I want to pass a value from Mainpage to Page2. When I click Button_Click the variable “t” is passed to Page2.
However I need to trigger the Button_Click event from code, but then a “NullReferenceException” is thrown.
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
Button_Click(new object(), new RoutedEventArgs());
}
public void Button_Click(object sender, RoutedEventArgs e)
{
string t = "Test";
navigate_page2(t);
}
public void navigate_page2(string t)
{
this.Frame.Navigate(typeof(Page2), t);
}
}
Button_Click(new object(), new RoutedEventArgs()); triggers the Button_Click event to do stuff, except when "navigate_page2" is called.
What is the difference between directly clicking and triggering the Button from code? I guess it is the "new RoutedEventArgs" somehow, but I don't know how to handle that... Thank you for any response!
Please do not call Button_Click directly, this method is associated with events in XAML.
If you want to re-use the code in the Button_Click event, you can pack it as a method to call.
Update
but then a “NullReferenceException” is thrown.
The problem is in this.Frame. for your current page, this.Frame does not exist. You need to create a sub-frame in xaml.
<Grid>
<Frame x:Name="MainFrame"/>
</Grid>
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
btn_handle();
}
public void Button_Click(object sender, RoutedEventArgs e)
{
btn_handle();
}
public void btn_handle()
{
string t = "Test";
navigate_page2(t);
}
public void navigate_page2(string t)
{
MainFrame.Navigate(typeof(Page2), t);
}
}
Best regards.
As I can understand you are trying to pass a value from one page to another let take example for two forms that you need to pass one value from a form to another with a trigger of any click of button.
Form2
public partial class Form2 : Form
{
public event EventHandler TextEvent;
public Form2()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
this.Hide();
if (TextEvent != null)
{
TextEvent(label1.Text, null);
}
}
}
Form1
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Form2 obj = new Form2();
obj.Show();
obj.TextEvent += obj_TextEvent;
}
void obj_TextEvent(object sender, EventArgs e)
{
label1.Text = sender.ToString();
}
}
Here what I am doing is I have made an event in Form2 which triggers at clicking Button1 of Form2 and the data is pass as a sender to Form1 where Form2 obj has initiated the event and set label1 of Form1 as label1.Text = sender.ToString();
Related
This is a demo example, I can't use the original code. This context is very simplified.
I want to call a button/event from the child form (form2) when I'm clicking a button from the mother form (form1). I want to do this via subscribing (which I don't really understard since I'm new to coding).
Mother form:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Form2 f = new Form2();
f.Show();
//Call the Button from Form2 here
}
}
Child Form:
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
MessageBox.Show("MessageBox called from Form1 or Form2");
}
}
What you want to do, the way you want to do it, is in general not a good idea as you should not be relying on UI controls on another from, from your other form.
What you can do to achieve what you asked for without rewriting anything is more like this:
1) in the button click of Form2, you do not do anything else than calling a method on Form2, event handler contains no other logic
2) you make that method of form2 public
3) from your button click on form1, you call that same public method of form2
again, this would work but it is not necessarily the best design, it really depends on the whole architecture of your app if this fits or not with the rest or there are better and different ways to accomplish this.
Don't call other form "button clicks", if you want to call some logic from different places, extract logic into dedicated class and call it from both places
public class MyLogic
{
public void Execute(string someParameter)
{
// Do something with parameter
}
}
Then use it in both forms
public partial class Form1 : Form
{
private readonly MyLogic _importantLogic;
public Form1()
{
InitializeComponent();
_importantLogic = new MyLogic();
}
private void button1_Click(object sender, EventArgs e)
{
_importantLogic.Execute(this.textBox1.Text);
}
}
public partial class Form2 : Form
{
private readonly MyLogic _importantLogic;
public Form2()
{
InitializeComponent();
_importantLogic = new MyLogic();
}
private void button1_Click(object sender, EventArgs e)
{
_importantLogic.Execute("Always Form 2");
}
}
I've created a new form, in which I have a toolbox. When I press a button in that form, it should relay that information that has been entered by the user(toolboxbox value) to the main form, in which it should say that piece of information in a label.
