How I can make a web scraping putting captcha image in my web app to query?

I've been trying to do the following:

Make web scraping to a page that has captcha.

Put its picture with the code captha on my website to be entered by the user making the request.

But I have encountered the following, the product generates the following touch:

<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUJMTY3ODU1NDM3D2QWAgIBD2QWAgIBD2QWAgIED2QWAgIBD2QWAgIBD2QWAgIDDw8WBh4JRm9yZUNvbG9yDB4EVGV4dAU0SW50cm9kdXpjYSBsb3MgbsO6bWVyb3MgcXVlIHNlIG11ZXN0cmFuIGVuIGxhIGltYWdlbh4EXyFTQgIEZGRkI2vSAHfBwff4bQeYBeNrp2LgasjW5sAD/qaJaVX0FpI=">

<input type="hidden" name="__VIEWSTATEGENERATOR" id="__VIEWSTATEGENERATOR" value="CA0B0334">
<input type="hidden" name="__EVENTVALIDATION" id="__EVENTVALIDATION" value="/wEdAAUwHk+inUhBKZDyswsk5NNZgR+Ryzr40mCfb2xFWNvaXeZZujVI1Q63igKvL1NytQuECrD8jc5xpRI7GCI9w78rcjH6FuL/XcvxzPKyRvH3SBFX/SsuYstDGgj/PHztePFe/30iEMMQ1c1DxkjUszAx">

I take hours trying to do this but I'm seeing impossible. To provide the data I'm doing the following:

string strURL;
            string strPostData = "";
            string strResult;
            HttpWebResponse webrespond;
            HttpWebRequest webresquest;
            StreamReader sr;
            StreamWriter sw;

            //set url to post
            strURL = "http://ift.tt/1NiFHJH";

            //post some data        
            strPostData = "txtCodigo=001123458&CaptchaImage1$CodeNumberTextBox=9563";

            webresquest = (HttpWebRequest)WebRequest.Create(strURL);
            webresquest.Method = "POST";
            webresquest.Referer = strURL;
            webresquest.ContentType = "application/x-www-form-urlencoded";
            webresquest.ContentLength = strPostData.Length;

            //post data
            sw = new StreamWriter(webresquest.GetRequestStream());
            sw.Write(strPostData);
            sw.Close();

            //read the returned data
            webrespond = (HttpWebResponse)webresquest.GetResponse();
            sr = new StreamReader(webrespond.GetResponseStream());
            strResult = sr.ReadToEnd();          
            sr.Close();
            return strResult

;

thanks :)