
PersonSelected(this, EventArgs.Empty);
}
}
public partial class Form2 : Form
{
public Form2(Form1 form)
{
InitializeComponent();
form.PersonSelected += (sender, args) =>
{
Form1 form1 = sender as Form1;
if(form1 != null)
textBox1.Text = form1.PersonName;
};
}
}
Now, this can be done differently, and better than this, however I think this should suffice. When you get this to work, I recommend you look into another way of doing this. Typically you will create a PersonEventArgs class which inherits from EventArgs. This class then holds a reference to the person. Here is a decent link with an example:
https://msdn.microsoft.com/en-us/library/system.eventargs(v=vs.110).aspx
Good luck :)
I have two forms, one is the main form and the other is an options form. So say for example that the user clicks on my menu on the main form: Tools -> Options, this would cause my options form to be shown.
My question is how can I send data from my options form back to my main form? I know I could use properties, but I have a lot of options and this seems like an tedious odd thing to do.
So what is the best way?
Form1 triggers Form2 to open. Form2 has overloaded constructor which takes calling form as argument and provides its reference to Form2 members. This solves the communication problem. For example I've exposed Label Property as public in Form1 which is modified in Form2.
With this approach you can do communication in different ways.
Download Link for Sample Project
//Your Form1
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Form2 frm = new Form2(this);
frm.Show();
}
public string LabelText
{
get { return Lbl.Text; }
set { Lbl.Text = value; }
}
}
//Your Form2
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
private Form1 mainForm = null;
public Form2(Form callingForm)
{
mainForm = callingForm as Form1;
InitializeComponent();
}
private void Form2_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
this.mainForm.LabelText = txtMessage.Text;
}
}
(source: ruchitsurati.net)
(source: ruchitsurati.net)
In the comments to the accepted answer, Neeraj Gulia writes:
This leads to tight coupling of the forms Form1 and Form2, I guess instead one should use custom events for such kind of scenarios.
The comment is exactly right. The accepted answer is not bad; for simple programs, and especially for people just learning programming and trying to get basic scenarios to work, it's a very useful example of how a pair of forms can interact.
However, it's true that the coupling that example causes can and should be avoided, and that in the particular example, an event would accomplish the same thing in a general-purpose, decoupled way.
Here's an example, using the accepted answer's code as the baseline:
Form1.cs:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Form2 frm = new Form2();
frm.Button1Click += (s1, e1) => Lbl.Text = ((Form2)s1).Message;
frm.Show();
}
}
The above code creates a new instance of Form2, and then before showing it, adds an event handler to that form's Button1Click event.
Note that the expression (s1, e1) => Lbl.Text = ((Form2)s1).Message is converted automatically by the compiler to a method that looks something similar to (but definitely not exactly like) this:
private void frm_Message(object s1, EventArgs e1)
{
Lbl.Text = ((Form2)s1).Message;
}
There are actually lots of ways/syntaxes to implement and subscribe the event handler. For example, using an anonymous method as the above, you don't really need to cast the sender parameter; instead you can just use the frm local variable directly: (s1, e1) => Lbl.Text = frm.Message.
Going the other way, you don't need to use an anonymous method. You could in fact just declare a regular method just like the compiler-generated one I show above, and then subscribe that method to the event: frm.Button1Click += frm_Message; (where you have of course used the name frm_Message for the method, just as in my example above).
Regardless of how you do it, of course you will need for Form2 to actually implement that Button1Click event. That's very simple…
Form2.cs:
public partial class Form2 : Form
{
public event EventHandler Button1Click;
public string Message { get { return txtMessage.Text; } }
public Form2()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
EventHandler handler = Button1Click;
if (handler != null)
{
handler(this, EventArgs.Empty);
}
}
}
In addition to the event, I've also declared a property Message that exposes the Text property (and only the Text property, and only as read-only in fact) of the txtMessage control. This allows the subscriber to the event to get the value and do whatever it needs to with it.
