计算字符串得出结果
需求：
在C#中对一个字符串进行计算得出结果。
例如：“1+2+66+33”
字符串中的数字可以变化，累加（这里偷懒了限定成累加）的次数可以变化。
思路/解决方案：
1. 用JavaScript中的Eval把字符串转成对象进行计算
用Com控件计算方法，引入MSScriptControl.ScriptControlClass
2.用DataTable().Compute计算方法
3.把字符串表达式作为一个sql发到数据库计算后结果再回传到程序
4.分解字符串用 lambda表达式树动态创建一个（累加）表达式
说明：
我做了一个随机数，然后将每次随机出来的数字拼接成一个字符串展示出来。
再来解析这个字符串得出计算结果。
需要注意表达式树的方式，你的参数列表paramslist必须是 object[] 这个类型，我之前用的int[] 也可以编译但是在运行的时候会报错，你的paramenterArray应当就是构成binaryexpression的那些ParameterExpression。
如果你的业务里面要用到更加复杂运算，你需要亲自来尝试。
欢迎吐槽。
代码：
using System; using System.Collections.Generic; using System.Text; using System.Linq.Expressions; using System.Reflection; namespace guess { class Program { static void Main(string[] args) { try { Console.WriteLine(SetRandomVariable(GetTemplate())); } catch (Exception ex) { Console.WriteLine(ex.Message); } #if DEBUG Console.Read(); #endif } private static string GetTemplate() { StringBuilder stb = new StringBuilder(); stb.AppendLine("Bangladesh - OneERP {0}hr"); stb.AppendLine("CN - OneERP {1}hr"); stb.AppendLine("Global - OneERP {2}hr"); stb.AppendLine("FE - OneERP {3}hr"); stb.AppendLine("UK - OneERP {4}hr"); stb.AppendLine("Turkey - OneERP {5}hr"); stb.AppendLine("Vietnam – OneERP {6}hr"); stb.AppendLine("Singapore - OneERP {7}hr"); stb.AppendLine("CN - HZ {8}hr"); stb.AppendLine("Romania - OneERP {9}hr"); stb.AppendLine("Thailand - OneERP {10}hr"); stb.AppendLine("ZheJiang - OneERP {11}hr"); stb.AppendLine("Global - OneERP SSO {12}hr"); return stb.ToString(); } private static string SetRandomVariable(string getTemplate) { int count = getTemplate.Split('\n').Length - 1; Random randomVariable = new Random(DateTime.Now.Millisecond); int max = 40; StringBuilder formula = new StringBuilder(); object[] paramslist = new object[count]; for (int i = 0; i < paramslist.Length; i++) { if (i == paramslist.Length - 1) { paramslist[i] = max; formula.Append(max); } else { paramslist[i] = available(ref max, ref formula); } } //Com控件计算方法 需要目标平台X86 D找到引用的dll——属性——嵌入互操作类型——false MSScriptControl.ScriptControl sc = new MSScriptControl.ScriptControlClass(); sc.Language = "JavaScript"; Console.WriteLine("{0}={1}", formula.ToString(), sc.Eval(formula.ToString()).ToString()); //DataTable().Compute计算方法 Console.WriteLine("{0}={1}", formula.ToString(), new System.Data.DataTable().Compute(formula.ToString(), "").ToString()); //另外有一种思路，把表达式作为一个sql发到数据库计算后结果再回传到程序。 //lambda表达式树动态创建一个累加的表达式 需要.net FrameWork 4.5 BinaryExpression binaryexpression = addExpression(count,null); Console.WriteLine(binaryexpression); LambdaExpression lambdaExpr = Expression.Lambda(binaryexpression, paramenterArray); Delegate de = lambdaExpr.Compile(); // MethodInfo method = de.Method; Console.WriteLine(de.DynamicInvoke(paramslist)); return string.Format(getTemplate, paramslist); } private static int available(ref int max, ref StringBuilder formula) { int temp = 0; if (max > 0) { Random randomVariable = new Random(); if (max == 1) { temp = randomVariable.Next(0, max + 1); } else { temp = randomVariable.Next(0, max); } max = max - temp; } formula.AppendFormat("{0}+", temp); return temp; } static List<ParameterExpression> paramenterArray=new List<ParameterExpression>() ; /// <summary> /// /// </summary> /// <param name="lenght">累加次数</param> /// <param name="resultLeft">默认累加表达式</param> /// <returns></returns> private static BinaryExpression addExpression(int lenght, BinaryExpression resultLeft) { try { ParameterExpression left, right; left = Expression.Parameter(typeof(int), string.Format("left{0}", lenght) ); right = Expression.Parameter(typeof(int), string.Format("right{0}", (lenght - 1)) ); BinaryExpression result = Expression.Add(left, right); if (lenght > 2) { paramenterArray.Add(left); paramenterArray.Add(right); if (resultLeft != null) result = Expression.Add(resultLeft, addExpression(lenght - 2, result)); else result = addExpression(lenght - 2, result); } if (lenght == 2) { paramenterArray.Add(left); paramenterArray.Add(right); if (resultLeft != null) result = Expression.Add(resultLeft, result); else { //ignore; } } if (lenght == 1) { if (resultLeft != null) { ParameterExpression rExpression = Expression.Parameter(typeof(int), string.Format("right{0}", lenght )); paramenterArray.Add(rExpression); result = Expression.Add(resultLeft, rExpression); } else { throw (new Exception("当lenght等于1时，resultLeft参数不能为空")); } } return result; } catch ( Exception ex) { #if DEBUG Console.WriteLine(ex.StackTrace.ToString()); #endif throw (ex); } } } }
收录羽铉君的四则混合运算写法。Pop(), Push(opt) ,Peek()的范例。
public class Calculator { public Calculator() { _OptStack = new Stack<char>(); _SuffixStack = new Stack<float>(); } private Stack<char> _OptStack; private Stack<float> _SuffixStack; public float Calculate(string expression) { string lastNum = string.Empty; for (int i = 0; i < expression.Length; i++) { if (char.IsNumber(expression[i]) || expression[i].Equals('.')) { lastNum += expression[i]; } else { if (lastNum != string.Empty) { Merger(float.Parse(lastNum)); lastNum = string.Empty; } AddOpt(expression[i]); } } if (lastNum != string.Empty) { Merger(float.Parse(lastNum)); } while (_OptStack.Count > 0) { Merger(_OptStack.Pop()); } return _SuffixStack.Pop(); } private void AddOpt(char opt) { if (_OptStack.Count == 0) { _OptStack.Push(opt); return; } if (opt.Equals(')')) { while (!_OptStack.Peek().Equals('(')) { Merger(_OptStack.Pop()); } _OptStack.Pop(); return; } char tempOpt = _OptStack.Peek(); if ((opt.Equals('-') || opt.Equals('+')) && (tempOpt.Equals('*') || tempOpt.Equals('/'))) { while (_OptStack.Count > 0) { Merger(_OptStack.Pop()); } } _OptStack.Push(opt); } private void Merger(float exp) { _SuffixStack.Push(exp); } private void Merger(char exp) { float num1 = _SuffixStack.Pop(); float num2 = _SuffixStack.Pop(); float result = 0; switch (exp) { case '+': result = num2 + num1; break; case '-': result = num2 - num1; break; case '*': result = num2 * num1; break; case '/': result = num2 / num1; break; } _SuffixStack.Push(result); } } //调用写法 //string calc = "89+(126/2)*3-6/3+(96+3-8/2)";// 随便写四则运算 //Calculator calculator = new Calculator(); //MessageBox.Show(calculator.Calculate(calc).ToString()); // 结果
