Invoke button click programmatically

Question

I want to programmatically click button on a webpage with source like this

<input alt="BusiBtn" class="aButtn" type="submit" value="Search" tabindex="16">

When I do

WebBrowser b = new WebBrowser();
b.Navigate(URL);
while (b.ReadyState != WebBrowserReadyState.Complete)
{
   Application.DoEvents();
}
b.Document.GetElementByID("BusiBtn").InvokeMember("click");

I get "Object reference not set to an instance of object error".

Can somebody help.

Thanks Rashmi

Please, do not include information about a language used in a question title unless it wouldn't make sense without it. Tags serve this purpose. — Ondrej Janacek
– Ondrej Janacek, Commented Mar 9, 2014 at 12:19

Wasif Hossain · Accepted Answer · 2014-03-10 03:12:31Z

2

What you can do in this case simply find all the HtmlElements having input tag. If you need to invoke all the input tags in general, then just invoke click on them. And if you need only the above input element, then filter all the input tags to search for the specific tag with the attribute values like above. Please have a look at the following code:

HtmlElementCollection elems = b.Document.GetElementsByTagName("input");

foreach (HtmlElement elem in elems)
{
    string altStr = elem.GetAttribute("alt");
    string classStr = elem.GetAttribute("class");
    string typeStr = elem.GetAttribute("type");
    string valueStr = elem.GetAttribute("value");
    string tabindexStr = elem.GetAttribute("tabindex");

    if((altStr == "BusiBtn") && (classStr == "aButtn") && (typeStr == "submit") && (valueStr == "Search") && (tabindexStr == "16"))
    {
        elem.InvokeMember("click");
        break;
    }
}

edited Mar 10, 2014 at 3:12

answered Mar 10, 2014 at 2:52

Wasif Hossain

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Comments

Moo-Juice · Accepted Answer · 2014-03-09 12:17:54Z

1

You're using the wrong field.

alt is for alternative text.

You have not actually given that button an id of BusiBtn.

Try:

<input id="BusiBtn" class="aButtn" type="submit" value="Search" tabindex="16">

The clue is in the GetElementByID call. It's not called GetElementByAlt for a reason ;)

answered Mar 9, 2014 at 12:17

Moo-Juice

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2 Comments

Rashmi Over a year ago

That's what the source looks like. How can I invoke the button without the ID?

Moo-Juice Over a year ago

if the element has no id, then GetElementByID will not work for you. Use another method that is available that can match a known value.

James Aster · Accepted Answer · 2014-03-09 12:57:13Z

1

add 'name' property to input tag and then use GetElementsByName property

answered Mar 9, 2014 at 12:57

James Aster

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1 Comment

Rashmi Over a year ago

This is not our website. I am crawling somebody's website and want to programmatically download info by clicking the button.

IliaJ · Accepted Answer · 2014-03-10 01:41:43Z

0

You should use the GetElementsByTagName method instead of GetElementById to get all Input-Elements on the page and then cycle through using GetAttribute. An example can be found here http://msdn.microsoft.com/en-us/library/system.windows.forms.htmldocument.getelementsbytagname(v=vs.110).aspx.

answered Mar 10, 2014 at 1:41

IliaJ

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