C# 自动计算字符串公式的值(三种方式)

C# Code:


/// <summary>
/// C#自动计算字符串公式的值
/// </summary>
public class CalcStringExpression
{
   /// <summary>
   /// 最简单的方式由SQL计算
   /// </summary>
   /// <param name="expression">表达式</param>
   /// <returns></returns>
   public static float CalcBySQL(string expression)
   {
      string SQL = "SELECT " expression " AS RESULT_VALUE";
      SqlConnection conn = new SqlConnection("自己定义连接字符串");
      SqlCommand cmd = new SqlCommand(SQL, conn);
      object o = cmd.ExecuteScalar(); //执行SQL.
      return float.Parse(o.ToString());
   }
   
   /// <summary>
   /// 由Microsoft.Eval对象计算表达式，需要引用Microsoft.JScript和Microsoft.Vsa名字空间。
   /// </summary>
   /// <param name="expression">表达式</param>
   /// <returns></returns>
   public static float CalcByJs(string expression)
   {
      Microsoft.JScript.Vsa.VsaEngine ve = Microsoft.JScript.Vsa.VsaEngine.CreateEngine();
      object returnValue = Microsoft.JScript.Eval.JScriptEvaluate((object)expression, ve);
      return float.Parse(returnValue.ToString());
   }
   
   /// <summary>
   /// 由中序式转换成后序式，再用栈来进行计算
   /// </summary>
   /// <param name="expression">表达式</param>
   /// <returns></returns>
   public static float CalcByCalcParenthesesExpression(string expression)
   {
      string result = new CalcParenthesesExpression().CalculateParenthesesExpression(expression);
      return float.Parse(result);
   }
   
}

//来源:C/S框架网(www.csframework.com) QQ:1980854898