title: How to send value of textBox to string variable?
body: <p>How to send value of textBox to string variable?</p>
  
  <p>I have View with html:</p>
  
  <pre><code>&lt;body&gt;
  &lt;div id="CalculatorSpace"&gt;
      &lt;form name="Calc"&gt;
          &lt;input type="text" name="textBox" id="textBox" value=""/&gt;
          &lt;table&gt;
              &lt;tr&gt;
                  &lt;td&gt;&lt;input type="button" name="btnSeven" id="btnSeven" value="7" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnEight" value="8" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnNine" value="9" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnDelete" value="DEL" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnClear" value="CLR" /&gt;&lt;/td&gt;
              &lt;/tr&gt;
              &lt;tr&gt;
                  &lt;td&gt;&lt;input type="button" id="btnFour" value="4" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnFive" value="5" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnSix" value="6" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnMultiply" value="*" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnDivide" value="/" /&gt;&lt;/td&gt;
              &lt;/tr&gt;
              &lt;tr&gt;
                  &lt;td&gt;&lt;input type="button" id="btnOne" value="1" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnTwo" value="2" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnThree" value="3" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnPlus" value="+" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnMinus" value="-" /&gt;&lt;/td&gt;
              &lt;/tr&gt;
              &lt;tr&gt;
                  &lt;td&gt;&lt;input type="button" id="btnZero" value="0" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnDot" value="." /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnEqual" value="=" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnLBracket" value="(" /&gt;&lt;/td&gt;
                  &lt;td&gt;&lt;input type="button" id="btnRBracket" value=")" /&gt;&lt;/td&gt;
              &lt;/tr&gt;
          &lt;/table&gt;
          &lt;script&gt;
              window.onload = function () {
                  document.getElementById('btnSeven').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnSeven').value;
                  });
                  document.getElementById('btnEight').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnEight').value;
                  });
                  document.getElementById('btnNine').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnNine').value;
                  });
                  document.getElementById('btnDelete').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnDelete').value;
                  });
                  document.getElementById('btnClear').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnClear').value;
                  });
                  document.getElementById('btnFour').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnFour').value;
                  });
                  document.getElementById('btnFive').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnFive').value;
                  });
                  document.getElementById('btnSix').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnSix').value;
                  });
                  document.getElementById('btnMultiply').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnMultiply').value;
                  });
                  document.getElementById('btnDivide').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnDivide').value;
                  });
                  document.getElementById('btnOne').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnOne').value;
                  });
                  document.getElementById('btnTwo').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnTwo').value;
                  });
                  document.getElementById('btnThree').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnThree').value;
                  });
                  document.getElementById('btnPlus').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnPlus').value;
                  });
                  document.getElementById('btnMinus').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnMinus').value;
                  });
                  document.getElementById('btnZero').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnZero').value;
                  });
                  document.getElementById('btnDot').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnDot').value;
                  });
                  document.getElementById('btnEqual').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnEqual').value;
                  });
                  document.getElementById('btnLBracket').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnLBracket').value;
                  });
                  document.getElementById('btnRBracket').addEventListener('click', function () {
                      document.getElementById('textBox').value = document.getElementById('textBox').value + document.getElementById('btnRBracket').value;
                  });
              }
          &lt;/script&gt;
      &lt;/form&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p></p>
  
  <p>And I have Controller:</p>
  
  <pre><code>public class CalculatorController : Controller
  {
      //
      // GET: /Calculator/
      public ActionResult Index()
      {
          return View();
      }
      //GET: /Calculator/Calculate
      public ActionResult Calculate()
      {
          string expression;
          return View();
      }
  }
  </code></pre>
  
  <p>Now what I want is to send value of textBox to string expression, pars the expression like "5+5" and send value result to the textBox. Everything must be done by one clicking on button btnEqual. How to do that?</p>