创建动态公式

我需要创建一个用户将构建公式的UI.即:

对于一个项目公式是:

费用*项目/ 100

对于另一个项目:

项目*5/100

我希望用户能够通过web ui生成公式.

然后,当用户输入我想要计算结果的变量时.

有没有任何包或插件来做到这一点？

谢谢.

达斯·维达!

这里有几个选项,它取决于您的需求,是否需要一些非常复杂的东西或者只是简单易懂和扩展的东西(可能用于学术目的).

1)让我们从简单,容易和可定制的开始.我已经创建了一个满足您在帖子中指定的需求的类,但是它非常原始,不应该在没有进一步测试和修改的情况下用于商业项目...如果你可以轻松拿起并增加它想要...它显示了一种实现所需要的简单方法.代码很好地工作但没有考虑数学优先级(例如括号或*over +).它需要进行调整以便这样做......代码在下面,它被评论并希望自我解释:

public class DynamicFormula
{
    /// 

    /// This simply stores a variable name and its value so when this key is found in a expression it gets the value accordingly.
    /// 
    public Dictionary Variables { get; private set; }

    /// 

    /// The expression itself, each value and operation must be separated with SPACES. The expression does not support PARENTHESES at this point.
    /// 
    public string Expression { get; set; }

    public DynamicFormula()
    {
        this.Variables = new Dictionary();
    }

    public double CalculateResult()
    {
        if (string.IsNullOrWhiteSpace(this.Expression))
            throw new Exception("An expression must be defined in the Expression property.");

        double? result = null;
        string operation = string.Empty;

        //This will be necessary for priorities operations such as parentheses, etc... It is not being used at this point.
        List aux = new List();  

        foreach (var lexema in Expression.Split(new string[] { " " }, StringSplitOptions.RemoveEmptyEntries))
        {
            //If it is an operator
            if (lexema == "*" || lexema == "/" || lexema == "+" || lexema == "-")
            {
                operation = lexema;
            }
            else //It is a number or a variable
            {
                double value = double.MinValue;
                if (Variables.ContainsKey(lexema.ToLower())) //If it is a variable, let's get the variable value
                    value = Variables[lexema.ToLower()];
                else //It is just a number, let's just parse
                    value = double.Parse(lexema);

                if (!result.HasValue) //No value has been assigned yet
                {
                    result = value;
                }
                else
                {
                    switch (operation) //Let's check the operation we should perform
                    {
                        case "*":
                            result = result.Value * value;
                            break;
                        case "/":
                            result = result.Value / value;
                            break;
                        case "+":
                            result = result.Value + value;
                            break;
                        case "-":
                            result = result.Value - value;
                            break;
                        default:
                            throw new Exception("The expression is not properly formatted.");
                    }
                }
            }
        }

        if (result.HasValue)
            return result.Value;
        else
            throw new Exception("The operation could not be completed, a result was not obtained.");
    }
    /// 

    /// Add variables to the dynamic math formula. The variable should be properly declared.
    /// 
    /// Should be declared as "VariableName=VALUE" without spaces
    public void AddVariable(string variableDeclaration)
    {            
        if (!string.IsNullOrWhiteSpace(variableDeclaration))
        {
            var variable = variableDeclaration.ToLower().Split('=');    //Let's make sure the variable's name is LOWER case and then get its name/value
            string variableName = variable[0];
            double variableValue = 0;

            if (double.TryParse(variable[1], out variableValue))
                this.Variables.Add(variableName, variableValue);
            else
                throw new ArgumentException("Variable value is not a number");
        }
        else
        {
            //Could throw an exception... or just ignore as it not important...
        }
    }
}

以下是在WPF应用程序中使用上述类的示例(可以在任何C#应用程序中使用)

    private void btCalculate_Click(object sender, RoutedEventArgs e)
    {
        string expression = tboxExpression.Text;    //"cost * item / 100" (IT MUST BE SEPARATED WITH SPACES!)
        string variable1 = tboxVariable1.Text;      //"item=10"
        string variable2 = tboxVariable2.Text;      //"cost=2.5"

        DynamicFormula math = new DynamicFormula();
        math.Expression = expression;   //Let's define the expression
        math.AddVariable(variable1);    //Let's add the first variable
        math.AddVariable(variable2);    //Let's add the second variable

        try
        {
            double result = math.CalculateResult(); //In this scenario the result is 0,25... cost * item / 100 = (2.5 * 10 / 100) = 0,25
            //Console.WriteLine("Success: " + result);
            tboxResult.Text = result.ToString();
        }
        catch(Exception ex)
        {
            //Console.WriteLine(ex.Message);
            tboxResult.Text = ex.Message;
        }
    }

2)如果您需要更强大的东西以及大多数现实生活中的情况,您应该明确地查看FLEE:http://flee.codeplex.com/wikipage？title = Example &referringTitle = Home

这是专门为此制作的库,它支持多个公式!可能需要一些时间来查看一些示例并了解它是如何工作的,但它应该在没有太多工作的情况下完成工作.

希望能帮助到你,

LuísHenriqueGoll.