i need help on using web browser

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i use web browser,i can navigate to site but i can't change elements value like text boxes.

i use this code to fill google text box and click on search button:

C#

private void button1_Click(object sender, EventArgs e)
{
         webBrowser1.Navigate("google.com"); 
         webBrowser1.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(web_h);
}
private void web_h(object sender, WebBrowserDocumentCompletedEventArgs e)
{
           WebBrowser b = (WebBrowser)sender;
           b.Document.GetElementById("gbqfq").InnerText = "programming"; 
           b.Document.GetElementById("gbqfba").InvokeMember("click");
}

but i face with this error: System.NullReferenceException

can you help me?

Posted 4-Jul-14 2:28am

Abolfazl_d_sh

Updated 4-Jul-14 2:34am

Thanks7872

v2

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CHill60 · Answer 1 · 2014-07-04T02:52:00

You are getting the error on line

b.Document.GetElementById("gbqfq").InnerText = "programming";

This is because there is no Element called gbqfq so

b.Document.GetElementById("gbqfq")

is null.
You can't assign values to properties (e.g. .InnerText) of null objects.

You need to check for success find first e.g.

C#

private void web_h(object sender, WebBrowserDocumentCompletedEventArgs e)
{
    WebBrowser b = (WebBrowser)sender;
    HtmlElement  h1 = b.Document.GetElementById("gbqfq");
    if (h1 != null)
        h1.InnerText = "programming";
    h1 = b.Document.GetElementById("gbqfba");
    if (h1 != null)
        h1.InvokeMember("click");
}