原地址:https://blog.csdn.net/ifu25/article/details/53292134

四种方式

• 简单粗暴：利用SQL数据库计算
• 功能强大：利用JavaScript计算
• 看不懂：后序式计算
• 简单好用：DataTable的Compute方法

代码

1. SQL方式

/// <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());
}
 

2. JScript

/// <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());
}


3. 中序式转换成后序式

/// <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);
}
4. 由DataTable计算公式

/// <summary>
/// 由DataTable计算公式
/// </summary>
/// <param name="expression">表达式</param>
internal static float CalcByDataTable(string expression)
{
    object result = new DataTable().Compute(expression, "");
    return float.Parse(result + "");
}