Evaluating string "3*(4+2)" yield int 18 [duplicate]

Solution 1:

If you want to evaluate a string expression use the below code snippet.

using System.Data;

DataTable dt = new DataTable();
var v = dt.Compute("3 * (2+4)","");

Solution 2:

Using the compiler to do implies memory leaks as the generated assemblies are loaded and never released. It's also less performant than using a real expression interpreter. For this purpose you can use Ncalc which is an open-source framework with this solely intent. You can also define your own variables and custom functions if the ones already included aren't enough.

Example:

Expression e = new Expression("2 + 3 * 5");
Debug.Assert(17 == e.Evaluate());

Solution 3:

Try this:

static double Evaluate(string expression) {
  var loDataTable = new DataTable();
  var loDataColumn = new DataColumn("Eval", typeof (double), expression);
  loDataTable.Columns.Add(loDataColumn);
  loDataTable.Rows.Add(0);
  return (double) (loDataTable.Rows[0]["Eval"]);
}

Solution 4:

You could look at "XpathNavigator.Evaluate" I have used this to process mathematical expressions for my GridView and it works fine for me.

Here is the code I used for my program:

public static double Evaluate(string expression)
{
    return (double)new System.Xml.XPath.XPathDocument
    (new StringReader("<r/>")).CreateNavigator().Evaluate
    (string.Format("number({0})", new
    System.Text.RegularExpressions.Regex(@"([\+\-\*])")
    .Replace(expression, " ${1} ")
    .Replace("/", " div ")
    .Replace("%", " mod ")));
}