I'm pretty new to C# - but it all went quite well - to this point.
I start with a form and a class which does most of the work (non static and in the program part). I instantiate an object of the class in form 1 and do a log in.
Then I switch over to the next form, form2. Actually, the the class does that. I have a method there, that contains the line:
this.f2 = new Form2();
and then:
f2.Show();
f2 is a class member of the type Form2 - and all just works fine - up to this point.
This Form2 just consists of a big text box in which I want to display network events. The event handler works just fine - but the reference to the form just doesn't seem to work. If I do
f2.tetBox1.Text = "Some text";
it just won't change the the text in the text box.
What am I doing wrong here?
Here is a more detailed description of what I'm doing:
Form1 passes some log in information to myProg, being an instance of MyClass. If the login was successful, Form1 calls myProg.makeForm();
This is what the method in MyClass looks like:
public void makeForm() {
this.f2 = new Form2();
f2.Show();
this.sendString("start f2");
}
This is MyClass.sendString():
private void sendString(string text) {
SystemSounds.Beep.Play();
this.f2.setTextBox(text);
}
This calls, as you see, setTextBox() of Form2 - which I implemented as proposed here. The strange thing is, that up to this point all works well. The Form2 gets shown an textBox1 contains "start f2" - as expected. But when an event comes in, the text in textBox1 doesn't change. the beep get played all right - so the method sendString() gets called alright.
One thing I have observed: If the beep line is placed after the call to this.f2.setTextBox(text);, it doesn't get played if the method is called from the event handler.
f2, btw., is a private member of MyClass:
private Form2 f2;
Any control created by the designer (e.g. dropped from the Toolbox at design-time) is automatically set as private. Therefore, you can't access it from another form.
You don't want to start messing with the designer, instead - create a property on your Form2 which will allow you to modify the text of the Textbox from Form1.
A short example is something like this:
Form2:
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
// When modifying the Text property it will change the text in textbox1
public string Text
{
get { return textBox1.Text; }
set { textBox1.Text = value; }
}
}
Then, in Form1:
Form2 frm2 = new Form2();
frm2.Text = "123"; // Uses the public Text property declared in Form2
frm2.Show();
By default a textbox is private when you place it via the designer, which means you can't access textBox1 from outside of Form2 (it's only 'visible' to code within the Form2 class). You could change the textbox to be internal or public (which would let you do the following (from Form1):
f2.tetBox1.Text = "Some text";
BUT that would be exposing parts of Form2 which only Form2 should really know about...so it isn't the cleanest solution (though it would be likely the quickest))
A better solution might be to create a method or property (internal or public) in Form2 which will set the text value. E.g.:
internal void SetText(string value)
{
textBox1.Text = value;
}
As the method (or property) resides in Form2, it has access to the text box, so it can set the value while textBox1 is still private.
It's safer exposing this method to 'external' code (as opposed to making the textbox visible to them) as all they can do is change the text - whereas exposing the whole textbox might let callers try to change background colour, etc.
Related
I would like to set comboBox.SelectedValue when I select the row in my dataGridView on first form to populate comboBox with that value on another form,
On second form in my load event I have comboBox.DataSource, DisplayMember, ValueMember set it correctly but nothing is happening when I set selectedValue on first. Everything works great when I do it on one form
Form in Windows Forms is a class like other C# classes. The way of communicating between forms are the same as classes. You can consider this options when communicating between classes:
Manipulate second Form from first Form
You can add suitable parameters to the constructor of the second form. Then you can pass values to the constructor when creating an instance of the second form. In the second form store parameters in member fields and use them when you nees.
You can create public property or method in the second form and set those properties after creating an instance of the second form. This way you can use them when you need in the second form. This option is not limited to passing values when creating the second form. You can even use that property during the execution of second Form. Also it's useful for getting a value from it.
As another option you can make the control which you want to manipulate it public and this way you can access to it from other form. Using a method is a more recommended way of doing this.
Manipulate first Form from second form
You can create a public method or property in first form and pass an instance of the first form to second form. Then using that method/property on the passed instance, you can manipulate the first form.
