Evaluate string expression C#

public static double Evaluate ( string expression )
{
// That is some code instruction, is'nt it? :)
return (double) new System.Xml.XPath.XPathDocument
( new StringReader("")).CreateNavigator().Evaluate
( string.Format("number({0})", new
System.Text.RegularExpressions.Regex(@"([\+\-\*])")
.Replace(expression, " ${1} ")
.Replace("/", " div ")
.Replace("%", " mod ") ) );
}