Passing Values Between Windows Forms C#

Passing Values Between Windows Forms c#

You need to put loginData into a local variable inside the frmVoiceOver class to be able to access it from other methods. Currently it is scoped to the constructor:

class frmVoiceOver : Form
{
    private NewDataSet _loginData;

    public frmVoiceOver(NewDataSet loginData)
    {
        _loginData = loginData;

        InitializeComponent();
    }

    private void btnVoiceOverNo_Click(object sender, EventArgs e)
    {
        // Use _loginData here.
        this.Close();
        Form myFrm = new frmClipInformation();
        myFrm.Show();
    }
}

Also, if the two forms are in the same process you likely don't need to serialize the data and can simply pass it as a standard reference to the form's constructor.

Google something like "C# variable scope" to understand more in this area as you will encounter the concept all the time. I appreciate you are self-taught so I'm just trying to bolster that :-)

Passing data between C# forms

The code that you put in the sample project (that you provided as a link in the comments) should be in your question. Given that it becomes much easier to understand what you're trying to do and to give you a workable solution.

I would suggest creating a "DataTransferObject" and pass that between each form.

public class Dto
{
    public string Text;
}

The code in MainWindow would then look like this:

    private void button1_Click(object sender, RoutedEventArgs e)
    {
        var dto = new Dto();
        window2 win2 = new window2();
        win2.Dto = dto;
        win2.ShowDialog();
        textBox1.Text = dto.Text;
    }

And the code in window2 would look like this:

    public Dto Dto;

    private void textBox2_TextChanged(object sender, TextChangedEventArgs e)
    {
        if (this.Dto != null)
        {
            this.Dto.Text = textBox2.Text;
        }
    }

That is one way - out of about a million - of transferring data between forms. An advantage of using a data transfer object is that it begins you on the road of separating your data from your UI, and that is generally a very good thing to do.

Passing data between forms

Form1 frm = new Form1();

frm is now a new instance of class Form1.

frm does not refer to the original instance of Form1 that was displayed to the user.

One solution is, when creating the instance of Form2, pass it a reference to your current instance of Form1.

Passing values between Windows form and a database

An example of an alternative to the DB connection you have made is below

  List<MyPhone> myIPhoneList = new List<Myphone>();
   List<MyPhone> myAndroidList = new List<Myphone>();

SqlConnection myDBConnection = new SqlConnection("MyConnectionString"); //DB Connection
            SqlCommand dbCommand = new SqlCommand("SelectAllPhones"); //Stored Procedure
            SqlDataReader recordReader = dbCommand.ExecuteReader(); //Execute

            //Read records return in to phone objects
            while (recordReader.Read()) {
                var phoneField1 = recordReader["PhoneField1FromDatabase"];
                var phoneField2 = recordReader["PhoneField2FromDatabase"];
                //etc...

                var myPhone = new MyPhone();
                myPhone.Name = phoneField1;
                //etc...
                if (myPhone.OS == "iPhone")
                 myIPhoneList.Add(myPhone);

               if (myPhone.OS = "Android")
                 myAndroidList.Add(myPhone);
            }

Pass data between 2 already OPEN winforms (C#)

You can use events to pass messages to disconnected entities. You can listen for events in Form1 and raise them from Form2. This is from memory, don't fully expect it to compile.

Create a class that is the "event hub".

public static class EventHub
{
    public static event EventHandler<EventArgs> formMessageHandler;

    public static void OnFormMessage(object sender, EventArgs e)
    {
        formMessageHandler?.Invoke(sender, e);
    }
}

In Form2 button click event raise the event. You can use the sender reference directly to access public members or you can put relevant data into an EventArgs.

EventHub.OnFormMessage(this, EventArgs.Empty);

In Form1, maybe in the constructor, wire up a listener:

EventHub.formMessageHandler += some_method_you_write;

Now, when you click the button in Form2, Form1 will receive a reference to Form2 in some_method_you_write(). Or, you can actually use the EventArgs to pass data so you don't need to make any public controls on Form2.

Passing Values from one Form to another Form in a Button click

Actually I have an object to pass. So I did this

in form1-->

private void btnOpenF2_Click(object sender, EventArgs e)
        {
            new Form2(this).Show();
        }

in form2-->

public partial class Form2 : Form
    {
        Form1 a;
        public Form2(Form1 b)
        {
            a = b;
            InitializeComponent();

        }
        private void button1_Click(object sender, EventArgs e)
        {
            string g;
            g = textBox1.Text;


            a.set(g);
            this.Close();
        }
    }

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