You can create an event in second form and after creating an instance of second form subscribe for it in first form and put the code for changing the form in the handler. Then it's enough to raise the event in second form.
You can define a public property of type Action or some other delegate type in second form and then after creating an instance of second form, assign the property using a custom action. Then in second form, it's enough to invoke the action when you need to manipulate first form.
Also here you can make a control of first form to be public and then if you pass an instance of the first form to the second form, you can manipulate the control. It's recommended to use other solutions. It's like creating public property or method, but a method which performs specific task on the control is better that exposing the whole control. But you may need this solution some times.
Here are some useful examples about above solutions.
Manipulate second Form from first Form
Example1 - Using constructor of second Form
Use this example when you need to pass some data to second form, when creating the second form.
public partial class Form2 : Form
{
int selectedValue;
public Form2(int value)
{
InitializeComponent();
selectedValue = value;
}
private void Form2_Load(object sender, EventArgs e)
{
//Load data
this.comboBox1.DataSource = new MyDbContext().Categories.ToList();
this.comboBox1.DisplayMember = "Name";
this.comboBox1.ValueMember = "Id";
this.comboBox1.SelectedValue = selectedValue;
}
}
Then in your first form, it's enough to pass the value to Form2 when you create a new instance of it:
var value = 2; // Or get it from grid
var f = new Form2(value);
f.ShowDialog();
Example2 - using public Property or Method of second Form
Use this example when you need to pass some data to second form, when creating or even after creation of second form.
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
public string SomeValue
{
get { return textBox1.Text;}
set { textBox1.Text = value;}
}
}
Then in your first form, it's enough to pass the value to Form2 when you need, after creating Form2 or whenever you need to set value of textBox1 on Form2:
var f = new Form2(); //value is not needed here
f.SomeValue = "some value";
f.Show();
//...
f.SomeValue = "some other value";
Example 3 - Making a Control of Second form public
Use this example when you need to change a property of a control on second form, when creating or even after creation of second form. It's better to use public property or method instead of exposing whole control properties.
In your Form, at designer, select the control and in Properties window set the Modifiers property to Public. Also make sure the GenerateMember property is true. Then you can simply access this control using its name from outside of the Form.
var f = new Form2();
f.textBox1= "some value";
Manipulate first Form from second form
Example 4 - Create public Method or Property in first Form and pass an instance of First Form to constructor of second Form
Use this example when you need to change first Form from second Form.
In your Form1, create a property of a method that accepts some parameters and put the logic in it:
public void ChangeTextBox1Text(string text)
{
this.textBox1.Text = text;
}
Then create a constructor in Form2 which accepts a parameter of type Form1 and keep the passed value in a member field and use it when you need:
Form1 form1;
public Form2 (Form1 f)
{
InitializeComponent();
form1 = f;
}
private void button1_Click(object sender, EventArgs e)
{
form1.ChangeTextBox1Text("Some Value");
}
Now when creating Form2 you should pass an instance of Form1 to it:
var f = new Form2(this);
f.Show();
Example 5 - Using event of second Form in first Form
Take a look at this post. It's about communication between form and a control, but it's applicable to communication between forms also.
Example 6 - Injection an Action in second Form
Take a look at this post. It's about communication between form and a control, but it's applicable to communication between forms also.
Example 7 - Making a Control of first form public
In this solution you need to make a control in first form public, like example 3. Then like example 4 pass an instance of the first form to second form and keep it in a field and use it when you need. Using a public method or property is preferred.
Form1 form1;
public Form2 (Form1 f)
{
InitializeComponent();
form1 = f;
}
private void button1_Click(object sender, EventArgs e)
{
form1.textBox1.Text = "Some Value";
}
when creating Form2 you should pass an instance of Form1 to it:
var f = new Form2(this);
f.Show();
I would like to set comboBox.SelectedValue when I select the row in my dataGridView on first form to populate comboBox with that value on another form,
On second form in my load event I have comboBox.DataSource, DisplayMember, ValueMember set it correctly but nothing is happening when I set selectedValue on first. Everything works great when I do it on one form
Form in Windows Forms is a class like other C# classes. The way of communicating between forms are the same as classes. You can consider this options when communicating between classes:
Manipulate second Form from first Form
You can add suitable parameters to the constructor of the second form. Then you can pass values to the constructor when creating an instance of the second form. In the second form store parameters in member fields and use them when you nees.
