C#通过Expression实现字符串转表达式自定义计算体积参数

Expression实现字符串转表达式自定义计算体积参数

这篇文章是为了解决我工作中的一个需求而写，希望能帮到有需要的人

需求的这样的:
业务想让用户输入任意表达式进行计算假如成立则允许操作

表达式组成：
常量与特殊变量进行任意加减乘除有特殊值比较大小

表达式实例:

L+2*W<200
H>50
L/W+H*20-10>=100

调用方法

ExpressionVolume expressionVolume = new ExpressionVolume();//计算表达式的值Console.WriteLine(expressionVolume.InvokeOperator("L+10+2*W/10+H+200-800/20+L+W>=200", new ExpressionVolume.VolumeClass(10, 50, 100)));Console.WriteLine(expressionVolume.InvokeOperator("L+10+2*W/10+H+200-800/4+L+H/W>=200", new ExpressionVolume.VolumeClass(1, 1, 1)));Console.WriteLine((decimal)10 + (decimal)10 + (decimal)2 * (decimal)50 / (decimal)10 + (decimal)100 + (decimal)200 - (decimal)800 / (decimal)20 + (decimal)10 + (decimal)50);Console.WriteLine((decimal)1 + (decimal)10 + (decimal)2 * (decimal)1 / (decimal)10 + (decimal)1 + (decimal)200 - (decimal)800 / (decimal)4 + (decimal)1 + (decimal)1 / (decimal)1);//比较表达式是否成立Console.WriteLine(expressionVolume.InvokeEqual("L+10+2*W/10+H+200-800/20+L+W<200", new ExpressionVolume.VolumeClass(10, 50, 100)));Console.WriteLine(expressionVolume.InvokeEqual("L+10+2*W/10+H+200-800/4+L+H/W<200", new ExpressionVolume.VolumeClass(1, 1, 1)));//验证表达式是否成立(!=-1表示成立)Console.WriteLine(expressionVolume.Verification("L+10+2*W/10+H+200-800/20+L+W<200")); Console.WriteLine(expressionVolume.Verification("W+10+2*W/10+H+200-800/20+W+W<200"));Console.WriteLine(expressionVolume.Verification("L+2+2*-W/10+H+200-800/20+L+W<=200"));Console.WriteLine(expressionVolume.Verification("-L+33+2/*W/10+H+200-800/20+L+W>=200"));Console.WriteLine(expressionVolume.Verification("L+10-+2*W/10+H+200-800/20+L+W"));Console.WriteLine(expressionVolume.Verification("L++10+2*W/10+H+200-800/20+L+W"));expressionVolume.Verification("L+10+2*W/10+HL+200-800/20+L+W<200");

