基于领域驱动设计(DDD)超轻量级快速开发架构(二)动态linq查询的实现方式

-之动态查询,查询逻辑封装复用

基于领域驱动设计(DDD)超轻量级快速开发架构详细介绍请看

https://www.cnblogs.com/neozhu/p/13174234.html

需求

1. 配合EasyUI datagird filter实现多字段(任意字段)的筛选
2. 根据业务需求筛选特定的状态或条件,如:查看结案的订单,最近30天的订单,查看属于我的订单.等等,这些逻辑是固定也是可以被重用,但又不想每次写相同的条件,那么下面我会给我的解决方案.

需求1只是一个偷懒的实现方式,因为datagrid自带这个功能,但又不想根据具体的需求来画查询条件,如果需求必须要再datagrid上面做一块查询条件的输入那目前只能在前端自己手工添加,在组织后传入后台,暂时不在这里讨论

需求2可能不太好解释,看完代码就自然理解为什么要这么做了,这么做的好处有哪些

具体实现的方式

 默认情况下 datagrid 有几列就可以对这几列进行筛选,对于日期型的字段会采用between,选择2个时间之间进行筛选,数字类型会提供大于小于等符号选择,可以自行尝试,其原理是datagrid 会根据datagrid 头部输入的值生成一个Json字符串发送后台请求数据

JSON:格式

filterRules: [
{field:field,op:op,value:value},

{field:field,op:op,value:value},

] 

• 通常的做法是一个一个判断加条件

var filters = JsonConvert.DeserializeObject<IEnumerable<filterRule>>(filterRules); 
foreach (var rule in filters)
        {
          if (rule.field == "Id" && !string.IsNullOrEmpty(rule.value) && rule.value.IsInt())
          {
            var val = Convert.ToInt32(rule.value);
            switch (rule.op)
            {
              case "equal":
                this.And(x => x.Id == val);
                break;
              case "notequal":
                this.And(x => x.Id != val);
                break;
              case "less":
                this.And(x => x.Id < val);
                break;
              case "lessorequal":
                this.And(x => x.Id <= val);
                break;
              case "greater":
                this.And(x => x.Id > val);
                break;
              case "greaterorequal":
                this.And(x => x.Id >= val);
                break;
              default:
                this.And(x => x.Id == val);
                break;
            }
          }
          if (rule.field == "Name" && !string.IsNullOrEmpty(rule.value))
          {
            this.And(x => x.Name.Contains(rule.value));
          }
          if (rule.field == "Code" && !string.IsNullOrEmpty(rule.value))
          {
            this.And(x => x.Code.Contains(rule.value));
          }

          if (rule.field == "Address" && !string.IsNullOrEmpty(rule.value))
          {
            this.And(x => x.Address.Contains(rule.value));
          }

          if (rule.field == "Contect" && !string.IsNullOrEmpty(rule.value))
          {
            this.And(x => x.Contect.Contains(rule.value));
          }

          if (rule.field == "PhoneNumber" && !string.IsNullOrEmpty(rule.value))
          {
            this.And(x => x.PhoneNumber.Contains(rule.value));
          }

          if (rule.field == "RegisterDate" && !string.IsNullOrEmpty(rule.value))
          {
            if (rule.op == "between")
            {
              var datearray = rule.value.Split(new char[] { '-' });
              var start = Convert.ToDateTime(datearray[0]);
              var end = Convert.ToDateTime(datearray[1]);

              this.And(x => SqlFunctions.DateDiff("d", start, x.RegisterDate) >= 0);
              this.And(x => SqlFunctions.DateDiff("d", end, x.RegisterDate) <= 0);
            }
          }
          if (rule.field == "CreatedDate" && !string.IsNullOrEmpty(rule.value))
          {
            if (rule.op == "between")
            {
              var datearray = rule.value.Split(new char[] { '-' });
              var start = Convert.ToDateTime(datearray[0]);
              var end = Convert.ToDateTime(datearray[1]);

              this.And(x => SqlFunctions.DateDiff("d", start, x.CreatedDate) >= 0);
              this.And(x => SqlFunctions.DateDiff("d", end, x.CreatedDate) <= 0);
            }
          }


          if (rule.field == "CreatedBy" && !string.IsNullOrEmpty(rule.value))
          {
            this.And(x => x.CreatedBy.Contains(rule.value));
          }

         if (rule.field == "LastModifiedDate" && !string.IsNullOrEmpty(rule.value))
          {
            if (rule.op == "between")
            {
              var datearray = rule.value.Split(new char[] { '-' });
              var start = Convert.ToDateTime(datearray[0]);
              var end = Convert.ToDateTime(datearray[1]);

              this.And(x => SqlFunctions.DateDiff("d", start, x.LastModifiedDate) >= 0);
              this.And(x => SqlFunctions.DateDiff("d", end, x.LastModifiedDate) <= 0);
            }
          }

          if (rule.field == "LastModifiedBy" && !string.IsNullOrEmpty(rule.value))
          {
            this.And(x => x.LastModifiedBy.Contains(rule.value));
          }