Since the method to create that username from the toolbox is private, I cannot access it from any other way. Making it public does not seem to make a difference, neither does get,set (from the way I've been trying to atleast).
Picture that may help explaining it:
Code (in which to create user):
namespace WindowsFormsApplication3
{
public partial class Newuserform : Form
{
public Newuserform()
{
InitializeComponent();
}
private void buttonCreateUser_Click(object sender, EventArgs e)
{
string uname = textboxUsername.ToString();
}
public void Unamecreate()
{
}
}
}
Form1 Code (To receive created user):
namespace WindowsFormsApplication3
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void exitToolStripMenuItem_Click(object sender, EventArgs e)
{
Application.Exit();
}
private void aboutToolStripMenuItem1_Click(object sender, EventArgs e)
{
Aboutform form2 = new Aboutform();
form2.Show();
}
private void newLocalUserToolStripMenuItem_Click(object sender, EventArgs e)
{
Newuserform formnewuser = new Newuserform();
formnewuser.Show();
}
}
}
you have a lot of options.
One way is to create an event and handle it in the main form.
public partial class Newuserform : Form
{
//the public property
public event EventHandler<string> UnameChanged;
public Newuserform()
{
InitializeComponent();
}
private void buttonCreateUser_Click(object sender, EventArgs e)
{
if (UnameChanged != null)
UnameChanged(textboxUsername.ToString()); //fire the event
}
}
Now, to "handle" the event, do the following in your main form:
private void newLocalUserToolStripMenuItem_Click(object sender, EventArgs e)
{
Newuserform formnewuser = new Newuserform();
formnewuser.UnameChanged += Handler;
formnewuser.Show();
}
private void Handler (object sender, string Uname)
{
// do something wit the new Uname.
}
note: recreating the Newuserform will require to cleanup previous attached resources.
I want to call a some combo-box items so i can make an if /else statements and output a form.The combo-box items are out side of my class(Form) how can i access them i tried this(below) but the error says does not exist in the current context.I also changed it
the method from private to public
public void buttonFinish_Click(object sender, EventArgs e)
{
if(comboBoxD.Text == "Alphabet" && comboBoxType.Text == "Numbers")
{
}
}
Send ComboBox from form1 to form2 using constructor. Here is example:
Form1 Class:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
Form2 f2 = new Form2(comboBox1, comboBox2);
f2.Show();
}
}
Form2 Class:
public partial class Form2 : Form
{
ComboBox comboBoxD;
ComboBox comboBoxType;
public Form2(ComboBox cb, ComboBox cbType)
{
InitializeComponent();
comboBoxD = cb;
comboBoxType = cbType;
}
private void Form2_Load(object sender, EventArgs e)
{
}
protected void buttonFinish_Click(object sender, EventArgs e)
{
if(comboBoxD.Text == "Alphabet" && comboBoxType.Text == "Numbers")
{
}
}
}
UPDATE:
Here is another approach for accessing controls present in another form.
Default Modifiers of every control is private. For controls you want to access from another form you have change Modifiers property as Public.
Form1 Class:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
Form2 f2 = new Form2(this);
f2.Show();
}
}
Form2 Class:
public partial class Form2 : Form
{
private Form1 f1;
public Form2(Form1 f)
{
InitializeComponent();
f1 = f;
}
protected void buttonFinish_Click(object sender, EventArgs e)
{
if(f1.comboBoxD.Text == "Alphabet" && f1.comboBoxType.Text == "Numbers")
{
}
}
}
This is because your ComboBox is only available in the codebehind file of your Form.
One solution would be to store a reference to your combobox as a property in your codebehind.
like this:
public ComboBox myCmbBox { get; private set; }
and access it in the codebehind of form2.
You can write a public method in your ComboBox's class and then call it from where you have instance of that form.
like this:
in your main form:
using (var modal = new MyModal())
{
modal.ShowDialog();
modal.getSomething();
}
in your modal:
public string getSomething()
{
return yourComboBox.Text;
}
Hello guys i am working on a Windows Form application in .Net C#.
Now i have a User control with a button inside it.
however i had to write the on-click handler in the main form rather than inside the user-control itself.
Now i want to know if there is anyway i can get the User-control object in the Button's on-click Handler. Since i had to make use of them few more times in the same form. I want to know which User-control's Button was click.