Note that all that the event does is to alert the subscriber that the button has in fact been clicked. It's up to the subscriber to decide how to interpret or react to that event (e.g. by retrieving the value of the Message property and assigning it to something).
Alternatively, you could in fact deliver the text along with the event itself, by declaring a new EventArgs sub-class and using that for the event instead:
public class MessageEventArgs : EventArgs
{
public string Message { get; private set; }
public MessageEventArgs(string message)
{
Message = message;
}
}
public partial class Form2 : Form
{
public event EventHandler<MessageEventArgs> Button1Click;
public Form2()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
EventHandler handler = Button1Click;
if (handler != null)
{
handler(this, new MessageEventArgs(txtMessage.Text));
}
}
}
Then the subscriber can just retrieve the message value directly from the event object:
frm.Button1Click += (sender, e) => Lbl.Text = e.Message;
The important thing note in all of the above variations is that at no point does the class Form2 need to know anything about Form1. Having Form1 know about Form2 is unavoidable; after all, that's the object that will create a new Form2 instance and use it. But the relationship can be asymmetrical, with Form2 being usable by any object that needs the features it offers. By exposing the functionality as an event (and optionally with a property), it makes itself useful without limiting its usefulness to only the Form1 class.
The best in this case would be to have some OptionsService class/interface that is accessible via IServiceProvider.
Just add an event when something changes, and the rest of the app can respond to it.
There are lots of ways to perform communication between two Forms.
Some of them have already been explained to you. I am showing you the other way around.
Assuming you have to update some settings from the child form to the parent form. You can make use of these two ways as well :
Using System.Action (Here you simply pass the main forms function as the parameter to the child form like a callback function)
OpenForms Method ( You directly call one of your open forms)
Using System.Action
You can think of it as a callback function passed to the child form.
// -------- IN THE MAIN FORM --------
// CALLING THE CHILD FORM IN YOUR CODE LOOKS LIKE THIS
Options frmOptions = new Options(UpdateSettings);
frmOptions.Show();
// YOUR FUNCTION IN THE MAIN FORM TO BE EXECUTED
public void UpdateSettings(string data)
{
// DO YOUR STUFF HERE
}
// -------- IN THE CHILD FORM --------
Action<string> UpdateSettings = null;
// IN THE CHILD FORMS CONSTRUCTOR
public Options(Action<string> UpdateSettings)
{
InitializeComponent();
this.UpdateSettings = UpdateSettings;
}
private void btnUpdate_Click(object sender, EventArgs e)
{
// CALLING THE CALLBACK FUNCTION
if (UpdateSettings != null)
UpdateSettings("some data");
}
OpenForms Method
This method is easy (2 lines). But only works with forms that are open.
All you need to do is add these two lines where ever you want to pass some data.
Main frmMain = (Main)Application.OpenForms["Main"];
frmMain.UpdateSettings("Some data");
Properties is one option, shared static class - another option, events - another option...
You might try AutoMapper. Keep your options in a separate class and then use AutoMapper to shuttle the data between the class and the form.
Create a Class and put all your properties inside the class .. Create a Property in the parent class and set it from your child (options) form
You can have a function in Form B like so:
public SettingsResults GetNewSettings()
{
if(this.ShowDialog() == DialogResult.Ok)
{
return new SettingsResult { ... };
}
else
{
return null;
}
}
And you can call it like this:
...
using(var fb = new FormB())
{
var s = fb.GetNewSettings();
...
// Notify other parts of the application that settings have changed.
}
MVC, MVP, MVVM -- slight overkill for someone admittedly saying they want tutorials. Those are theories that have entire courses dedicated to them.
As already posted, passing an object around is probably easiest. If treating a class as an object (interchangeable in this sense) is new, then you may want to spend another 2-4 weeks figuring out properties and constructors and such.
I'm not a C# master by any means, but these concepts need to be pretty concrete if you want to go much further beyond passing values between two forms (also classes/objects in their own right). Not trying to be mean here at all, it just sounds like you're moving from something like VB6 (or any language with globals) to something far more structured.
