Winfrom controls data transfer between forms

Method 1
You can customize a constructor in a subform. The parameter type is the main form. When you want to display the subform, use this constructor to instantiate the subform and pass this pointer in. The Code is as follows:
Main form. cs
Public class frmMain: Form
{
...
FrmControl controlForm = new frmControl (this );
ControlForm. Show ();
}
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Subform. cs
Subform. cs
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--> Public class frmControl: Form // subform, used to control some display of the main Form!
{
Private frmMain mainForm;
Public frmControl (frmMain mainForm)
{
This. mainForm = mainForm;
}
Private void button#click (object sender, EventArgs e)
{
FrmMain. textBox1.Text = this. textBox1.Text;
// Pass the text box value of the subform to the text box of the main form!
}
}
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Method 2
In fact, the method is not very good. Although the implementation is very simple, just want to change the title Text of the form, it will pass the reference of the entire main form to the subform, this method is not very elegant, we use interfaces to improve the above method, which can limit the function exposed to subforms and reduce the coupling between forms. The Code is as follows:
Define the API. cs
Public interface IChangeTitle:
{
Void ChangeTitle (string title );
}
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Main form. cs
Main form. cs
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--> Public class frmMain: Form, IChangeTitle
{
...
FrmControl controlForm = new frmControl (this );
ControlForm. Show ();
Public void ChangeTitle (string title)
{
This. Text = title;
}
}
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Subform. cs
Subform. cs
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--> Public class frmControl: Form // subform, used to control some display of the main Form!
{
Private IChangeTitle ichangeTitle;
Public frmControl (IChangeTitle ichangeTitle)
{
This. ichangeTitle = ichangeTitle;
}
Private void button#click (object sender, EventArgs e)
{
// Call a method through an interface
IchangeTitle. ChangeTitle (this. textBox1.Text );
}
}
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Method 3
To further reduce the coupling between forms, we can use delegation to achieve this requirement. The Code is as follows:
Main form. cs
Main form. cs
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--> // Assign a value to the delegate variable to the main form:
Public partial class MainForm: Form
{
Private ChildForm loginForm = new ChildForm ();
Public MainForm ()
{
InitializeComponent ();
LoginForm. TitleChanged = new
ChildForm. TitleChangedEventHandler (FormTitleChanged );
}

Protected void FormTitleChanged (string title)
{
This. Text = title;
}

Private void button#click (object sender, EventArgs e)
{
LoginForm. Show ();
}
}
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Subform. cs
Subform. cs
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--> Public partial class ChildForm: Form
{
// Declare and define Delegation
Public delegate void TitleChangedHandler (string title );
Public TitleChangedEventHandler TitleChanged;

Public ChildForm ()
{
InitializeComponent ();
}
Private void btn_ OK _Click (object sender, EventArgs e)
{
If (TitleChanged! = Null)
TitleChanged ("Test Title"); // delegate call

}
}
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Method 4
You can also define a custom event in the subform, and then customize an event parameter to pass some information you want to pass. The Code is as follows:
Main form. cs
Main form. cs
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--> // Subscribe to this event on the main form.
Public partial class MainForm: Form
{
Private ChildForm loginForm = new ChildForm ();
Public MainForm ()
{
InitializeComponent ();
LoginForm. TitleChanged + =
New ChildForm. TitleChangedEventHandler (FormTitleChanged );
}

Protected void FormTitleChanged (object sender, ChildForm. TitleChangedEventArgs e)
{
This. Text = e. Title;
}

Private void button#click (object sender, EventArgs e)
{
LoginForm. Show ();
}
}
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Subform. cs
Subform. cs
<! --

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--> Public partial class ChildForm: Form
{
Public class TitleChangedEventArgs: EventArgs // event parameter class
{
Private string title = "";
Public string Title
{
Get {return title ;}
Set {title = value ;}
}
}
// Declare the delegate
Public delegate void TitleChangedEventHandler (object sender, TitleChangedEventArgs e );
// Define the event
Public event TitleChangedEventHandler TitleChanged;

Public ChildForm ()
{
InitializeComponent ();
}

Private void btn_ OK _Click (object sender, EventArgs e)
{
TitleChangedEventArgs e1 = new TitleChangedEventArgs ();
E1.Title = "Login sucessed ";
OnTitleChanged (e1); // trigger event

}
// Method for triggering an event
Protected virtual void OnTitleChanged (TitleChangedEventArgs e)
{
If (TitleChanged! = Null)
TitleChanged (this, e );
}
}

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