User Control
Button
Thank You :)
Here's an example of the UserControl raising a Custom Event that passes out the source UserControl that the Button was clicked on:
SomeUserControl:
public partial class SomeUserControl : UserControl
{
public event ButtonPressedDelegate ButtonPressed;
public delegate void ButtonPressedDelegate(SomeUserControl sender);
public SomeUserControl()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
if (ButtonPressed != null)
{
ButtonPressed(this); // pass the UserControl out as the parameter
}
}
}
Form1:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
someUserControl1.ButtonPressed += new SomeUserControl.ButtonPressedDelegate(SomeUserControl_ButtonPressed);
someUserControl2.ButtonPressed += new SomeUserControl.ButtonPressedDelegate(SomeUserControl_ButtonPressed);
someUserControl3.ButtonPressed += new SomeUserControl.ButtonPressedDelegate(SomeUserControl_ButtonPressed);
}
void SomeUserControl_ButtonPressed(SomeUserControl sender)
{
// do something with "sender":
sender.BackColor = Color.Red;
}
}
You can use event:
public delegate void ButtonClicked();
public ButtonClicked OnButtonClicked;
You can then subscribe the event anywhere, for instance, in your MainForm, you have a user control called demo;
demo.OnButtonClicked +=()
{
// put your actions here.
}
Just walk the .Parent() chain until you find a Control that is the same Type as your UserControl. In the example below, the UserControl is of Type SomeUserControl:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
someUserControl1.button1.Click += new EventHandler(button1_Click);
someUserControl2.button1.Click += new EventHandler(button1_Click);
someUserControl3.button1.Click += new EventHandler(button1_Click);
}
void button1_Click(object sender, EventArgs e)
{
Button btn = (Button)sender;
Control uc = btn.Parent;
while (uc != null && !(uc is SomeUserControl))
{
uc = uc.Parent;
}
uc.BackColor = Color.Red;
MessageBox.Show(uc.Name);
}
}
Basically; Form1 has 2 buttons, Form2 has 1 button.
When you click Form2's button it checks which button on Form1 you clicked, opening Form3 or Form4 depending on which button you clicked (on Form1).
So I've utilized Mark Halls first method of passing variables between forms. Now for the second half of my closed refinement.
Form1
private void btnLogin_Click(object sender, EventArgs e)
{
// Call function while storing variable info.
Account("login");
}
private void btnRegister_Click(object sender, EventArgs e)
{
// Call function while storing variable info.
Account("register");
}
// Function used to pass Variable info to Account form while opening it as instance.
private void Account(string formtype)
{
// Generate/Name new instant of form.
frontend_account frmAcc = new frontend_account();
// Pass variable to instance.
frmAcc.CheckButtonClick = formtype;
// Show form instance.
frmAcc.Show(this);
// Hide this instance.
this.Hide();
}
Form2
// String Variable to store value from Login.
public string CheckButtonClick { get; set; }
private void btnContinue_Click(object sender, EventArgs e)
{
// If statement to open either Main form or Registration form, based on Login variable.
if (CheckButtonClick == "login")
{
// Generate/Name new instant of form.
frontend_main frmMain = new frontend_main();
// Show form instant.
frmMain.Show();
// Close this instant.
this.Close();
}
else if (CheckButtonClick == "register")
{
// Generate/Name new instant of form.
frontend_register frmReg = new frontend_register();
// Show form instant.
frmReg.Show();
// Close this instant.
this.Close();
}
}
On Form2 there are TWO radio buttons, can I adept that code to set the focus of a tab control when a form is opened? ie. if radClient is checked set focus on tabcontrol after opening winform, else if radStudent is checked set focus on tabcontrol (other page) after opening winform... and i guess don't open a winform if no radio is checked.
I believe this will set the focus;
// Sets focus to first tab.
tabRegister.SelectedTab = tabRegister.TabPages[0];
// Sets focus to second tab.
tabRegister.SelectedTab = tabRegister.TabPages[1];
In your example the first problem I see is you are closing your parent form which closes your Form1 and disposes of Your Form2, What I would do is Hide Form1 instead of Closing it, I would then create a public property on Form2 to pass in the Button that was selected. But anytime you are opening and closing multiple Forms it can get messy, what I would do would be to create UserControls for your additional Forms and swap them out in a Panel. The first example is how to do it the way that you asked.
