SortBy

gistfile1.cs

 public static IQueryable<T> SortBy<T>(this IQueryable<T> source, string propertyName)
        {
            propertyName = propertyName.Trim();
            if (source == null)
            {
                throw new ArgumentNullException("source");
            }
            // DataSource control passes the sort parameter with a direction
            // if the direction is descending          
            int descIndex = propertyName.IndexOf(" DESC");

            if (descIndex >= 0)
            {
                propertyName = propertyName.Substring(0, descIndex).Trim();
            }

            if (String.IsNullOrEmpty(propertyName))
            {
                return source;
            }

            return source.SortBy(propertyName, descIndex > 0);
        }

        public static IQueryable<T> SortBy<T>(this IQueryable<T> source, string propertyName, bool descending)
        {
            propertyName = propertyName.Trim();
            if (source == null)
            {
                throw new ArgumentNullException("source");
            }

            if (String.IsNullOrEmpty(propertyName))
            {
                return source;
            }

            ParameterExpression parameter = Expression.Parameter(source.ElementType, String.Empty);
            MemberExpression property = Expression.Property(parameter, propertyName);
            LambdaExpression lambda = Expression.Lambda(property, parameter);

            string methodName = (!descending) ? "OrderBy" : "OrderByDescending";
            Expression methodCallExpression = Expression.Call(typeof(Queryable), methodName,
                                                              new Type[] { source.ElementType, property.Type },
                                                              source.Expression, Expression.Quote(lambda));

            return source.Provider.CreateQuery<T>(methodCallExpression);
        }