youtube - Null Value from GetElementById using C# -

i've gone through loads of asked questions haven't been able find solution problem.

my application video finder, user enters he/she looking in textbox , selects 1 of 3 websites(youtube,metacafe,screen.yahoo) find video.

ive got method each of choices when reaches getelementbyid method returns null value three. im going assume ive missed , thats why im having null result 3 methods.

firstly here youtube method

private void youtube(string input)         {             try             {                 webbrowser1.navigate("https://www.youtube.com/");                 htmldocument doc = webbrowser1.document;                 htmlelement search = doc.getelementbyid("search_query");                 search.setattribute("value",input);             }             catch(exception ex)             {                 messagebox.show(ex.message.tostring(), "error");             }          } 

here elements search bar(from youtube) i'm trying access.

<input id="masthead-search-term" autocomplete="off" autofocus="" onkeydown="if (!this.value &amp;&amp; (event.keycode == 40 || event.keycode == 32 || event.keycode == 34)) {this.onkeydown = null; this.blur();}" class="search-term masthead-search-renderer-input yt-uix-form-input-bidi" name="search_query" value="" type="text" tabindex="1" placeholder="" title="search" dir="ltr" spellcheck="false" style="outline: none;"> 

i've tried both id , name element both have given me same result.

not sure weather need other 2 methods seeing identical i'm going post them incase.

here metacafe element

private void metacafe(string input)         {             try             {                 webbrowser1.navigate("http://www.metacafe.com/");                 htmldocument doc = webbrowser1.document;                 htmlelement search = doc.getelementbyid("searchtext");                 //webbrowser1.document.getelementbyid("searchtext").setattribute("value", input);                 search.setattribute("value", input);             }             catch (exception ex)             {                 messagebox.show(ex.message.tostring(), "error");             }          } 

and element im trying connect to.

<input value="search metacafe" type="text" accesskey="s" class="textfield " title="search metacafe" autocomplete="off" size="50" name="searchtext" tabindex="1" id="searchquery"> 

lastly yahoo method.

private void yahoo(string input)         {             try             {                 webbrowser1.navigate("https://screen.yahoo.com/");                 htmldocument doc = webbrowser1.document;                 htmlelement search = doc.getelementbyid("p");                 search.setattribute("value", input);             }             catch (exception ex)             {                 messagebox.show(ex.message.tostring(), "error");             }          } 

and element.

<input id="uhsearchbox" type="text" class="yucs_w(100%) fz(18px)! o(n):f fw(200)! bxz(bb) m(0)! py(4px)! bdrs(0)! bxsh(n)" style="border-color: rgb(117, 144, 245); opacity: 1;" name="p" aria-describedby="uhsearchbox" data-ylk="slk:srchinpt-hddn;itc:1;" data-yltvsearch="https://video.search.yahoo.com/search/" data-yltvsearchsugg="/" data-satype="mini" data-gosurl="https://search.yahoo.com/sugg/ss/gossip-us_ss/" data-pubid="112" data-appid="" data-maxresults="10" data-resize=" " data-rapid_p="2"> 

thanks taking time read it. /d

you trying find element id in method getelementbyid() giving name of element need find element it's id this

htmlelement search = doc.getelementbyid("masthead-search-term"); 

do same rest of two.

also element null if page hasn't loaded can access element after page has loaded completely.

edit

you need add documentcompleted event of webbrowser. event occurs when webbrowser has finished loading document.

 private void youtube(string input)     {         try         {             webbrowser1.documentcompleted += webbrowser1_documentcompleted;             webbrowser1.navigate("https://www.youtube.com/");          }         catch(exception ex)         {             messagebox.show(ex.message.tostring(), "error");         }      } void webbrowser1_documentcompleted(object sender, webbrowserdocumentcompletedeventargs e)     {         htmldocument doc = webbrowser1.document;         htmlelement search = doc.getelementbyid("search_query");         search.setattribute("value",input);     }