        }

• 新的做法是动态根据field,op,value生成一个linq 表达式,不用再做繁琐的判断,这块代码也可以被其它项目使用,非常好用

namespace SmartAdmin
{
 
  public static class PredicateBuilder
  {

    public static Expression<Func<T, bool>> FromFilter<T>(string filtergroup) {
      Expression<Func<T, bool>> any = x => true;
      if (!string.IsNullOrEmpty(filtergroup))
      {
        var filters = JsonSerializer.Deserialize<filter[]>(filtergroup);

          foreach (var filter in filters)
          {
            if (Enum.TryParse(filter.op, out OperationExpression op) && !string.IsNullOrEmpty(filter.value))
            {
              var expression = GetCriteriaWhere<T>(filter.field, op, filter.value);
              any = any.And(expression);
            }
          }
      }

      return any;
    }

    #region -- Public methods --
    public static Expression<Func<T, bool>> GetCriteriaWhere<T>(Expression<Func<T, object>> e, OperationExpression selectedOperator, object fieldValue)
    {
      var name = GetOperand<T>(e);
      return GetCriteriaWhere<T>(name, selectedOperator, fieldValue);
    }

    public static Expression<Func<T, bool>> GetCriteriaWhere<T, T2>(Expression<Func<T, object>> e, OperationExpression selectedOperator, object fieldValue)
    {
      var name = GetOperand<T>(e);
      return GetCriteriaWhere<T, T2>(name, selectedOperator, fieldValue);
    }

    public static Expression<Func<T, bool>> GetCriteriaWhere<T>(string fieldName, OperationExpression selectedOperator, object fieldValue)
    {
      var props = TypeDescriptor.GetProperties(typeof(T));
      var prop = GetProperty(props, fieldName, true);
      var parameter = Expression.Parameter(typeof(T));
      var expressionParameter = GetMemberExpression<T>(parameter, fieldName);
      if (prop != null && fieldValue != null)
      {
       
        BinaryExpression body = null;
        switch (selectedOperator)
        {
          case OperationExpression.equal:
            body = Expression.Equal(expressionParameter, Expression.Constant(Convert.ChangeType(fieldValue, Nullable.GetUnderlyingType(prop.PropertyType)?? prop.PropertyType), prop.PropertyType));
            return Expression.Lambda<Func<T, bool>>(body, parameter);
          case OperationExpression.notequal:
            body = Expression.NotEqual(expressionParameter, Expression.Constant(Convert.ChangeType(fieldValue, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType), prop.PropertyType));
            return Expression.Lambda<Func<T, bool>>(body, parameter);
          case OperationExpression.less:
            body = Expression.LessThan(expressionParameter, Expression.Constant(Convert.ChangeType(fieldValue, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType), prop.PropertyType));
            return Expression.Lambda<Func<T, bool>>(body, parameter);
          case OperationExpression.lessorequal:
            body = Expression.LessThanOrEqual(expressionParameter, Expression.Constant(Convert.ChangeType(fieldValue, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType), prop.PropertyType));
            return Expression.Lambda<Func<T, bool>>(body, parameter);
          case OperationExpression.greater:
            body = Expression.GreaterThan(expressionParameter, Expression.Constant(Convert.ChangeType(fieldValue, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType), prop.PropertyType));
            return Expression.Lambda<Func<T, bool>>(body, parameter);
          case OperationExpression.greaterorequal:
            body = Expression.GreaterThanOrEqual(expressionParameter, Expression.Constant(Convert.ChangeType(fieldValue, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType), prop.PropertyType));
            return Expression.Lambda<Func<T, bool>>(body, parameter);
          case OperationExpression.contains:
            var contains = typeof(string).GetMethod("Contains", new[] { typeof(string) });
            var bodyLike = Expression.Call(expressionParameter, contains, Expression.Constant(Convert.ChangeType(fieldValue, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType), prop.PropertyType));
            return Expression.Lambda<Func<T, bool>>(bodyLike, parameter);
          case OperationExpression.endwith:
            var endswith = typeof(string).GetMethod("EndsWith",new[] { typeof(string) });
            var bodyendwith = Expression.Call(expressionParameter, endswith, Expression.Constant(Convert.ChangeType(fieldValue, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType), prop.PropertyType));
            return Expression.Lambda<Func<T, bool>>(bodyendwith, parameter);
          case OperationExpression.beginwith:
            var startswith = typeof(string).GetMethod("StartsWith", new[] { typeof(string) });
            var bodystartswith = Expression.Call(expressionParameter, startswith, Expression.Constant(Convert.ChangeType(fieldValue, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType), prop.PropertyType));
            return Expression.Lambda<Func<T, bool>>(bodystartswith, parameter);
          case OperationExpression.includes:
            return Includes<T>(fieldValue, parameter, expressionParameter, prop.PropertyType);
          case OperationExpression.between:
            return Between<T>(fieldValue, parameter, expressionParameter, prop.PropertyType);
          default:
            throw new Exception("Not implement Operation");
        }
      }
      else
      {
        Expression<Func<T, bool>> filter = x => true;
        return filter;
      }
    }

