Wait for the page to load in web browser control mode

I am using a C # WebBrowswer control, and I have a problem when, when I click a button, such as "Next", when the page is not already loaded, the program tries to continue, but instead gives me a zero error.

Is there a function for the program to wait for the page to load?

I tried to put a while loop in a program that checks the title of an html page, but then the program freezes. Something like freezing a program:

    while(!webbrowser1.Document.Title.ToString().Equals("NextPageTitle"))
   {
   }
   ::NextCommands::

It does not work, I tried this and the "fblqf" button is not pressed. but does not return a null error.

public void button1_Click(object sender, EventArgs e)
{



    webBrowser1.Document.GetElementById("q").SetAttribute("value", "חחח");
    webBrowser1.Document.GetElementById("btnK").InvokeMember("Click");
    webBrowser1.DocumentCompleted += webBrowser1_DocumentCompleted;


}
void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
    // do the work you need to do now that that page has completed loading
    webBrowser1.Document.GetElementById("fblqf").InvokeMember("Click");
}

Decision:

public void button1_Click(object sender, EventArgs e)
{
    webBrowser1.Document.GetElementById("q").SetAttribute("value", "חחח");
    webBrowser1.Document.GetElementById("btnK").InvokeMember("Click");
    int x=0;
    while (x==0)
   {
       System.Windows.Forms.Application.DoEvents();
        if(webBrowser1.Document.GetElementById("pnnext") != null)
        break;
   }

    webBrowser1.Document.GetElementById("pnnext").InvokeMember("Click");
    webBrowser1.Document.GetElementById("q").Focus();
}