代码实现

/// <summary>/// 计算体积参数/// </summary>public class ExpressionVolume{#region 私有类/// <summary>/// 体积参数类/// </summary>public class VolumeClass{/// <summary>/// 不可以去掉/// Expression合成方法时需要支持无参实例化/// </summary>public VolumeClass(){}/// <summary>/// 实例化/// </summary>/// <param name="Long">长</param>/// <param name="Width">宽</param>/// <param name="Height">高</param>public VolumeClass(decimal? Long, decimal? Width, decimal? Height, decimal? Wt_Weight = null){this.L = Long ?? 0;this.W = Width ?? 0;this.H = Height ?? 0;this.Wt_Weight = Wt_Weight ?? 0;}/// <summary>/// 长/// </summary>/// <remarks>/// 不能随意改变字段名/// Expression合成方法时需要/// </remarks>public decimal L { get; set; }/// <summary>/// 宽/// </summary>/// <remarks>/// 不能随意改变字段名/// Expression合成方法时需要/// </remarks>public decimal W { get; set; }/// <summary>/// 高/// </summary>/// <remarks>/// 不能随意改变字段名/// Expression合成方法时需要/// </remarks>public decimal H { get; set; }/// <summary>/// 重量/// </summary>public decimal Wt_Weight { get; set; }}#endregion/// <summary>/// 线程锁，防止缓存键值对时异常/// </summary>private readonly static object Lock = new object { };/// <summary>/// 缓存表达式(比较)/// </summary>private readonly static Dictionary<string, Func<VolumeClass, bool>> DicEqual = new Dictionary<string, Func<VolumeClass, bool>>();/// <summary>/// 比较表达式是否成立/// </summary>/// <param name="expressionString">表达式</param>/// <param name="volume">体积参数</param>/// <returns></returns>public bool InvokeEqual(string expressionString, VolumeClass volume){if (DicEqual.ContainsKey(expressionString)){return DicEqual[expressionString].Invoke(volume);}var strs = expressionString.Split('>', '<');if (strs.Length != 2){DicEqual.Add(expressionString, t => false);return false;}//定义体积参数ParameterExpression parameterExpression = Expression.Parameter(typeof(VolumeClass), "volume");Expression expression = GetExpression(strs[0], parameterExpression);//是否大于bool IsGreaterThan = expressionString.Contains('>');//是否允许相等bool IsEqual = strs[1].StartsWith("=");strs[1] = strs[1].TrimStart('=');decimal Equal = decimal.Parse(strs[1]);if (IsGreaterThan){if (IsEqual){expression = Expression.GreaterThanOrEqual(expression, Expression.Constant(Equal, typeof(decimal)));}else{expression = Expression.GreaterThan(expression, Expression.Constant(Equal, typeof(decimal)));}}else{if (IsEqual){expression = Expression.LessThanOrEqual(expression, Expression.Constant(Equal, typeof(decimal)));}else{expression = Expression.LessThan(expression, Expression.Constant(Equal, typeof(decimal)));}}//获得Lambda表达式Expression<Func<VolumeClass, bool>> Lambda = Expression.Lambda<Func<VolumeClass, bool>>(expression, parameterExpression);//生成对应的委托var func = Lambda.Compile();//防止并发导致异常if (!DicEqual.ContainsKey(expressionString)){lock (Lock){if (!DicEqual.ContainsKey(expressionString)){//缓存委托DicEqual.Add(expressionString, func);}}}return func.Invoke(volume);}/// <summary>/// 缓存表达式(计算值)/// </summary>private readonly static Dictionary<string, Func<VolumeClass, decimal>> DicOperator = new Dictionary<string, Func<VolumeClass, decimal>>();/// <summary>/// 得到表达式左侧的值/// </summary>/// <param name="expressionString">表达式</param>/// <param name="volume">体积参数</param>/// <returns></returns>public decimal InvokeOperator(string expressionString, VolumeClass volume){if (DicOperator.ContainsKey(expressionString)){return DicOperator[expressionString].Invoke(volume);}var strs = expressionString.Split('>', '<');if (strs.Length != 2){DicOperator.Add(expressionString, t => -1);return -1;}//定义体积参数ParameterExpression parameterExpression = Expression.Parameter(typeof(VolumeClass), "volume");System.Linq.Expressions.Expression expression = GetExpression(strs[0], parameterExpression);//获得Lambda表达式Expression<Func<VolumeClass, decimal>> Lambda = Expression.Lambda<Func<VolumeClass, decimal>>(expression, parameterExpression);//生成对应的委托var func = Lambda.Compile();//防止并发导致异常if (!DicOperator.ContainsKey(expressionString)){lock (Lock){if (!DicOperator.ContainsKey(expressionString)){//缓存委托DicOperator.Add(expressionString, func);}}}return func.Invoke(volume);}/// <summary>/// 验证表达式/// </summary>/// <param name="expressionString">表达式</param>/// <returns></returns>public decimal Verification(string expressionString){var strs = expressionString.Split('>', '<');if (strs.Length != 2){DicOperator.Add(expressionString, t => -1);return -1;}if (string.IsNullOrEmpty(strs[1])){return -1;}//定义体积参数ParameterExpression parameterExpression = Expression.Parameter(typeof(VolumeClass), "volume");System.Linq.Expressions.Expression expression = GetExpression(strs[0], parameterExpression);//获得Lambda表达式Expression<Func<VolumeClass, decimal>> Lambda = Expression.Lambda<Func<VolumeClass, decimal>>(expression, parameterExpression);//生成对应的委托var func = Lambda.Compile();return func.Invoke(new VolumeClass(1, 1, 1));}#region 私有方法/// <summary>/// 生成公共表达式/// </summary>/// <param name="str"></param>/// <param name="parameterExpression">定义体积参数</param>/// <returns></returns>private System.Linq.Expressions.Expression GetExpression(string str, ParameterExpression parameterExpression){if (str.StartsWith("+") || str.StartsWith("-") || str.StartsWith("*") || str.StartsWith("/")){throw new Exception("表达式不能已符号开头");}Expression expression = null;foreach (var Add in str.Split('+')){if (Add.Contains('-')){//假如是第一次进入则表示还是+bool IsFirst = true;foreach (var Subtract in Add.Split('-')){Expression _expression = null;if (Subtract.Contains('*')){_expression = MultiplyAction(Subtract, parameterExpression);}else if (Subtract.Contains('/')){_expression = DivideAction(Subtract, parameterExpression);}else{_expression = GetPropertyOrConstant(Subtract, parameterExpression);}if (IsFirst){expression = expression == null ? _expression : Expression.Add(expression, _expression);}else{//不是第一次进入不可能是nullexpression = Expression.Subtract(expression, _expression);}IsFirst = false;}}else if (Add.Contains('*')){Expression _expression = MultiplyAction(Add, parameterExpression);expression = expression == null ? _expression : Expression.Add(expression, _expression);}else if (Add.Contains('/')){Expression _expression = DivideAction(Add, parameterExpression);expression = expression == null ? _expression : Expression.Add(expression, _expression);}else{//拼接+Expression _expression = GetPropertyOrConstant(Add, parameterExpression);expression = expression == null ? _expression : Expression.Add(expression, _expression);}}return expression;}/// <summary>/// 乘/// </summary>/// <param name="str"></param>private System.Linq.Expressions.Expression MultiplyAction(string str, ParameterExpression parameterExpression){List<Expression> list = new List<Expression>();foreach (var Multiply in str.Split('*')){list.Add(Multiply.Contains('/') ? DivideAction(Multiply, parameterExpression) : GetPropertyOrConstant(Multiply, parameterExpression));}Expression MultiplyExpression = list[0];for (int i = 1; i < list.Count; i++){MultiplyExpression = Expression.Multiply(MultiplyExpression, list[i]);}return MultiplyExpression;}/// <summary>/// 除/// </summary>/// <param name="str"></param>private System.Linq.Expressions.Expression DivideAction(string str, ParameterExpression parameterExpression){string[] strs = str.Split('/');return Expression.Divide(GetPropertyOrConstant(strs[0], parameterExpression), GetPropertyOrConstant(strs[1], parameterExpression));}/// <summary>/// 获取属性或常量/// </summary>/// <param name="value">字符串</param>/// <param name="parameterExpression">变量参数</param>/// <returns></returns>private System.Linq.Expressions.Expression GetPropertyOrConstant(string value, ParameterExpression parameterExpression){if (string.IsNullOrEmpty(value)){throw new Exception("符号不能相连");}Expression expression = null;if (value == "L" || value == "W" || value == "H"){//读取变量的属性expression = Expression.Property(parameterExpression, value);}else{try{expression = Expression.Constant(decimal.Parse(value), typeof(decimal));}catch (Exception){throw new Exception("长宽高不能相连");}}return expression;}#endregion}

