c# - WPF Browser throws error -

i calling javascript functions c# using wpf variant of browser control via invokescript.

i can call function once without problems. when call second time, throws following error :

unknown name. (exception hresult: 0x80020006 (disp_e_unknownname))

the code using following :

this.browser.loadcompleted += (sender, args) => {    this.browser.invokescript("writefromexternal", new object[] { "firstcall" }); // works    this.browser.invokescript("writefromexternal", new object[] { "secondcall" }); // throws error }; 

the javascript function :

function writefromexternal(message) {    document.write("message : " + message); } 

i can call c# functions page via javascript fine , invoke c#, can't invoke second time. regardless of function call.

i not understand why fail second time.

thank you

edit :

did following test (javascript) :

        function pageloaded() {             window.external.tick();             window.external.tick();             window.external.tick();         }         window.onload = pageloaded;         function writefromexternal(message) {             document.write("message : " + message);         } 

and c# side :

            private int = 0;             public void tick()             {                 invoke("writefromexternal", new object[] { "ticked"+ i++ });             }             public static void invoke(string method, object[] parameters)             {                 maininterface.browser.invokescript(method, parameters);             } 

and still throws same error (after first call), suggests not matter called, invoking function c# throw error if done more once.

i assume did same me , put scripts in body. reason when call document.write wpf overwrites document. if instead of using document.write append child works fine. change javascript function be:

 window.writefromexternal = function (message) {     var d = document.createelement("div")     d.innerhtml= "message : " + message;     document.body.appendchild(d);  }      // call c#   writefromexternal("test")