You can create public property or method in the second form and set those properties after creating an instance of the second form. This way you can use them when you need in the second form. This option is not limited to passing values when creating the second form. You can even use that property during the execution of second Form. Also it's useful for getting a value from it.
As another option you can make the control which you want to manipulate it public and this way you can access to it from other form. Using a method is a more recommended way of doing this.
Manipulate first Form from second form
You can create a public method or property in first form and pass an instance of the first form to second form. Then using that method/property on the passed instance, you can manipulate the first form.
You can create an event in second form and after creating an instance of second form subscribe for it in first form and put the code for changing the form in the handler. Then it's enough to raise the event in second form.
You can define a public property of type Action or some other delegate type in second form and then after creating an instance of second form, assign the property using a custom action. Then in second form, it's enough to invoke the action when you need to manipulate first form.
Also here you can make a control of first form to be public and then if you pass an instance of the first form to the second form, you can manipulate the control. It's recommended to use other solutions. It's like creating public property or method, but a method which performs specific task on the control is better that exposing the whole control. But you may need this solution some times.
Here are some useful examples about above solutions.
Manipulate second Form from first Form
Example1 - Using constructor of second Form
Use this example when you need to pass some data to second form, when creating the second form.
public partial class Form2 : Form
{
int selectedValue;
public Form2(int value)
{
InitializeComponent();
selectedValue = value;
}
private void Form2_Load(object sender, EventArgs e)
{
//Load data
this.comboBox1.DataSource = new MyDbContext().Categories.ToList();
this.comboBox1.DisplayMember = "Name";
this.comboBox1.ValueMember = "Id";
this.comboBox1.SelectedValue = selectedValue;
}
}
Then in your first form, it's enough to pass the value to Form2 when you create a new instance of it:
var value = 2; // Or get it from grid
var f = new Form2(value);
f.ShowDialog();
Example2 - using public Property or Method of second Form
Use this example when you need to pass some data to second form, when creating or even after creation of second form.
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
public string SomeValue
{
get { return textBox1.Text;}
set { textBox1.Text = value;}
}
}
Then in your first form, it's enough to pass the value to Form2 when you need, after creating Form2 or whenever you need to set value of textBox1 on Form2:
var f = new Form2(); //value is not needed here
f.SomeValue = "some value";
f.Show();
//...
f.SomeValue = "some other value";
Example 3 - Making a Control of Second form public
Use this example when you need to change a property of a control on second form, when creating or even after creation of second form. It's better to use public property or method instead of exposing whole control properties.
In your Form, at designer, select the control and in Properties window set the Modifiers property to Public. Also make sure the GenerateMember property is true. Then you can simply access this control using its name from outside of the Form.
var f = new Form2();
f.textBox1= "some value";
Manipulate first Form from second form
Example 4 - Create public Method or Property in first Form and pass an instance of First Form to constructor of second Form
Use this example when you need to change first Form from second Form.
In your Form1, create a property of a method that accepts some parameters and put the logic in it:
public void ChangeTextBox1Text(string text)
{
this.textBox1.Text = text;
}
Then create a constructor in Form2 which accepts a parameter of type Form1 and keep the passed value in a member field and use it when you need:
Form1 form1;
public Form2 (Form1 f)
{
InitializeComponent();
form1 = f;
}
private void button1_Click(object sender, EventArgs e)
{
form1.ChangeTextBox1Text("Some Value");
}
Now when creating Form2 you should pass an instance of Form1 to it:
var f = new Form2(this);
f.Show();
Example 5 - Using event of second Form in first Form
Take a look at this post. It's about communication between form and a control, but it's applicable to communication between forms also.
Example 6 - Injection an Action in second Form
Take a look at this post. It's about communication between form and a control, but it's applicable to communication between forms also.
