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 was wondering how you would close the Form that is currently in focus or the one which a control is contained in. For example, I have an imported header with a menu that I import into all forms in my application.
This is the (simplified) code in my Header class:
public static Panel GetHeader()
{
...
menuItem.Text = "Menu Item";
menuItem.Name = "Next form to open";
menuItem.Click += toolStrip_Click;
...
}
public static void toolStrip_Click(object sender, EventArgs e)
{
ToolStripMenuItem menuItem = sender as ToolStripMenuItem;
NavigationClass.SaveNextForm(menuItem.Name);
}
The navigation class is just something I made which will select the next form to open but I couldn't find anything to then close the current one (since Close() isn't an option due to it being imported with Controls.Add(HeaderClass.GetHeader))
Edit
Just to make clear, this form is in another file which is just a normal class file. That's where the difficulty lies because I'm trying to avoid a severe violation of the DRY principle
Don't use static handlers as #Hans Passant suggests. That is important.
Try sending your main form to your class as a parameter, and store it in that class. This can be done either when you are instantiating your class, or after that. Then, when you need to close the form, call it's Close method. Since you don't include your codes in more details, here is my example with some assumptions.
public class MainForm : Form
{
private HeaderClass HeaderClass;
public MainForm()
{
HeaderClass = new HeaderClass(this);
}
}
public class HeaderClass
{
private MainForm MainForm;
public HeaderClass(MainForm mainForm)
{
MainForm = mainForm;
}
public void MethodThatYouNeedToCloseTheFormFrom()
{
...
MainForm.Close();
...
}
}
Let us know if you require any more elaboration.
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 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 :)