How can I exchange data between forms [duplicate]

Answer 1

You could do something like the following. It assumes that you've created a form called SomeForm and have added a constructor that accepts a string to it.

    public partial class LoginForm : Form
    {
        private string somedata = "somedata";

        public LoginForm()
        {
            InitializeComponent();

            OpenForm(somedata);
        }    
    }

    private void OpenForm(string Data)
    {
        SomeForm sf = new SomeForm(Data);
        sf.Show();
    }

Answer 2

First create a public string on your second form you want to pass the data from login:

   public partial class Form2 : Form       
 {  

 public Form2()              
{  
InitializeComponent(); 
}  

    public string messagefromLogin;
    MessageBox.Show(messagefromLogin);

    }

then on your login:

 public partial class LoginForm : Form       
 {  

 public LoginForm()              
{  
InitializeComponent(); 
}   
private string somedata = "somedata";

//Show Form2 and pass the string "somedata"
 private void btnShowForm2_Click(object sender, EventArgs e)
        {
            var frm2 = new Form2{messagefromLogin=somedata}
frm2.Show();
        }

}

Regards

Answer 3

there are many ways,

Pass a reference of your parent form to your child or just pass the data to the child form in the constructor or the set a property.

protected void viewHelp(){
  var loginHelp = new LoginHelpForm();
  loginHelp.ParentForm = this;
  loginHelp.Show(); 
  this.Hide();
}