using System;

 using System.Collections.Generic;

 using System.Linq;

 using System.Linq.Expressions;

 using System.Reflection;

 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 == );

         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 == );

         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 == );

         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 == );

         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 =  },

    new temp { a =  },

    new temp { a =  }

}.OrderBy("a");