linq sort

来源：互联网发布：淘宝店怎么才能有生意编辑：程序博客网时间：2024/06/08 04:37

传入排序的格式为 it.groupid desc 或 it.groupname asc 等

        static IOrderedQueryable<T> ApplyOrder<T>(IQueryable<T> source, string property)
        {
            string methodName = "OrderBy";
            string[] props = property.Split('.'); Type type = typeof(T);
            ParameterExpression arg = Expression.Parameter(type, "x"); Expression expr = arg;
            string prop = props[1].Split(' ')[0];
            string sort = props[1].Split(' ')[1];

            if (sort.Equals("desc"))
            {
                methodName = "OrderByDescending";
            }
            if (sort.Equals("asc"))
            {
                methodName = "OrderBy";
            }

            PropertyInfo pi = type.GetProperty(prop);
            expr = Expression.Property(expr, pi);
            type = pi.PropertyType;

            //foreach (string prop in props)
            //{             // use reflection (not ComponentModel) to mirror LINQ
            //    PropertyInfo pi = type.GetProperty(prop);
            //    expr = Expression.Property(expr, pi);
            //    type = pi.PropertyType;
            //}
            Type delegateType = typeof(Func<,>).MakeGenericType(typeof(T), type);
            LambdaExpression lambda = Expression.Lambda(delegateType, expr, arg);
            object result = typeof(Queryable).GetMethods().Single(
                method => method.Name == methodName
                && method.IsGenericMethodDefinition
                && method.GetGenericArguments().Length == 2
                && method.GetParameters().Length == 2)
                .MakeGenericMethod(typeof(T), type)
                .Invoke(null, new object[] { source, lambda });
            return (IOrderedQueryable<T>)result;
        }

调用：

public IQueryable<gps_drivers> GetGps_driversBySort(string sort, string keyword, string userloginname)

{

var item=from x in ObjectContext.gps_drivers
                             join y in this.ObjectContext.gps_group_users on x.GroupID equals y.GroupID
                             where y.UserLoginName.Equals(userloginname)
                              select x ;
                    int i = item.Count();
                    return ApplyOrder<gps_drivers>(item, sort);

}

参考 http://stackoverflow.com/questions/41244/dynamic-linq-orderby

        static IOrderedQueryable<T> ApplyOrder<T>(IQueryable<T> source, string property, string methodName) {
            string[] props = property.Split('.');
            Type type = typeof(T);
            ParameterExpression arg = Expression.Parameter(type, "x");
            Expression expr = arg;         foreach(string prop in props)
            {             // use reflection (not ComponentModel) to mirror LINQ
                PropertyInfo pi = type.GetProperty(prop);
                expr = Expression.Property(expr, pi);
                type = pi.PropertyType;
            }
            Type delegateType = typeof(Func<,>).MakeGenericType(typeof(T), type);
            LambdaExpression lambda = Expression.Lambda(delegateType, expr, arg);
            object result = typeof(Queryable).GetMethods().Single(
               method => method.Name == methodName
               && method.IsGenericMethodDefinition
               && method.GetGenericArguments().Length == 2
               && method.GetParameters().Length == 2)
               .MakeGenericMethod(typeof(T), type)
               .Invoke(null, new object[] { source, lambda });
            return (IOrderedQueryable<T>)result;

}