Form
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void btnLogin_Click(object sender, EventArgs e)
{
ShowForm2("login");
}
private void btnRegister_Click(object sender, EventArgs e)
{
ShowForm2("register");
}
private void ShowForm2(string formtype)
{
Form2 f2 = new Form2(); // Instantiate a Form2 object.
f2.CheckButtonClick = formtype;
f2.Show(this); // Show Form2 and
this.Hide(); // closes the Form1 instance.
}
}
Form2
ublic partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
public string CheckButtonClick { get; set; }
private void button1_Click(object sender, EventArgs e)
{
if (CheckButtonClick == "login")
{
Form3 f3 = new Form3(); // Instantiate a Form3 object.
f3.Show(); // Show Form3 and
this.Close(); // closes the Form2 instance.
}
else if (CheckButtonClick == "register")
{
Form4 f4 = new Form4(); // Instantiate a Form4 object.
f4.Show(); // Show Form4 and
this.Close(); // closes the Form2 instance.
}
}
}
Form3 and Form4 note since Form1 is long forgotten to these forms I search for it to Open back up
public partial class Form3 : Form
{
public Form3()
{
InitializeComponent();
}
private void Form3_FormClosed(object sender, FormClosedEventArgs e)
{
FormCollection frms = Application.OpenForms;
foreach (Form f in frms)
{
if (f.Name == "Form1")
{
f.Show();
break;
}
}
}
}
The second Option with UserControls has one Form with a Panel on it. It uses events to signal the Form to Change Controls plus a public property on UserControl2
public partial class Form1 : Form
{
string logonType;
public Form1()
{
InitializeComponent();
}
private void userControl1_LoginOrRegisterEvent(object sender, LoginOrRegisterArgs e)
{
logonType = e.Value;
userControl2.BringToFront();
}
private void userControl2_ControlFinshedEvent(object sender, EventArgs e)
{
if (logonType == "logon")
userControl3.BringToFront();
else if (logonType == "register")
userControl4.BringToFront();
}
private void userControl3_ControlFinshedEvent(object sender, EventArgs e)
{
userControl1.BringToFront();
}
private void userControl4_ControlFinshedEvent(object sender, EventArgs e)
{
userControl1.BringToFront();
}
}
UserControl1
public partial class UserControl1 : UserControl
{
public delegate void LoginOrRegisterHandler(object sender, LoginOrRegisterArgs e);
public event LoginOrRegisterHandler LoginOrRegisterEvent;
public UserControl1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
LoginOrRegisterArgs ea = new LoginOrRegisterArgs("logon");
LoginOrRegisterEvent(sender, ea);
}
private void button2_Click(object sender, EventArgs e)
{
LoginOrRegisterArgs ea = new LoginOrRegisterArgs("register");
LoginOrRegisterEvent(sender, ea);
}
}
public class LoginOrRegisterArgs
{
public LoginOrRegisterArgs(string s) {Value = s;}
public string Value {get; private set;}
}
UserControl2
public partial class UserControl2 : UserControl
{
public delegate void ControlFinishedHandler(object sender, EventArgs e);
public event ControlFinishedHandler ControlFinshedEvent;
public UserControl2()
{
InitializeComponent();
}
public string SetLogonType { get; set; }
private void button1_Click(object sender, EventArgs e)
{
ControlFinshedEvent(sender, new EventArgs());
}
}
UserControl3 & UserControl4 exactly the same except for different Class Name
public partial class UserControl3 : UserControl
{
public delegate void ControlFinishedHandler(object sender, EventArgs e);
public event ControlFinishedHandler ControlFinshedEvent;
public UserControl3()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
ControlFinshedEvent(sender, new EventArgs());
}
}
As I suggested in my comment, one of the best way I know to pass data between forms is to use events.
Basically, in the "child" forms, you declare an event that will be handled, or listened to, by the "main" form.
See the referenced answer from my comment, and if you have specific questions on how to adapt it, ask away.
Cheers