I had to try it for myself so here is your code ported to C#. It worked as advertised for me:

[font="Courier New"]using System;

using System.Data;

using System.Data.SqlClient;

using System.Data.SqlTypes;

using Microsoft.SqlServer.Server;

public partial class UserDefinedFunctions

{

    [Microsoft.SqlServer.Server.SqlFunction]

    public static SqlString stringEval(string equation)

    {

        DataTable table = new DataTable();

        object eqObject;

        eqObject = table.Compute(equation, "");

        SqlString results = SqlDecimal.Parse(eqObject.ToString()).ToString();

        return results;

    }

};

[/font]