今天就跟大家聊聊有关如何在C#中使用RulesEngine规则引擎，可能很多人都不太了解，为了让大家更加了解，小编给大家总结了以下内容，希望大家根据这篇文章可以有所收获。
简介
RulesEngine是微软推出的规则引擎，规则引擎在很多企业开发中有所应用，是处理经常变动需求的一种优雅的方法。个人任务，规则引擎适用于以下的一些场景：
输入输出类型数量比较固定，但是执行逻辑经常变化；
switch条件经常变化，复杂switch语句的替代；
会变动的，具有多种条件或者规则的业务逻辑；
规则自由度不要求特别高的场景。（这种情况建议使用脚本引擎）
RulesEngine的规则使用JSON进行存储，通过lambda表达式方式表述规则（Rules）。
安装很方便，直接使用nuget进行安装：
install-pacakge RulesEngine
需要有Rules，有WorkflowName，然后还有一些属性。
[
{
"WorkflowName": "Discount",
"Rules": [
{
"RuleName": "GiveDiscount10",
"SuccessEvent": "10",
"ErrorMessage": "One or more adjust rules failed.",
"ErrorType": "Error",
"RuleExpressionType": "LambdaExpression",
"Expression": "input1.country == \"india\" AND input1.loyalityFactor <= 2 AND input1.totalPurchasesToDate >= 5000 AND input2.totalOrders > 2 AND input3.noOfVisitsPerMonth > 2"
}
]
}
]除了标准的RuleExpressionType，还可以通过定义Rules嵌套多个条件，下面是Or逻辑。
{
"RuleName": "GiveDiscount30NestedOrExample",
"SuccessEvent": "30",
"ErrorMessage": "One or more adjust rules failed.",
"ErrorType": "Error",
"Operator": "OrElse",
"Rules":[
{
"RuleName": "IsLoyalAndHasGoodSpend",
"ErrorMessage": "One or more adjust rules failed.",
"ErrorType": "Error",
"RuleExpressionType": "LambdaExpression",
"Expression": "input1.loyalityFactor > 3 AND input1.totalPurchasesToDate >= 50000 AND input1.totalPurchasesToDate <= 100000"
},
{
"RuleName": "OrHasHighNumberOfTotalOrders",
"ErrorMessage": "One or more adjust rules failed.",
"ErrorType": "Error",
"RuleExpressionType": "LambdaExpression",
"Expression": "input2.totalOrders > 15"
}
]
}可以从官方的代码库中下载示例，定义了上述规则，就可以直接开始用了。示例描述了这么一个应用场景：
根据不同的客户属性，提供不同的折扣。由于销售的情况变化较快，提供折扣的规则也需要经常变动。因此比较适用于规则引擎。
public void Run()
{
Console.WriteLine($"Running {nameof(BasicDemo)}....");
//创建输入
var basicInfo = "{\"name\": \"hello\",\"email\": \"abcy@xyz.com\",\"creditHistory\": \"good\",\"country\": \"canada\",\"loyalityFactor\": 3,\"totalPurchasesToDate\": 10000}";
var orderInfo = "{\"totalOrders\": 5,\"recurringItems\": 2}";
var telemetryInfo = "{\"noOfVisitsPerMonth\": 10,\"percentageOfBuyingToVisit\": 15}";
var converter = new ExpandoObjectConverter();
dynamic input1 = JsonConvert.DeserializeObject(basicInfo, converter);
dynamic input2 = JsonConvert.DeserializeObject(orderInfo, converter);
dynamic input3 = JsonConvert.DeserializeObject(telemetryInfo, converter);
var inputs = new dynamic[]
{
input1,
input2,
input3
};
//加载规则
var files = Directory.GetFiles(Directory.GetCurrentDirectory(), "Discount.json", SearchOption.AllDirectories);
if (files == null || files.Length == 0)
throw new Exception("Rules not found.");
var fileData = File.ReadAllText(files[0]);
var workflowRules = JsonConvert.DeserializeObject>(fileData);
//初始化规则引擎
var bre = new RulesEngine.RulesEngine(workflowRules.ToArray(), null);
string discountOffered = "No discount offered.";
//执行规则
List resultList = bre.ExecuteAllRulesAsync("Discount", inputs).Result;
//处理结果
resultList.OnSuccess((eventName) => {
discountOffered = $"Discount offered is {eventName} % over MRP.";
});
resultList.OnFail(() => {
discountOffered = "The user is not eligible for any discount.";
});
Console.WriteLine(discountOffered);
} 输入一般来说是IEnumerable
var nestedInput = new {
SimpleProp = "simpleProp",
NestedProp = new {
SimpleProp = "nestedSimpleProp",
ListProp = new List
{
new ListItem
{
Id = 1,
Value = "first"
},
new ListItem
{
Id = 2,
Value = "second"
}
}
}
}; 和脚本引擎一样，默认规则引擎只能访问System的命名空间。如果需要使用到稍微复杂一些的类型，可以自己定义类型或者函数。比如定义一个这样的函数：
public static class Utils
{
public static bool CheckContains(string check, string valList)
{
if (String.IsNullOrEmpty(check) || String.IsNullOrEmpty(valList))
return false;
var list = valList.Split(',').ToList();
return list.Contains(check);
}
}需要使用的时候，先将类传递给RulesEngine：
var reSettingsWithCustomTypes = new ReSettings { CustomTypes = new Type[] { typeof(Utils) } };
var engine = new RulesEngine.RulesEngine(workflowRules.ToArray(), null, reSettingsWithCustomTypes);然后就可以直接在表达式中使用了。
"Expression": "Utils.CheckContains(input1.country, \"india,usa,canada,France\") == true"
默认情况下，规则的输入使用的是类似input1 input2这样的形式，如果想直观一点，可以使用RuleParameter来进行封装具体的参数类型。
RuleParameter ruleParameter = new RuleParameter("NIP", nestedInput);
var resultList = bre.ExecuteAllRulesAsync(workflow.WorkflowName, ruleParameter).Result;如果表达式比较复杂的情况下，可以使用本地变量来进行分段处理，这对调试来说会比较方便。
本地变量的关键字为localParams，可以将中间的内容简单理解成var name = expression
{
"name": "allow_access_if_all_mandatory_trainings_are_done_or_access_isSecure",
"errorMessage": "Please complete all your training(s) to get access to this content or access it from a secure domain/location.",
"errorType": "Error",
"localParams": [
{
"name": "completedSecurityTrainings",
"expression": "MasterSecurityComplainceTrainings.Where(Status.Equals(\"Completed\", StringComparison.InvariantCultureIgnoreCase))"
},
{
"name": "completedProjectTrainings",
"expression": "MasterProjectComplainceTrainings.Where(Status.Equals(\"Completed\", StringComparison.InvariantCultureIgnoreCase))"
},
{
"name": "isRequestAccessSecured",
"expression": "UserRequestDetails.Location.Country == \"India\" ? ((UserRequestDetails.Location.City == \"Bangalore\" && UserRequestDetails.Domain=\"xxxx\")? true : false):false"
}
],
"expression": "(completedSecurityTrainings.Any() && completedProjectTrainings.Any()) || isRequestAccessSecured "
}看完上述内容，你们对如何在C#中使用RulesEngine规则引擎有进一步的了解吗？如果还想了解更多知识或者相关内容，请关注创新互联行业资讯频道，感谢大家的支持。
