Element “webBrowser”. How to wait for the page to load?

Question

Document structure
"Form0" - Form
- - "panel2" - Panel
- - - "Frm5UC" - Custom item
- - - - "webBrowser1" - Browser

Application logic:
- go to the page in "webBrowser1";
- enter login;
- enter the password;
- click the "Login" button.

If I execute the logic through the code (this is the "Method_0 ()" method), the form does not have time to load in the "Authorization ()" method. I get "webBrowser1.Document = null", error "Object link does not indicate an object instance."

If I do everything through the interface, then everything works.

How to make the logic run programmatically?

 

private void Frm5UC_Load(object sender, EventArgs e)
        {
            webBrowser1.Visible = true;

            // *** TESTS ***
            Method_0();
        }



        #region *** TESTS ***
        public void Method_0()
        {
            Method_1();
            Method_2();
        }

        public void  Method_1()
        {
            textBox2.Text = "_domain_com";
            textBox1.Text = @"domain_com/login/";

            button1.PerformClick();
        }

        public void Method_2() // ???????????
        {
            Authorization();
        }
        #endregion *** TESTS ***


        private void button1_Click(object sender, EventArgs e)
        {
            webBrowser1.Navigate(textBox1.Text);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Authorization();
        }

        public void Authorization() // ???????????
        {
                foreach (HtmlElement he in webBrowser1.Document.GetElementsByTagName("input"))
                {
                    if (he.GetAttribute("name") == "login[login]")
                    {
                        he.SetAttribute("value", "login798");
                    }
                }

            // Code "enter password"
            // Code "Press the button"
        }