How to pass data from parent form to the child form in c# winform

Question

I am trying to pass some strings(device info) from the parent form(the main form )in MDI to the child form

• The child form displays

1. Device name
2. Device model number
3. Manufactured date,

• All these features should be passed to the child form when the ON button in the parent form is being clicked.
• The child form is called through the menu.
• Till now I have had success in only calling the child through the menu but cannot pass the data.

Parent Form: menu to view the child form on the MDI(parent form) whenever I want to

private void DeviceInfomationToolStripMenuItem_Click(object sender, EventArgs e)
        {
            if (Application.OpenForms["Child"] is Child deviceInfo)
            {
                deviceInfo.Focus();
                return;
            }
            deviceInfo = new Child();
            deviceInfo.MdiParent = this;
            deviceInfo.Show();
        }

Parent From: On button event

private void btnOn_Click(object sender, EventArgs e)
        {
            deviceName = "Notebook520220624";
            deviceModel =  "520220627";
            manuFacturedDate = "220627";
            Child form = new Child(deviceName);
        }

Child Form: Receiving the device info and displaying it

public Child(string deviceName)
{
  InitializeComponent();
  name_lbl.Text = deviceName
  //name_lbl.Text = deviceName.ToString();
  //model_lbl.Text = diviceModel;
  //date_lbl.Text = manuFacturedDate;
}

Answer 1

You can declare static variable in parent form outside your method,in class level - global scope, and then access that variable through the type in your child form constructor, so for example

public static string deviceName = ""; // Here I declared static string global variable, and initialized to empty string

    private void btnOn_Click(object sender, EventArgs e)
            {
                deviceName = "Notebook520220624"; // Assign the value to variable
                deviceModel =  "520220627";
                manuFacturedDate = "220627";
            }

And then, in your child form, you can pass the value of static variable to your textbox through the default constructor, by calling this

public Child()
{
  InitializeComponent();
  name_lbl.Text = ParentForm.deviceName; // Here I put name ParentForm type name regarding to this example, but you should change according to your name of your class
}