Example 7 - Making a Control of first form public
In this solution you need to make a control in first form public, like example 3. Then like example 4 pass an instance of the first form to second form and keep it in a field and use it when you need. Using a public method or property is preferred.
Form1 form1;
public Form2 (Form1 f)
{
InitializeComponent();
form1 = f;
}
private void button1_Click(object sender, EventArgs e)
{
form1.textBox1.Text = "Some Value";
}
when creating Form2 you should pass an instance of Form1 to it:
var f = new Form2(this);
f.Show();
I would like to set comboBox.SelectedValue when I select the row in my dataGridView on first form to populate comboBox with that value on another form,
On second form in my load event I have comboBox.DataSource, DisplayMember, ValueMember set it correctly but nothing is happening when I set selectedValue on first. Everything works great when I do it on one form
Form in Windows Forms is a class like other C# classes. The way of communicating between forms are the same as classes. You can consider this options when communicating between classes:
Manipulate second Form from first Form
You can add suitable parameters to the constructor of the second form. Then you can pass values to the constructor when creating an instance of the second form. In the second form store parameters in member fields and use them when you nees.
You can create public property or method in the second form and set those properties after creating an instance of the second form. This way you can use them when you need in the second form. This option is not limited to passing values when creating the second form. You can even use that property during the execution of second Form. Also it's useful for getting a value from it.
As another option you can make the control which you want to manipulate it public and this way you can access to it from other form. Using a method is a more recommended way of doing this.
Manipulate first Form from second form
You can create a public method or property in first form and pass an instance of the first form to second form. Then using that method/property on the passed instance, you can manipulate the first form.
You can create an event in second form and after creating an instance of second form subscribe for it in first form and put the code for changing the form in the handler. Then it's enough to raise the event in second form.
You can define a public property of type Action or some other delegate type in second form and then after creating an instance of second form, assign the property using a custom action. Then in second form, it's enough to invoke the action when you need to manipulate first form.
Also here you can make a control of first form to be public and then if you pass an instance of the first form to the second form, you can manipulate the control. It's recommended to use other solutions. It's like creating public property or method, but a method which performs specific task on the control is better that exposing the whole control. But you may need this solution some times.
Here are some useful examples about above solutions.
Manipulate second Form from first Form
Example1 - Using constructor of second Form
Use this example when you need to pass some data to second form, when creating the second form.
public partial class Form2 : Form
{
int selectedValue;
public Form2(int value)
{
InitializeComponent();
selectedValue = value;
}
private void Form2_Load(object sender, EventArgs e)
{
//Load data
this.comboBox1.DataSource = new MyDbContext().Categories.ToList();
this.comboBox1.DisplayMember = "Name";
this.comboBox1.ValueMember = "Id";
this.comboBox1.SelectedValue = selectedValue;
}
}
Then in your first form, it's enough to pass the value to Form2 when you create a new instance of it:
var value = 2; // Or get it from grid
var f = new Form2(value);
f.ShowDialog();
Example2 - using public Property or Method of second Form
Use this example when you need to pass some data to second form, when creating or even after creation of second form.
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
public string SomeValue
{
get { return textBox1.Text;}
set { textBox1.Text = value;}
}
}
Then in your first form, it's enough to pass the value to Form2 when you need, after creating Form2 or whenever you need to set value of textBox1 on Form2:
var f = new Form2(); //value is not needed here
f.SomeValue = "some value";
f.Show();
//...
f.SomeValue = "some other value";
Example 3 - Making a Control of Second form public
Use this example when you need to change a property of a control on second form, when creating or even after creation of second form. It's better to use public property or method instead of exposing whole control properties.
In your Form, at designer, select the control and in Properties window set the Modifiers property to Public. Also make sure the GenerateMember property is true. Then you can simply access this control using its name from outside of the Form.
var f = new Form2();
f.textBox1= "some value";
Manipulate first Form from second form
Example 4 - Create public Method or Property in first Form and pass an instance of First Form to constructor of second Form
Use this example when you need to change first Form from second Form.
