Biegral Blog

https://code.i-harness.com/en/q/1e79851

https://stackoverflow.com/questions/32061770/call-orderby-with-a-field-name-as-a-string/32062018

https://github.com/sonnemaf/ReflectionIT.Mvc.Paging/blob/master/src/ReflectionIT.Mvc.Paging/LinqExtensions.cs

    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 });
        }
    }

var r = new List<temp> { 
    new temp { a = 5 }, 
    new temp { a = 1 }, 
    new temp { a = 15 }
}.OrderBy("a");