C＃我不能以其他形式打印可变文本

Question

I trying to code program and I have two forms (Form1 is for loging and Form2 is empty for now, but I would like to print Logged: 'Name' + 'Surename' from DB).

I created class User which has Name and Surename (both public static strings) and method GetUserInfo() to get Name and Surename by user's Login. If I print User.Name + User.Surename in MsgBox after program checks login and password everything is ok, but after Form2 loads then

label1.Text = "User: " + User.name + " " + User.surename;

in method public Form2() shows just User: and nothing more.

Form1:

 public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void textBox1_TextChanged(object sender, EventArgs e)
    {

    }

    private void textBox2_TextChanged(object sender, EventArgs e)
    {

    }

    private void button1_Click(object sender, EventArgs e)
    {

        string login = textBox1.Text;
        string pass = textBox2.Text;

        SqlConnection connection = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\xxx\Documents\Visual Studio 2015\Projects\*\*\Database1.mdf;Integrated Security=True;Connect Timeout=30");
        SqlCommand query = new SqlCommand("Select * from Users where login='" + login + "' AND password ='" + pass + "'", connection);

        connection.Open();


        SqlDataReader Reader = query.ExecuteReader();

        int count = 0;

        Form1 form1 = new Form1();
        Form2 form2 = new Form2();

        while (Reader.Read())
        {
            count += 1;
        }

        if (count == 1)
        {
            this.Hide();
            form2.Show();

            User.GetUserInfo(login);

            MessageBox.Show(User.name + " " + User.surename);
        }
        else
            MessageBox.Show("Bad Login");
    }
}

Form2

public partial class Form2 : Form
{
    public Form2()
    {
        InitializeComponent();

        label1.Text = "User: " + User.name + " " + User.surename;
    }

    private void label1_Click(object sender, EventArgs e)
    {

    }

    private void label1_Click_1(object sender, EventArgs e)
    {

    }
}

and User class:

    public class User
{
    public static string name { get; set; }
    public static string surename { get; set; }

    public static void GetUserInfo(string login)
    {


        using (SqlConnection connection = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\xxx\Documents\Visual Studio 2015\Projects\*\*\Database1.mdf;Integrated Security=True;Connect Timeout=30"))
        using (SqlCommand query = new SqlCommand("Select FirstName, LastName from Users where login='" + login + "'", connection))
        {
            connection.Open();


            SqlDataReader Reader = query.ExecuteReader();

            while (Reader.Read())
            {
                User.name = Reader["FirstName"].ToString();
                User.surename = Reader["LastName"].ToString();
            }
        }
    }
}

Thank you!

Answer 1

Add public variables or properties to Form1 so that you can access them:

in Form1:

public User user; 
....
user.name = Textbox1.Text; 
user.surname = Textbox2.Text; 

In your Form2:

Form frm = new Form1();
frm.ShowDialog();
label1.Text = "User: " + frm.user.name + " " + frm.user.surename;
frm.Dispose();

Answer 2

You are setting the label text in the constructor of Form2 . At that point they don't have a value as you haven't read the data from the database yet, so the label will simply read:

User:

It won't change until you update it's value again. You need to call a method on Form2 to update the label text once the call to User.GetUserInfo has completed successfully.

    if (count == 1)
    {
        this.Hide();
        form2.Show();

        User.GetUserInfo(login);

        // Update the label text here

        MessageBox.Show(User.name + " " + User.surename);

or swap the order of getting the user information and constructing Form2 :

    if (count == 1)
    {
        this.Hide();

        User.GetUserInfo(login);
        form2 = new Form2();
        form2.Show();

Either way will work, the one you choose depends on what else you need to do with your forms.

Answer 3

Use this code:

User.GetUserInfo(login);    
this.Hide();
Form2 form2 = new Form2();
form2.Show();

because you need first set values for name and surename and then use it.

In your case, you first show Form2 and then set values

Answer 4

So the problem you have is that you are creating Form2 before the properties in the User class are filled.

This is why :

label1.Text = "User: " + User.name + " " + User.surename;

This is called inside the constructor of Form2 . This means whenever you initialize this form with

Form2 form2 = new Form2(); 

all code in the constructor executes. So the label text will be set when creating the form.

User.GetUserInfo(login); is called after this, the data will be empty for Form2 since the form is already created.

A possible solution would be

To set the label in the form2 loading event and call User.GetUserInfo(login); before form2.Show();

or

Calling Form2 form2 = new Form2(); after User.GetUserInfo(login);