    public static Expression<Func<T, bool>> GetCriteriaWhere<T, T2>(string fieldName, OperationExpression selectedOperator, object fieldValue)
    {


      var props = TypeDescriptor.GetProperties(typeof(T));
      var prop = GetProperty(props, fieldName, true);

      var parameter = Expression.Parameter(typeof(T));
      var expressionParameter = GetMemberExpression<T>(parameter, fieldName);

      if (prop != null && fieldValue != null)
      {
        switch (selectedOperator)
        {
          case OperationExpression.any:
            return Any<T, T2>(fieldValue, parameter, expressionParameter);

          default:
            throw new Exception("Not implement Operation");
        }
      }
      else
      {
        Expression<Func<T, bool>> filter = x => true;
        return filter;
      }
    }



    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr, Expression<Func<T, bool>> or)
    {
      if (expr == null)
      {
        return or;
      }

      return Expression.Lambda<Func<T, bool>>(Expression.OrElse(new SwapVisitor(expr.Parameters[0], or.Parameters[0]).Visit(expr.Body), or.Body), or.Parameters);
    }

    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr, Expression<Func<T, bool>> and)
    {
      if (expr == null)
      {
        return and;
      }

      return Expression.Lambda<Func<T, bool>>(Expression.AndAlso(new SwapVisitor(expr.Parameters[0], and.Parameters[0]).Visit(expr.Body), and.Body), and.Parameters);
    }

    #endregion
    #region -- Private methods --

    private static string GetOperand<T>(Expression<Func<T, object>> exp)
    {
      if (!( exp.Body is MemberExpression body ))
      {
        var ubody = (UnaryExpression)exp.Body;
        body = ubody.Operand as MemberExpression;
      }

      var operand = body.ToString();

      return operand.Substring(2);

    }

    private static MemberExpression GetMemberExpression<T>(ParameterExpression parameter, string propName)
    {
      if (string.IsNullOrEmpty(propName))
      {
        return null;
      }

      var propertiesName = propName.Split('.');
      if (propertiesName.Count() == 2)
      {
        return Expression.Property(Expression.Property(parameter, propertiesName[0]), propertiesName[1]);
      }

      return Expression.Property(parameter, propName);
    }

    private static Expression<Func<T, bool>> Includes<T>(object fieldValue, ParameterExpression parameterExpression, MemberExpression memberExpression ,Type type)
    {
      var safetype= Nullable.GetUnderlyingType(type) ?? type;

      switch (safetype.Name.ToLower())
      {
        case  "string":
          var strlist = (IEnumerable<string>)fieldValue;
          if (strlist == null || strlist.Count() == 0)
          {
            return x => true;
          }
          var strmethod = typeof(List<string>).GetMethod("Contains", new Type[] { typeof(string) });
          var strcallexp = Expression.Call(Expression.Constant(strlist.ToList()), strmethod, memberExpression);
          return Expression.Lambda<Func<T, bool>>(strcallexp, parameterExpression);
        case "int32":
          var intlist = (IEnumerable<int>)fieldValue;
          if (intlist == null || intlist.Count() == 0)
          {
            return x => true;
          }
          var intmethod = typeof(List<int>).GetMethod("Contains", new Type[] { typeof(int) });
          var intcallexp = Expression.Call(Expression.Constant(intlist.ToList()), intmethod, memberExpression);
          return Expression.Lambda<Func<T, bool>>(intcallexp, parameterExpression);
        case "float":
          var floatlist = (IEnumerable<float>)fieldValue;
          if (floatlist == null || floatlist.Count() == 0)
          {
            return x => true;
          }
          var floatmethod = typeof(List<int>).GetMethod("Contains", new Type[] { typeof(int) });
          var floatcallexp = Expression.Call(Expression.Constant(floatlist.ToList()), floatmethod, memberExpression);
          return Expression.Lambda<Func<T, bool>>(floatcallexp, parameterExpression);
        default:
          return x => true;
      }
      
