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

阿新 • • 發佈：2020-06-22

-之动态查询,查询逻辑封装复用

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

需求

配合EasyUI datagird filter实现多字段(任意字段)的筛选
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[]);

               var end = Convert.ToDateTime(datearray[]);

               this.And(x => SqlFunctions.DateDiff("d", start, x.RegisterDate) >= );

               this.And(x => SqlFunctions.DateDiff("d", end, x.RegisterDate) <= );

             }

           }

           if (rule.field == "CreatedDate" && !string.IsNullOrEmpty(rule.value))

           {

             if (rule.op == "between")

             {

               var datearray = rule.value.Split(new char[] { '-' });

               var start = Convert.ToDateTime(datearray[]);

               var end = Convert.ToDateTime(datearray[]);

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

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

             }

           }

           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[]);

               var end = Convert.ToDateTime(datearray[]);

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

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

             }

           }

           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[], or.Parameters[]).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[], and.Parameters[]).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();

    }

    private static MemberExpression GetMemberExpression<T>(ParameterExpression parameter, string propName)

    {

      if (string.IsNullOrEmpty(propName))

      {

        return null;

      }

      var propertiesName = propName.Split('.');

      if (propertiesName.Count() == )

      {

        return Expression.Property(Expression.Property(parameter, propertiesName[]), propertiesName[]);

      }

      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() == )

          {

            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() == )

          {

            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() == )

          {

            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[] + " 00:00:00", CultureInfo.CurrentCulture);

          var end = Convert.ToDateTime(datearray[] + " 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[] , CultureInfo.CurrentCulture);

          var max = Convert.ToInt32(intarray[], 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[], CultureInfo.CurrentCulture);

          var dmax = Convert.ToDecimal(decarray[], 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[], CultureInfo.CurrentCulture);

          var fmax = Convert.ToDecimal(farray[], 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[];

          var smax = strarray[];

          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() == ).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[], ignoreCase).GetChildProperties().Find(fieldNameProperty[], 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 = , int rows = , 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 - ).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;

         }

     }

配合使用的代码

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);

    }

}

查看订单的销售情况,条件金额,国家,日期

var orderRepository = new Repository<Order>(this);

var orders = orderRepository

    .Query(new OrderSalesQuery(){

        Amount = ,

        Country = "USA",

        FromDate = DateTime.Parse("01/01/1996"),

        ToDate = DateTime.Parse("12/31/1996" )

    })

    .Select();

调用查询方法

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;

    }

}

客户查询根据国家和城市查询

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;

    }

}

客户的销售情况,金额和数量

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

var query1 = new CustomerLogisticsQuery()

    .LivesInCity("London");

var query2 = new CustomerSalesQuery()

    .WithPurchasesMoreThan()

    .WithQuantitiesMoreThan();

customerRepository

    .Query(query1.And(query2))

    .Select()

    .Dump();

复用上面的定义的查询方法

以上这些都是改项目提供的方法,非常的好用