In your Form1, create a property of a method that accepts some parameters and put the logic in it:
public void ChangeTextBox1Text(string text)
{
this.textBox1.Text = text;
}
Then create a constructor in Form2 which accepts a parameter of type Form1 and keep the passed value in a member field and use it when you need:
Form1 form1;
public Form2 (Form1 f)
{
InitializeComponent();
form1 = f;
}
private void button1_Click(object sender, EventArgs e)
{
form1.ChangeTextBox1Text("Some Value");
}
Now when creating Form2 you should pass an instance of Form1 to it:
var f = new Form2(this);
f.Show();
Example 5 - Using event of second Form in first Form
Take a look at this post. It's about communication between form and a control, but it's applicable to communication between forms also.
Example 6 - Injection an Action in second Form
Take a look at this post. It's about communication between form and a control, but it's applicable to communication between forms also.
Example 7 - Making a Control of first form public
In this solution you need to make a control in first form public, like example 3. Then like example 4 pass an instance of the first form to second form and keep it in a field and use it when you need. Using a public method or property is preferred.
Form1 form1;
public Form2 (Form1 f)
{
InitializeComponent();
form1 = f;
}
private void button1_Click(object sender, EventArgs e)
{
form1.textBox1.Text = "Some Value";
}
when creating Form2 you should pass an instance of Form1 to it:
var f = new Form2(this);
f.Show();
I would like to set comboBox.SelectedValue when I select the row in my dataGridView on first form to populate comboBox with that value on another form,
On second form in my load event I have comboBox.DataSource, DisplayMember, ValueMember set it correctly but nothing is happening when I set selectedValue on first. Everything works great when I do it on one form
Form in Windows Forms is a class like other C# classes. The way of communicating between forms are the same as classes. You can consider this options when communicating between classes:
Manipulate second Form from first Form
You can add suitable parameters to the constructor of the second form. Then you can pass values to the constructor when creating an instance of the second form. In the second form store parameters in member fields and use them when you nees.
You can create public property or method in the second form and set those properties after creating an instance of the second form. This way you can use them when you need in the second form. This option is not limited to passing values when creating the second form. You can even use that property during the execution of second Form. Also it's useful for getting a value from it.
As another option you can make the control which you want to manipulate it public and this way you can access to it from other form. Using a method is a more recommended way of doing this.
Manipulate first Form from second form
You can create a public method or property in first form and pass an instance of the first form to second form. Then using that method/property on the passed instance, you can manipulate the first form.
You can create an event in second form and after creating an instance of second form subscribe for it in first form and put the code for changing the form in the handler. Then it's enough to raise the event in second form.
You can define a public property of type Action or some other delegate type in second form and then after creating an instance of second form, assign the property using a custom action. Then in second form, it's enough to invoke the action when you need to manipulate first form.
Also here you can make a control of first form to be public and then if you pass an instance of the first form to the second form, you can manipulate the control. It's recommended to use other solutions. It's like creating public property or method, but a method which performs specific task on the control is better that exposing the whole control. But you may need this solution some times.
Here are some useful examples about above solutions.
Manipulate second Form from first Form
Example1 - Using constructor of second Form
Use this example when you need to pass some data to second form, when creating the second form.
public partial class Form2 : Form
{
int selectedValue;
public Form2(int value)
{
InitializeComponent();
selectedValue = value;
}
private void Form2_Load(object sender, EventArgs e)
{
//Load data
this.comboBox1.DataSource = new MyDbContext().Categories.ToList();
this.comboBox1.DisplayMember = "Name";
this.comboBox1.ValueMember = "Id";
this.comboBox1.SelectedValue = selectedValue;
}
}
Then in your first form, it's enough to pass the value to Form2 when you create a new instance of it:
var value = 2; // Or get it from grid
var f = new Form2(value);
f.ShowDialog();
Example2 - using public Property or Method of second Form
Use this example when you need to pass some data to second form, when creating or even after creation of second form.
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}
public string SomeValue
{
get { return textBox1.Text;}
set { textBox1.Text = value;}
}
}
Then in your first form, it's enough to pass the value to Form2 when you need, after creating Form2 or whenever you need to set value of textBox1 on Form2:
var f = new Form2(); //value is not needed here
f.SomeValue = "some value";
f.Show();
//...
f.SomeValue = "some other value";
Example 3 - Making a Control of Second form public
Use this example when you need to change a property of a control on second form, when creating or even after creation of second form. It's better to use public property or method instead of exposing whole control properties.