Eventually, it will click.
This is probably sidestepping your problem a little bit, but my settings dialog uses the Application Settings construct. http://msdn.microsoft.com/en-us/library/k4s6c3a0.aspx
I can't find a good example that's similar to how I do it (which is actually having an actual class+object), but this covers another way of doing it:
Reading default application settings in C#
A form is a class, just like any other class. Add some public variables to your form class and set them when they click the button to close the form (technically they are just hiding it).
A VB.NET example, but you'll get the idea -
In your OptionsForm class:
Public Option1 as String = ""
etc. Set them when they hit the "Ok" button.
So in your main form, when they hit the "options" button - you create your options form:
OptionsForm.ShowDialog()
when it exits, you harvest your option settings from the public variables on the form:
option1 = OptionsForm.Option1
etc.
The best way to deal with communication between containers is to implement an observer class
The observer pattern is a software design pattern in which an object, called the subject, maintains a list of its dependents, called observers, and notifies them automatically of any state changes, usually by calling one of their methods.
(Wikipedia)
the way i do this is creating an Observer class, and inside it write something like this:
1 public delegate void dlFuncToBeImplemented(string signal);
2 public static event dlFuncToBeImplemented OnFuncToBeImplemented;
3 public static void FuncToBeImplemented(string signal)
4 {
5 OnFuncToBeImplemented(signal);
6 }
so basically: the first line says that there would be a function that somebody else will implement
the second line is creating an event that occurs when the delegated function will call
and the third line is the creation of the function that calls the event
so in your UserControl, you should add a function like this:
private void ObserverRegister()//will contain all observer function registration
{
Observer.OnFuncToBeImplemented += Observer_OnFuncToBeImplemented;
/*and more observer function registration............*/
}
void Observer_OnFuncToBeImplemented(string signal)//the function that will occur when FuncToBeImplemented(signal) will call
{
MessageBox.Show("Signal "+signal+" received!", "Atention!", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
}
and in your Form you should do something like:
public static int signal = 0;
public void button1_Click(object sender, EventArgs e)
{
Observer.FuncToBeImplemented(signal);//will call the event in the user control
}
and now, you can register this function to a whole bunch of other controls and containers and they will all get the signal
I hope this would help :)
I have two forms, one is the main form and the other is an options form. So say for example that the user clicks on my menu on the main form: Tools -> Options, this would cause my options form to be shown.
My question is how can I send data from my options form back to my main form? I know I could use properties, but I have a lot of options and this seems like an tedious odd thing to do.
So what is the best way?
Form1 triggers Form2 to open. Form2 has overloaded constructor which takes calling form as argument and provides its reference to Form2 members. This solves the communication problem. For example I've exposed Label Property as public in Form1 which is modified in Form2.
With this approach you can do communication in different ways.
Download Link for Sample Project
//Your Form1
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Form2 frm = new Form2(this);
frm.Show();
}
public string LabelText
{
get { return Lbl.Text; }
set { Lbl.Text = value; }
}
}
//Your Form2
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
private Form1 mainForm = null;
public Form2(Form callingForm)
{
mainForm = callingForm as Form1;
InitializeComponent();
}
private void Form2_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
this.mainForm.LabelText = txtMessage.Text;
}
}
(source: ruchitsurati.net)
(source: ruchitsurati.net)
In the comments to the accepted answer, Neeraj Gulia writes:
This leads to tight coupling of the forms Form1 and Form2, I guess instead one should use custom events for such kind of scenarios.
The comment is exactly right. The accepted answer is not bad; for simple programs, and especially for people just learning programming and trying to get basic scenarios to work, it's a very useful example of how a pair of forms can interact.
However, it's true that the coupling that example causes can and should be avoided, and that in the particular example, an event would accomplish the same thing in a general-purpose, decoupled way.
