. 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());

}

. 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());

}

. 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);

}

. 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 + "");

}