    }
    private static Expression<Func<T, bool>> Between<T>(object fieldValue, ParameterExpression parameterExpression, MemberExpression memberExpression, Type type)
    {
      
      var safetype = Nullable.GetUnderlyingType(type) ?? type;
      switch (safetype.Name.ToLower())
      {
        case "datetime":
          var datearray = ( (string)fieldValue ).Split(new char[] { '-' }, StringSplitOptions.RemoveEmptyEntries);
          var start = Convert.ToDateTime(datearray[0] + " 00:00:00", CultureInfo.CurrentCulture);
          var end = Convert.ToDateTime(datearray[1] + " 23:59:59", CultureInfo.CurrentCulture);
          var greater = Expression.GreaterThan(memberExpression, Expression.Constant(start, type));
          var less = Expression.LessThan(memberExpression, Expression.Constant(end, type));
          return Expression.Lambda<Func<T, bool>>(greater, parameterExpression)
            .And(Expression.Lambda<Func<T, bool>>(less, parameterExpression));
        case "int":
        case "int32":
          var intarray = ( (string)fieldValue ).Split(new char[] { '-' }, StringSplitOptions.RemoveEmptyEntries);
          var min = Convert.ToInt32(intarray[0] , CultureInfo.CurrentCulture);
          var max = Convert.ToInt32(intarray[1], CultureInfo.CurrentCulture);
          var maxthen = Expression.GreaterThan(memberExpression, Expression.Constant(min, type));
          var minthen = Expression.LessThan(memberExpression, Expression.Constant(max, type));
          return Expression.Lambda<Func<T, bool>>(maxthen, parameterExpression)
            .And(Expression.Lambda<Func<T, bool>>(minthen, parameterExpression));
        case "decimal":
          var decarray = ( (string)fieldValue ).Split(new char[] { '-' }, StringSplitOptions.RemoveEmptyEntries);
          var dmin = Convert.ToDecimal(decarray[0], CultureInfo.CurrentCulture);
          var dmax = Convert.ToDecimal(decarray[1], CultureInfo.CurrentCulture);
          var dmaxthen = Expression.GreaterThan(memberExpression, Expression.Constant(dmin, type));
          var dminthen = Expression.LessThan(memberExpression, Expression.Constant(dmax, type));
          return Expression.Lambda<Func<T, bool>>(dmaxthen, parameterExpression)
            .And(Expression.Lambda<Func<T, bool>>(dminthen, parameterExpression));
        case "float":
          var farray = ((string)fieldValue).Split(new char[] { '-' }, StringSplitOptions.RemoveEmptyEntries);
          var fmin = Convert.ToDecimal(farray[0], CultureInfo.CurrentCulture);
          var fmax = Convert.ToDecimal(farray[1], CultureInfo.CurrentCulture);
          var fmaxthen = Expression.GreaterThan(memberExpression, Expression.Constant(fmin, type));
          var fminthen = Expression.LessThan(memberExpression, Expression.Constant(fmax, type));
          return Expression.Lambda<Func<T, bool>>(fmaxthen, parameterExpression)
            .And(Expression.Lambda<Func<T, bool>>(fminthen, parameterExpression));
        case "string":
          var strarray = ( (string)fieldValue ).Split(new char[] { '-' }, StringSplitOptions.RemoveEmptyEntries);
          var smin = strarray[0];
          var smax = strarray[1];
        
          var strmethod = typeof(string).GetMethod("Contains");
          var mm = Expression.Call(memberExpression, strmethod, Expression.Constant(smin, type));
          var nn = Expression.Call(memberExpression, strmethod, Expression.Constant(smax, type));


          return Expression.Lambda<Func<T, bool>>(mm, parameterExpression)
            .Or(Expression.Lambda<Func<T, bool>>(nn, parameterExpression));
        default:
          return x => true;
      }

