.net core efcore 动态 orderby

文章转载自：https://www.cnblogs.com/Extnet/p/9848272.html

前端采用Datatable插件生成的table，自带的排序请求，发送到后台例如： title asc ,此时需要把字符串转换成efccore的查询排序方式，因此完成动态生成orderby。这样可以根据前端传的字段来动态排序了。
调用方式：

await data.OrderBy(order[0], order[1] == "desc").Skip(page).Take(limit).ToListAsync().ConfigureAwait(false);

以下是生成方法

using System;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;

namespace Flyinghat.Common.Extensions
{
    public static class LinqExtensions
    {
        public static IQueryable OrderBy(this IQueryable query, string field, bool desc)
        {
            if (!string.IsNullOrWhiteSpace(field))
            {
                ParameterExpression p = Expression.Parameter(typeof(T));
                Expression key = Expression.Property(p, field);
                var propInfo = GetPropertyInfo(typeof(T), field);
                var expr = GetOrderExpression(typeof(T), propInfo);
                if (desc)
                {
                    var method = typeof(Queryable).GetMethods().FirstOrDefault(m => m.Name == "OrderByDescending" && m.GetParameters().Length == 2);
                    var genericMethod = method.MakeGenericMethod(typeof(T), propInfo.PropertyType);
                    return (IQueryable)genericMethod.Invoke(null, new object[] { query, expr });
                }
                else
                {
                    var method = typeof(Queryable).GetMethods().FirstOrDefault(m => m.Name == "OrderBy" && m.GetParameters().Length == 2);
                    var genericMethod = method.MakeGenericMethod(typeof(T), propInfo.PropertyType);
                    return (IQueryable)genericMethod.Invoke(null, new object[] { query, expr });
                }
            }
            return query;
        }
        /// 

        /// 获取反射
        /// 
        /// 
        /// 
        /// 
        private static PropertyInfo GetPropertyInfo(Type objType, string name)
        {
            var properties = objType.GetProperties();
            var matchedProperty = properties.FirstOrDefault(p => p.Name.Equals(name, StringComparison.OrdinalIgnoreCase));
            if (matchedProperty == null)
                throw new ArgumentException("对象不包含指定属性名");

            return matchedProperty;
        }
        /// 

        /// 获取生成表达式
        /// 
        /// 
        /// 
        /// 
        private static LambdaExpression GetOrderExpression(Type objType, PropertyInfo pi)
        {
            var paramExpr = Expression.Parameter(objType);
            var propAccess = Expression.PropertyOrField(paramExpr, pi.Name);
            var expr = Expression.Lambda(propAccess, paramExpr);
            return expr;
        }
    }
}