C# - passing a variable to another form-CodePudding

I am trying to pass a User user variable to another form, but for some reason it says that it's value is null. What did I do wrong?

AuthorizationForm.cs:

public partial class AuthorizationForm : Form
{
        public Model.User user;

        private void loginButton_Click(object sender, EventArgs e)
        {
            user = mCollection.Find(u => u.Email == loginBox.Text).FirstOrDefault();
            // Logic, which shows, that in this scope user is not null
        }
}

MainForm.cs:

public partial class MainForm : Form
{
        View.AuthorizationForm authorizationForm = new View.AuthorizationForm();

        private void confirmButton_Click(object sender, EventArgs e)
        {
            // NullReferenceException thrown here because `authorizationForm.user` is null.
            MessageBox.Show(authorizationForm.user.Name);
        }
}

CodePudding user response：

Try adding constructors to AuthorizationForm

public partial class AuthorizationForm : Form
{
        public Model.User user;

        public AuthorizationForm()  
        {  
            InitializeComponent();
        }

        private void loginButton_Click(object sender, EventArgs e)
        {
            user = mCollection.Find(u => u.Email == loginBox.Text).FirstOrDefault();
            // Logic, which shows, that in this scope user is not null
        }
}

CodePudding user response：

You can pass the input variable to the constructor when creating an instance of the AuthorizationForm class.

public partial class AuthorizationForm : Form
{
      public Model.User user;
      public AuthorizationForm(Model.User _user)
      {
          user = _user;
      }   

      private void loginButton_Click(object sender, EventArgs e)
      {
          user = mCollection.Find(u => u.Email == loginBox.Text).FirstOrDefault();
          // Logic, which shows, that in this scope user is not null
      }
}

Or in the first form the user variable separately

public partial class MainForm : Form
{
        View.AuthorizationForm authorizationForm = new View.AuthorizationForm();
        authorizationForm.user = yourVaule
        //...................................................
}