EF OrderBy(string propertyname), OrderByDescending(string propertyname) 按属性排序，扩展方法

Posted 2020-08-01 计划着变化的计划

  public static class LinqExtensions
    {
        private static PropertyInfo GetPropertyInfo(Type objType, string name)
        {
            var properties = objType.GetProperties();
            var matchedProperty = properties.FirstOrDefault(p => p.Name == name);
            if (matchedProperty == null)
                throw new ArgumentException("name");

            return matchedProperty;
        }
        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;
        }

        public static IEnumerable<T> OrderBy<T>(this IEnumerable<T> query, string name)
        {
            var propInfo = GetPropertyInfo(typeof(T), name);
            var expr = GetOrderExpression(typeof(T), propInfo);

            var method = typeof(Enumerable).GetMethods().FirstOrDefault(m => m.Name == "OrderBy" && m.GetParameters().Length == 2);
            var genericMethod = method.MakeGenericMethod(typeof(T), propInfo.PropertyType);
            return (IEnumerable<T>)genericMethod.Invoke(null, new object[] { query, expr.Compile() });
        }

        public static IQueryable<T> OrderBy<T>(this IQueryable<T> query, string name)
        {
            var propInfo = GetPropertyInfo(typeof(T), name);
            var expr = GetOrderExpression(typeof(T), propInfo);

            var method = typeof(Queryable).GetMethods().FirstOrDefault(m => m.Name == "OrderBy" && m.GetParameters().Length == 2);
            var genericMethod = method.MakeGenericMethod(typeof(T), propInfo.PropertyType);
            return (IQueryable<T>)genericMethod.Invoke(null, new object[] { query, expr });
        }

        public static IEnumerable<T> OrderByDescending<T>(this IEnumerable<T> query, string name)
        {
            var propInfo = GetPropertyInfo(typeof(T), name);
            var expr = GetOrderExpression(typeof(T), propInfo);

            var method = typeof(Enumerable).GetMethods().FirstOrDefault(m => m.Name == "OrderByDescending" && m.GetParameters().Length == 2);
            var genericMethod = method.MakeGenericMethod(typeof(T), propInfo.PropertyType);
            return (IEnumerable<T>)genericMethod.Invoke(null, new object[] { query, expr.Compile() });
        }

        public static IQueryable<T> OrderByDescending<T>(this IQueryable<T> query, string name)
        {
            var propInfo = GetPropertyInfo(typeof(T), name);
            var expr = GetOrderExpression(typeof(T), propInfo);

            var method = typeof(Queryable).GetMethods().FirstOrDefault(m => m.Name == "OrderByDescending" && m.GetParameters().Length == 2);
            var genericMethod = method.MakeGenericMethod(typeof(T), propInfo.PropertyType);
            return (IQueryable<T>)genericMethod.Invoke(null, new object[] { query, expr });
        }
    }

 YourDbContext db = new  YourDbContext();

这样就可以直接使用下面这个方法了， db.TableName.OrderBy("ColumnName")， 用于动态排序时需要