[.Net] .NET RulesEngine（规则引擎）的使用详解

• RulesEngine 概述
  
• 如何使用
  
• 表达树内使用扩展方法
  
• 多对象组合条件
  
• 如何实现的？
  
• 成功失败事件
  
• 总结
  

dotnet add package RulesEngine

//反序列化Json格式规则字符串
var workflowRules = JsonConvert.DeserializeObject<List<WorkflowRules>>(rulesStr);
 var rulesEngine = new RulesEngine.RulesEngine(workflowRules.ToArray());

//定义规则
      var rulesStr = @"[{
          ""WorkflowName"": ""UserInputWorkflow"",
          ""Rules"": [
            {
            ""RuleName"": ""CheckAge"",
            ""ErrorMessage"": ""年龄必须大于18岁."",
            ""ErrorType"": ""Error"",
            ""RuleExpressionType"": ""LambdaExpression"",
            ""Expression"": ""Age > 18""
            },
             {
            ""RuleName"": ""CheckIDNoIsEmpty"",
            ""ErrorMessage"": ""身份证号不可以为空."",
             ""ErrorType"": ""Error"",
            ""RuleExpressionType"": ""LambdaExpression"",
            ""Expression"": ""IdNo != null""
            }
          ]
          }] ";

public class UserInput
    {
      public string IdNo { get; set; }
      public int Age { get; set; }
    }

static async Task Main(string[] args)
    {
      var userInput = new UserInput
      {
        IdNo = null,
        Age = 18
      };
      //反序列化Json格式规则字符串
      var workflowRules = JsonConvert.DeserializeObject<List<WorkflowRules>>(rulesStr);
      
      var rulesEngine = new RulesEngine.RulesEngine(workflowRules.ToArray());
      List<RuleResultTree> resultList = await rulesEngine.ExecuteAllRulesAsync("UserInputWorkflow", userInput);
      foreach (var item in resultList)
      {         
         Console.WriteLine("验证成功：{0}，消息：{1}",item.IsSuccess,item.ExceptionMessage);
      }
      Console.ReadLine();
    }

　　验证成功：False，消息：年龄必须大于18岁.
验证成功：False，消息：身份证号不可以为空.

{ "Rule":{ "RuleName":"CheckNestedSimpleProp","Properties":null,"Operator":null,"ErrorMessage":"年龄必须大于18岁.",
        "ErrorType":"Error","RuleExpressionType":"LambdaExpression","WorkflowRulesToInject":null,"Rules":null,"LocalParams":null,"Expression":"Age > 18","Actions":null,"SuccessEvent":null},"IsSuccess":false,"ChildResults":null,"Inputs":{ "input1":{ "IdNo":null,"Age":18} },
        "ActionResult":{ "Output":null,"Exception":null},"ExceptionMessage":"年龄必须大于18岁.","RuleEvaluatedParams":[]}

private static readonly ReSettings reSettings = new ReSettings
    {
      CustomTypes = new[] { typeof(IdCardUtil) }
    };

var rulesEngine = new RulesEngine.RulesEngine(workflowRules.ToArray(), null, reSettings: reSettings);

var rulesStr = @"[{
          ""WorkflowName"": ""UserInputWorkflow"",
          ""Rules"": [
            {
            ""RuleName"": ""CheckNestedSimpleProp"",
            ""ErrorMessage"": ""年龄必须小于18岁."",
            ""ErrorType"": ""Error"",
            ""RuleExpressionType"": ""LambdaExpression"",
            ""Expression"": ""IdNo.GetAgeByIdCard() < 18""
            },
             {
            ""RuleName"": ""CheckNestedSimpleProp1"",
            ""ErrorMessage"": ""身份证号不可以为空."",
             ""ErrorType"": ""Error"",
            ""RuleExpressionType"": ""LambdaExpression"",
            ""Expression"": ""IdNo != null""
            }
          ]
          }] ";

var rulesStr = @"[{
          ""WorkflowName"": ""UserInputWorkflow"",
          ""Rules"": [
            {
            ""RuleName"": ""CheckNestedSimpleProp"",
            ""ErrorMessage"": ""Value值不是second."",
            ""ErrorType"": ""Error"",
            ""RuleExpressionType"": ""LambdaExpression"",
            ""Expression"": ""user.UserId==1 && items[0].Value==second""
            }
          ]
          }] ";

      var userInput = new UserInput
      {
        UserId = 1,
        IdNo = "11010519491230002X",
        Age = 18
      };
      var input = new
      {
        user = userInput,
        items = new List<ListItem>()
        {
          new ListItem{ Id=1,Value="first"},
          new ListItem{ Id=2,Value="second"}
        }
      };

　　验证成功：False，消息：Value值不是second.

var items = input.items.AsQueryable().Where("Id == 1").ToList();

foreach (var item in items)
{
  Console.WriteLine($"Id：{item.Id},Value: {item.Value}");
}

　　Id：1,Value: first

Expression<Func<ListItem, bool>> predicate = x => x.Id == 1;
      //输入条件如下
      var inputItem = new ListItem
      {
        Id = 1,
        Value = "second"
      };
      if (inputItem.Id !=null)
      {
        predicate = predicate.And(x=>x.Id==inputItem.Id);
      }
      if (inputItem.Id != null)
      {
        predicate = predicate.And(x => x.Value == inputItem.Value);
      }
      
  public static class PredicateBuilder
  {
    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1,
                              Expression<Func<T, bool>> expr2)
    {
      var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
      return Expression.Lambda<Func<T, bool>>
          (Expression.And(expr1.Body, invokedExpr), expr1.Parameters);
    }
  }

var items = input.items.AsQueryable().Where("Id ==@0  && Value==@1",inputItem.Id,inputItem.Value).ToList();

var discountOffered = "";
      resultList.OnSuccess((eventName) =>
      {
        discountOffered = $"成功事件:{eventName}.";
      });

      resultList.OnFail(() =>
      {
        discountOffered = "失败事件.";
      });