    }



    private static Expression<Func<T, bool>> Any<T, T2>(object fieldValue, ParameterExpression parameterExpression, MemberExpression memberExpression)
    {
      var lambda = (Expression<Func<T2, bool>>)fieldValue;
      var anyMethod = typeof(Enumerable).GetMethods(BindingFlags.Static | BindingFlags.Public)
      .First(m => m.Name == "Any" && m.GetParameters().Count() == 2).MakeGenericMethod(typeof(T2));

      var body = Expression.Call(anyMethod, memberExpression, lambda);

      return Expression.Lambda<Func<T, bool>>(body, parameterExpression);
    }

    private static PropertyDescriptor GetProperty(PropertyDescriptorCollection props, string fieldName, bool ignoreCase)
    {
      if (!fieldName.Contains('.'))
      {
        return props.Find(fieldName, ignoreCase);
      }

      var fieldNameProperty = fieldName.Split('.');
      return props.Find(fieldNameProperty[0], ignoreCase).GetChildProperties().Find(fieldNameProperty[1], ignoreCase);

    }
    #endregion
  }

  internal class SwapVisitor : ExpressionVisitor
  {
    private readonly Expression from, to;
    public SwapVisitor(Expression from, Expression to)
    {
      this.from = from;
      this.to = to;
    }
    public override Expression Visit(Expression node) => node == from ? to : base.Visit(node);
  }
  public enum OperationExpression
  {
    equal,
    notequal,
    less,
    lessorequal,
    greater,
    greaterorequal,
    contains,
    beginwith,
    endwith,
    includes,
    between,
    any
  }
}

public async Task<JsonResult> GetData(int page = 1, int rows = 10, string sort = "Id", string order = "asc", string filterRules = "")
    {
      try
      {
        var filters = PredicateBuilder.FromFilter<Company>(filterRules);
        var total = await this.companyService
                             .Query(filters)
                             .AsNoTracking()
                             .CountAsync()
                              ;
        var pagerows = (await this.companyService
                             .Query(filters)
                              .AsNoTracking()
                           .OrderBy(n => n.OrderBy(sort, order))
                           .Skip(page - 1).Take(rows)
                           .SelectAsync())
                           .Select(n => new
                           {
                             Id = n.Id,
                             Name = n.Name,
                             Code = n.Code,
                             Address = n.Address,
                             Contect = n.Contect,
                             PhoneNumber = n.PhoneNumber,
                             RegisterDate = n.RegisterDate.ToString("yyyy-MM-dd HH:mm:ss")
                           }).ToList();
        var pagelist = new { total = total, rows = pagerows };
        return Json(pagelist);
      }
      catch(Exception e) {
        throw e;
        }

    }

• 对于固定查询逻辑的封装和复用,当然除了复用还可以明显的提高代码的可读性.

public class OrderSalesQuery : QueryObject<Order>
{
    public decimal Amount { get; set; }
    public string Country { get; set; }
    public DateTime FromDate { get; set; }
    public DateTime ToDate { get; set; }

    public override Expression<Func<Order, bool>> Query()
    {
        return (x => 
            x.OrderDetails.Sum(y => y.UnitPrice) > Amount &&
            x.OrderDate >= FromDate &&
            x.OrderDate <= ToDate &&
            x.ShipCountry == Country);
    }
}

var orderRepository = new Repository<Order>(this);
    
var orders = orderRepository
    .Query(new OrderSalesQuery(){ 
        Amount = 100, 
        Country = "USA",
        FromDate = DateTime.Parse("01/01/1996"), 
        ToDate = DateTime.Parse("12/31/1996" )
    })
    .Select();

public class CustomerLogisticsQuery : QueryObject<Customer>
{
    public CustomerLogisticsQuery FromCountry(string country)
    {
        Add(x => x.Country == country);
        return this;
    }

    public CustomerLogisticsQuery LivesInCity(string city)
    {   
        Add(x => x.City == city);
        return this;
    }
}

public class CustomerSalesQuery : QueryObject<Customer>
{
    public CustomerSalesQuery WithPurchasesMoreThan(decimal amount)
    {
        Add(x => x.Orders
            .SelectMany(y => y.OrderDetails)
            .Sum(z => z.UnitPrice * z.Quantity) > amount);

        return this;
    }

    public CustomerSalesQuery WithQuantitiesMoreThan(decimal quantity)
    {
        Add(x => x.Orders
            .SelectMany(y => y.OrderDetails)
            .Sum(z => z.Quantity) > quantity);

        return this;
    }
}

var customerRepository = new Repository<Customer>(this);

var query1 = new CustomerLogisticsQuery()
    .LivesInCity("London");

var query2 = new CustomerSalesQuery()
    .WithPurchasesMoreThan(100)
    .WithQuantitiesMoreThan(10);

customerRepository
    .Query(query1.And(query2))
    .Select()
    .Dump();

以上这些都是改项目提供的方法,非常的好用