Here's an example, using the accepted answer's code as the baseline:
Form1.cs:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Form2 frm = new Form2();
frm.Button1Click += (s1, e1) => Lbl.Text = ((Form2)s1).Message;
frm.Show();
}
}
The above code creates a new instance of Form2, and then before showing it, adds an event handler to that form's Button1Click event.
Note that the expression (s1, e1) => Lbl.Text = ((Form2)s1).Message is converted automatically by the compiler to a method that looks something similar to (but definitely not exactly like) this:
private void frm_Message(object s1, EventArgs e1)
{
Lbl.Text = ((Form2)s1).Message;
}
There are actually lots of ways/syntaxes to implement and subscribe the event handler. For example, using an anonymous method as the above, you don't really need to cast the sender parameter; instead you can just use the frm local variable directly: (s1, e1) => Lbl.Text = frm.Message.
Going the other way, you don't need to use an anonymous method. You could in fact just declare a regular method just like the compiler-generated one I show above, and then subscribe that method to the event: frm.Button1Click += frm_Message; (where you have of course used the name frm_Message for the method, just as in my example above).
Regardless of how you do it, of course you will need for Form2 to actually implement that Button1Click event. That's very simple…
Form2.cs:
public partial class Form2 : Form
{
public event EventHandler Button1Click;
public string Message { get { return txtMessage.Text; } }
public Form2()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
EventHandler handler = Button1Click;
if (handler != null)
{
handler(this, EventArgs.Empty);
}
}
}
In addition to the event, I've also declared a property Message that exposes the Text property (and only the Text property, and only as read-only in fact) of the txtMessage control. This allows the subscriber to the event to get the value and do whatever it needs to with it.
Note that all that the event does is to alert the subscriber that the button has in fact been clicked. It's up to the subscriber to decide how to interpret or react to that event (e.g. by retrieving the value of the Message property and assigning it to something).
Alternatively, you could in fact deliver the text along with the event itself, by declaring a new EventArgs sub-class and using that for the event instead:
public class MessageEventArgs : EventArgs
{
public string Message { get; private set; }
public MessageEventArgs(string message)
{
Message = message;
}
}
public partial class Form2 : Form
{
public event EventHandler<MessageEventArgs> Button1Click;
public Form2()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
EventHandler handler = Button1Click;
if (handler != null)
{
handler(this, new MessageEventArgs(txtMessage.Text));
}
}
}
Then the subscriber can just retrieve the message value directly from the event object:
frm.Button1Click += (sender, e) => Lbl.Text = e.Message;
The important thing note in all of the above variations is that at no point does the class Form2 need to know anything about Form1. Having Form1 know about Form2 is unavoidable; after all, that's the object that will create a new Form2 instance and use it. But the relationship can be asymmetrical, with Form2 being usable by any object that needs the features it offers. By exposing the functionality as an event (and optionally with a property), it makes itself useful without limiting its usefulness to only the Form1 class.
The best in this case would be to have some OptionsService class/interface that is accessible via IServiceProvider.
Just add an event when something changes, and the rest of the app can respond to it.
There are lots of ways to perform communication between two Forms.
Some of them have already been explained to you. I am showing you the other way around.
Assuming you have to update some settings from the child form to the parent form. You can make use of these two ways as well :
Using System.Action (Here you simply pass the main forms function as the parameter to the child form like a callback function)
OpenForms Method ( You directly call one of your open forms)
Using System.Action
You can think of it as a callback function passed to the child form.
// -------- IN THE MAIN FORM --------
// CALLING THE CHILD FORM IN YOUR CODE LOOKS LIKE THIS
Options frmOptions = new Options(UpdateSettings);
frmOptions.Show();
// YOUR FUNCTION IN THE MAIN FORM TO BE EXECUTED
public void UpdateSettings(string data)
{
// DO YOUR STUFF HERE
}
// -------- IN THE CHILD FORM --------
Action<string> UpdateSettings = null;
// IN THE CHILD FORMS CONSTRUCTOR
public Options(Action<string> UpdateSettings)
{
InitializeComponent();
this.UpdateSettings = UpdateSettings;
}
private void btnUpdate_Click(object sender, EventArgs e)
{
// CALLING THE CALLBACK FUNCTION
if (UpdateSettings != null)
UpdateSettings("some data");
}
OpenForms Method
This method is easy (2 lines). But only works with forms that are open.
