Storing value before passing to another form later

Question

I am currently working on a C# visual studio windows application. I am having a problem to take a textbox value from one form (Form1) and storing it in a variable for usage in the next form (Form2). I do not want to display the value immediately, therefore i need a way that can store the value in the background and able to use it later on. How can i do it?

I have tried this way but it does not work, anyone can tell me why? The return value in form2 is blank.

Login.cs (Login Page)

    public string uname;

    private void LoginButton_Click(object sender, EventArgs e)
    {
        string userName = this.LoginUsernameTextBox.Text;
        uname = userName;
    }

Form2.cs

    private void CheckLoginUsername_Click(object sender, EventArgs e)
    {
    Login login = new Login();
    MessageBox.Show("The value of uname is:" + login.uname);
    }

Answer 1

The problem is that Form2 isn't referencing the same instance of Login that the user is interacting with, you're creating a new instance (never showing it to the user) and then grabbing a value out of that.

You haven't shown the extent of the interactions between these forms (and if you have, you're missing a fair bit).

It should likely look something like this:

In Form2:

private void Form1_Load(object sender, EventArgs e)
{
    Login loginForm = new Login ();

    loginForm.ShowDialog();

    string username = loginForm.UserName;
}

Then the login form should have something like this:

public string UserName { get; private set; }

That will allow you to set the value internally (when the form is submitted/closed) and read it externally.

It's considered poor practice for fields to be public; it's preferable to use properties instead (so that, among other things, you can do what I have done here and restricted the setter to be private).