In your Form, at designer, select the control and in Properties window set the Modifiers property to Public. Also make sure the GenerateMember property is true. Then you can simply access this control using its name from outside of the Form.
var f = new Form2();
f.textBox1= "some value";
Manipulate first Form from second form
Example 4 - Create public Method or Property in first Form and pass an instance of First Form to constructor of second Form
Use this example when you need to change first Form from second Form.
In your Form1, create a property of a method that accepts some parameters and put the logic in it:
public void ChangeTextBox1Text(string text)
{
this.textBox1.Text = text;
}
Then create a constructor in Form2 which accepts a parameter of type Form1 and keep the passed value in a member field and use it when you need:
Form1 form1;
public Form2 (Form1 f)
{
InitializeComponent();
form1 = f;
}
private void button1_Click(object sender, EventArgs e)
{
form1.ChangeTextBox1Text("Some Value");
}
Now when creating Form2 you should pass an instance of Form1 to it:
var f = new Form2(this);
f.Show();
Example 5 - Using event of second Form in first Form
Take a look at this post. It's about communication between form and a control, but it's applicable to communication between forms also.
Example 6 - Injection an Action in second Form
Take a look at this post. It's about communication between form and a control, but it's applicable to communication between forms also.
Example 7 - Making a Control of first form public
In this solution you need to make a control in first form public, like example 3. Then like example 4 pass an instance of the first form to second form and keep it in a field and use it when you need. Using a public method or property is preferred.
Form1 form1;
public Form2 (Form1 f)
{
InitializeComponent();
form1 = f;
}
private void button1_Click(object sender, EventArgs e)
{
form1.textBox1.Text = "Some Value";
}
when creating Form2 you should pass an instance of Form1 to it:
var f = new Form2(this);
f.Show();
Situation i have: textbox(to input your name) on form1. From that form1 on button click i go to form2. From form2 button click to form3. On form3 on button click i need to writte me in empty textbox value from textbox on form1 that user wrote down.
example: on form1 in textbox1 i write my name "Djuzla". When i go to form3 and click button to see what name i wrote in form1 it should show in empty textbox3 form3 "Djuzla".
I'm stuck with this few hours now, and it stupid problem but i have no idea what to do next.. tried all from zillion theards on net :p
You could modify the constructor of the form to take one more argument to hold the value of the textBox.
Store the value in a property. If you are developing for asp.net, use session or ViewState. Did I understand your question?
You may access the PreviousPage property from the page, or set a session variable (or a cookie) and then retrieve it on page load etc. but the most straightforward solution is to use the PreviousPage property on the page to access the data from previous page.
I've answered similarly... Since you are going from Form 1 to 2 to 3, you could basically take the same approach in this solution to cascade the value out and back as needed, not just one way...
My Other Solution to similar question...
The solutions that pass a value around can get quite sloppy because there's no guarantee that the value inside the textbox won't change after you've already passed it somewhere. Instead, it's more sensible to pass a function around which resolves the value from the TextBox when called, which will result in always getting the lastest value.
void button1_Click() {
form2 = new Form2(() => textBoxName.Text);
}
class Form2 : Form {
...
public Form2(Func<String> nameResolver) {
form3 = new Form3(nameResolver);
}
void button1_Click(...) {
form3.Show()
}
}
class Form3 : Form {
Func<String> nameResolver;
public Form3(Func<string> nameResolver) {
this.nameResolver = nameResolver;
}
void button1_Click(...) {
this.textBoxName = nameResolver.Invoke();
}
}
If you end up requiring more than one or two components shared between the various forms, it might be better to simply pass the forms themselves to child forms. Eg.
void button1_Click(...) {
form2 = new Form2(this);
}
class Form2 : Form {
Form1 parent;
public Form2(Form1 parent) {
this.parent = parent;
}
void button1_Click(...) {
form3 = new Form3(parent);
}
}