Is there a string math evaluator in .NET?

Question

If I have a string with a valid math expression such as:

String s = "1 + 2 * 7";

Is there a built in library/function in .NET that will parse and evaluate that expression for me and return the result? In this case 15.

Answer 1

Strange that this famous and old question has not an answer that suggests the builtin DataTable.Compute-"trick". Here it is.

double result = Convert.ToDouble(new DataTable().Compute("1 + 2 * 7", null));

The following arithmetic operators are supported in expressions:

+ (addition)
- (subtraction)
* (multiplication)
/ (division)
% (modulus)

More informations: DataColumn.Expression at Expression Syntax.

Answer 2

You could add a reference to Microsoft Script Control Library (COM) and use code like this to evaluate an expression. (Also works for JScript.)

Dim sc As New MSScriptControl.ScriptControl()
sc.Language = "VBScript"
Dim expression As String = "1 + 2 * 7"
Dim result As Double = sc.Eval(expression)

Edit - C# version.

MSScriptControl.ScriptControl sc = new MSScriptControl.ScriptControl();
sc.Language = "VBScript";
string expression = "1 + 2 * 7";
object result = sc.Eval(expression);            
MessageBox.Show(result.ToString());

Edit - The ScriptControl is a COM object. In the "Add reference" dialog of the project select the "COM" tab and scroll down to "Microsoft Script Control 1.0" and select ok.

Answer 3

For anybody developing in C# on Silverlight here's a pretty neat trick that I've just discovered that allows evaluation of an expression by calling out to the Javascript engine:

double result = (double) HtmlPage.Window.Eval("15 + 35");