using System; using System.Collections.Generic; using System.Linq; using System.Linq.Expressions; using System.Reflection; using System.Text; using System.Threading.Tasks; namespace Apps.Common { public class LinqHelper { /// <summary> /// 排序 /// </summary> /// <typeparam></typeparam> /// <param></param> /// <param></param> /// <param></param> /// <returns></returns> public static IQueryable<T> DataSorting<T>(IQueryable<T> source, string sortExpression, string sortDirection) { //错误查询 if (string.IsNullOrEmpty(sortExpression) || string.IsNullOrEmpty(sortDirection)) { return source; } string sortingDir = string.Empty; if (sortDirection.ToUpper().Trim() == "ASC") sortingDir = "OrderBy"; else if (sortDirection.ToUpper().Trim() == "DESC") sortingDir = "OrderByDescending"; ParameterExpression param = Expression.Parameter(typeof(T), sortExpression); PropertyInfo pi = typeof(T).GetProperty(sortExpression); Type[] types = new Type[2]; types[0] = typeof(T); types[1] = pi.PropertyType; Expression expr = Expression.Call(typeof(Queryable), sortingDir, types, source.Expression, Expression.Lambda(Expression.Property(param, sortExpression), param)); IQueryable<T> query = source.AsQueryable().Provider.CreateQuery<T>(expr); return query; } /// <summary> /// 分页 /// </summary> /// <typeparam></typeparam> /// <param></param> /// <param></param> /// <param></param> /// <returns></returns> public static IQueryable<T> DataPaging<T>(IQueryable<T> source, int pageNumber, int pageSize) { if (pageNumber <= 1) { return source.Take(pageSize); } else { return source.Skip((pageNumber - 1) * pageSize).Take(pageSize); } } /// <summary> /// 排序并分页 /// </summary> /// <typeparam></typeparam> /// <param></param> /// <param></param> /// <param></param> /// <param></param> /// <param></param> /// <returns></returns> public static IQueryable<T> SortingAndPaging<T>(IQueryable<T> source, string sortExpression, string sortDirection, int pageNumber, int pageSize) { IQueryable<T> query = DataSorting<T>(source, sortExpression, sortDirection); return DataPaging(query, pageNumber, pageSize); } ///<summary> ///表达式操作 ///</summary> ///<param></param> ///<param></param> ///<returns></returns> public delegate Expression ExpressionOpretaDelegate(Expression left, Expression right); /* * if (!string.IsNullOrWhiteSpace(pager.filterRules)) * { * IEnumerable<DataFilterModel> dataFilterList = JsonHelper.DeserializeJsonToObject<List<DataFilterModel>>(pager.filterRules).Where(f => !string.IsNullOrWhiteSpace(f.value)); * queryData = LinqHelper.DataFilter<SysSample>(queryData.AsQueryable(), dataFilterList); * } */ ///<summary>///通用数据列表按过滤方法 ///</summary> ///<typeparam>过滤的数据类型</typeparam> ///<param>过滤的数据源</param> ///<paramname="dataFilterList">过滤条件集合(包含,字段名,值,操作符) </param> ///<returns></returns> public static IQueryable<T> DataFilter<T>(IQueryable<T> source, IEnumerable<DataFilterModel> datas) { T obj = System.Activator.CreateInstance<T>(); PropertyInfo[] properties = obj.GetType().GetProperties(); foreach (var item in datas) { PropertyInfo p = properties.Where(pro => pro.Name == item.field).FirstOrDefault(); //不进行无效过滤 if (p == null || item.value == null) { continue; } if (p.PropertyType == typeof(DateTime) || p.PropertyType == typeof(DateTime?)) { //时间过1滤 source = DateDataFilter<T>(source, item, p); } else { //普通过滤 source = OrdinaryDataFilter<T>(source, item, p); } } return source; } ///<summary> ///普通数据过滤 ///</summary> ///<typeparam></typeparam> ///<param></param> ///<param></param> ///<param></param> ///<retums></retums> private static IQueryable<T> OrdinaryDataFilter<T>(IQueryable<T> source, DataFilterModel item, PropertyInfo p) { //var selectvalue = Convert. // ChangeType(item.value, p.PropertyType); var option = (DataFliterOperatorTypeEnum) Enum.Parse(typeof(DataFliterOperatorTypeEnum), item.op); switch (option) { case DataFliterOperatorTypeEnum.contains: { /* 包含, 目前只支持字符串 */ source = ExpressionOperate(StringContains, source, p, item.value); break; } case DataFliterOperatorTypeEnum.equal: { /* 等于 */ source = ExpressionOperate(Expression.Equal, source, p, item.value); break; } case DataFliterOperatorTypeEnum.greater: { /* 大于 */ source = ExpressionOperate(Expression.GreaterThan, source, p, item.value); break; } case DataFliterOperatorTypeEnum.greaterorequal: { /* 大于等于 */ source = ExpressionOperate(Expression.GreaterThanOrEqual, source, p, item.value); break; } case DataFliterOperatorTypeEnum.less: { /* 小于 */ source = ExpressionOperate(Expression.LessThan, source, p, item.value); break; } case DataFliterOperatorTypeEnum.lessorequal: { /* 小于等于 */ source = ExpressionOperate(Expression.LessThanOrEqual, source, p, item.value); break; } default: break; } return (source); } ///<summary> ///时间过滤 ///</summary> ///<typeparam></typeparam> ///<param></param> ///<param></param> ///<param></param> ///<returns></returns> public static IQueryable<T> DateDataFilter<T>(IQueryable<T> source, DataFilterModel item, PropertyInfo p) { var selectDate= Convert.ToDateTime(item.value); var option= (DataFliterOperatorTypeEnum) Enum.Parse(typeof(DataFliterOperatorTypeEnum), item.op); switch(option) { case DataFliterOperatorTypeEnum.equal: { //大于0时 source=ExpressionOperate(Expression.GreaterThanOrEqual, source, p,selectDate); //小于后一天 var nextDate= selectDate.AddDays(1); source=ExpressionOperate(Expression.LessThan, source, p, nextDate); break; } case DataFliterOperatorTypeEnum.greater: { //大于等于后一天 selectDate= selectDate.AddDays(1); source=ExpressionOperate(Expression.GreaterThanOrEqual, source, p,selectDate); break; } case DataFliterOperatorTypeEnum.greaterorequal: { //大于等于当天 source=ExpressionOperate(Expression.GreaterThanOrEqual, source, p,selectDate); break; } case DataFliterOperatorTypeEnum.less: { //小于当天 source=ExpressionOperate(Expression. LessThan, source, p,selectDate); break; } case DataFliterOperatorTypeEnum.lessorequal: { //小于第二天 selectDate= selectDate.AddDays(1); source=ExpressionOperate(Expression. LessThan, source, p,selectDate); break; } default: break; } return source; } ///<summary> ///过滤操作 ///</summary> ///<typeparam></typeparam> //<typeparam></typeparam> ///<paramname="operateExpression"></ param> ///<param></param> ///<param></param> ///<param></param> ///<returns></returns> private static IQueryable<T> ExpressionOperate<T, V>(ExpressionOpretaDelegate operateExpression, IQueryable<T> source, PropertyInfo p, V value) { Expression right = null; if (p.PropertyType == typeof(Int32)) { int val = Convert.ToInt32(value); right = Expression.Constant(val, p.PropertyType); } else if (p.PropertyType == typeof(Decimal)) { Decimal val = Convert.ToDecimal(value); right = Expression.Constant(val, p.PropertyType); } else if (p.PropertyType == typeof(Byte)) { Byte val = Convert.ToByte(value); right = Expression.Constant(val, p.PropertyType); } else { right = Expression.Constant(value, p.PropertyType); } ParameterExpression param = Expression.Parameter(typeof(T), "x"); Expression left = Expression.Property(param, p.Name); Expression filter = operateExpression(left, right); Expression<Func<T, bool>> pred = Expression.Lambda<Func<T, bool>>(filter, param); source = source.Where(pred); return source; } ///<summary> ///字符串包含操作 ///</summary> ///<param></param> ///<param></param> ///<returns></returns> public static Expression StringContains(Expression left, Expression right) { Expression filter = Expression.Call(left, typeof(string).GetMethod("Contains"), right); return filter; } } }
预览效果：
总结
实现一个组合查询，只需要在原来的基础上添加几行代码
后台：