Question

I have 2 WinForms where one is parent and passing parameter to it’s chilf form. The code goes something like this:

public class FormMain : Form {
private User user;

public FormMain (User user) {
InitializeComponent();
this.user = user;
}

private void btnUpdateAccount_Click(object sender, EventArgs e)
        {
            updateUser = new FormUsersUpdate(user);
            updateUser.Show();
        }
}

and this:

public class FormUsersUpdate(User user){

//Update user in database

}

User class have some usual properties like Name, surname, etc. So my question is how to inform parent class about this update without need to again retrieve user from database?

Thanks.

Answer 1

You can invoke a callback delegate after the update. In FormMain:

private void btnUpdateAccount_Click(object sender, EventArgs e)
{
    updateUser = new FormUsersUpdate(user, new Action<User>(OnUserUpdated));
    updateUser.Show();
}

private void OnUserUpdated(User user)
{
    // Whatever you wanted to do with the updated user.
}

In FormUsersUpdate:

public class FormUsersUpdate(User user, Action<User> callback)
{
    // Update user, then invoke the callback using the updated user instance,
    // which will call the OnUserUpdated method of the FormMain:
    callback.Invoke(user);
}

ShowDialog is mostly a better choice but I never tried it on an mdi child:

private void btnUpdateAccount_Click(object sender, EventArgs e)
{
    updateUser = new FormUsersUpdate(user);
    updateUser.ShowDialog();

    // Will wait until the user closes the dialog box.
    // FormUserUpdate keeps the updated user in a property called User:
    OnUserUpdated(updateUser.User);
}