实体类赋值(与本文章无关内容放到这边方便复制)

/// <summary>/// 不支持DataRow  泛型缓存/// </summary>/// <typeparam name="Tout">返回类型</typeparam>/// <typeparam name="Tin">接受类型</typeparam>public class ModelCopy<Tin, Tout>{private static Func<Tin, Tout> func { get; set; }//静态缓存字段/// <summary>/// 赋值/// </summary>/// <param name="model"></param>/// <returns></returns>public static Tout Invoke(Tin model)//公共方法，返回Map到的对象实例{#region 为Func赋值if (func == null){Type inType = typeof(Tin);Type outType = typeof(Tout);ParameterExpression parameterExpression = Expression.Parameter(inType, "tIn");//准备一个参数表达式List<MemberBinding> memberBindings = new List<MemberBinding>();//准备属性绑定的集合foreach (var item in outType.GetProperties())//遍历所有的属性{PropertyInfo propertyInfo = inType.GetProperty(item.Name);//获取到传入实例中的属性if (propertyInfo == null)continue;MemberExpression memberExpression = Expression.Property(parameterExpression, propertyInfo);//准备一个成员的表达式MemberBinding memberBinding = Expression.Bind(item, memberExpression);//绑定memberBindings.Add(memberBinding);//添加到列表}//字段//foreach (var item in outType.GetFields())//{//    FieldInfo fieldInfo = inType.GetField(item.Name);//    if (fieldInfo == null)//        continue;//    MemberExpression memberExpression = Expression.Field(parameterExpression, fieldInfo);//    MemberBinding memberBinding = Expression.Bind(item, memberExpression);//    memberBindings.Add(memberBinding);//}MemberInitExpression memberInitExpression = Expression.MemberInit(Expression.New(outType), memberBindings.ToArray());Expression<Func<Tin, Tout>> lambdaExpression = Expression.Lambda<Func<Tin, Tout>>(memberInitExpression, new ParameterExpression[] { parameterExpression });func = lambdaExpression.Compile();//表达式编译为委托}#endregionreturn func.Invoke(model);}}

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