All you need to do is add these two lines where ever you want to pass some data.
Main frmMain = (Main)Application.OpenForms["Main"];
frmMain.UpdateSettings("Some data");
Properties is one option, shared static class - another option, events - another option...
You might try AutoMapper. Keep your options in a separate class and then use AutoMapper to shuttle the data between the class and the form.
Create a Class and put all your properties inside the class .. Create a Property in the parent class and set it from your child (options) form
You can have a function in Form B like so:
public SettingsResults GetNewSettings()
{
if(this.ShowDialog() == DialogResult.Ok)
{
return new SettingsResult { ... };
}
else
{
return null;
}
}
And you can call it like this:
...
using(var fb = new FormB())
{
var s = fb.GetNewSettings();
...
// Notify other parts of the application that settings have changed.
}
MVC, MVP, MVVM -- slight overkill for someone admittedly saying they want tutorials. Those are theories that have entire courses dedicated to them.
As already posted, passing an object around is probably easiest. If treating a class as an object (interchangeable in this sense) is new, then you may want to spend another 2-4 weeks figuring out properties and constructors and such.
I'm not a C# master by any means, but these concepts need to be pretty concrete if you want to go much further beyond passing values between two forms (also classes/objects in their own right). Not trying to be mean here at all, it just sounds like you're moving from something like VB6 (or any language with globals) to something far more structured.
Eventually, it will click.
This is probably sidestepping your problem a little bit, but my settings dialog uses the Application Settings construct. http://msdn.microsoft.com/en-us/library/k4s6c3a0.aspx
I can't find a good example that's similar to how I do it (which is actually having an actual class+object), but this covers another way of doing it:
Reading default application settings in C#
A form is a class, just like any other class. Add some public variables to your form class and set them when they click the button to close the form (technically they are just hiding it).
A VB.NET example, but you'll get the idea -
In your OptionsForm class:
Public Option1 as String = ""
etc. Set them when they hit the "Ok" button.
So in your main form, when they hit the "options" button - you create your options form:
OptionsForm.ShowDialog()
when it exits, you harvest your option settings from the public variables on the form:
option1 = OptionsForm.Option1
etc.
The best way to deal with communication between containers is to implement an observer class
The observer pattern is a software design pattern in which an object, called the subject, maintains a list of its dependents, called observers, and notifies them automatically of any state changes, usually by calling one of their methods.
(Wikipedia)
the way i do this is creating an Observer class, and inside it write something like this:
1 public delegate void dlFuncToBeImplemented(string signal);
2 public static event dlFuncToBeImplemented OnFuncToBeImplemented;
3 public static void FuncToBeImplemented(string signal)
4 {
5 OnFuncToBeImplemented(signal);
6 }
so basically: the first line says that there would be a function that somebody else will implement
the second line is creating an event that occurs when the delegated function will call
and the third line is the creation of the function that calls the event
so in your UserControl, you should add a function like this:
private void ObserverRegister()//will contain all observer function registration
{
Observer.OnFuncToBeImplemented += Observer_OnFuncToBeImplemented;
/*and more observer function registration............*/
}
void Observer_OnFuncToBeImplemented(string signal)//the function that will occur when FuncToBeImplemented(signal) will call
{
MessageBox.Show("Signal "+signal+" received!", "Atention!", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
}
and in your Form you should do something like:
public static int signal = 0;
public void button1_Click(object sender, EventArgs e)
{
Observer.FuncToBeImplemented(signal);//will call the event in the user control
}
and now, you can register this function to a whole bunch of other controls and containers and they will all get the signal
I hope this would help :)