Dynamic Orderby

gistfile1.cs

public static class QueryExtensions {
    public static IQueryable<T> SortBy<T>(this IQueryable<T> source, string propertyName) {
        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;
        }
 
        ParameterExpression parameter = Expression.Parameter(source.ElementType, String.Empty);
        MemberExpression property = Expression.Property(parameter, propertyName);
        LambdaExpression lambda = Expression.Lambda(property, parameter);
 
        string methodName = (descIndex < 0) ? "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);
    }
}