Helper class to pass dynamic orderby parameter in LINQ.

DynamicOrderByHelper.cs

///<summary>
/// Usage - 
/// if (QueryHelper.PropertyExists<Club>(orderBy))
/// {
///   query = query.OrderByProperty(orderBy);
///   - OR - 
///   query = query.OrderByPropertyDescending(orderBy);
/// }
///</summary>
public static class QueryHelper
{
    private static readonly MethodInfo OrderByMethod =
        typeof (Queryable).GetMethods().Single(method => 
        method.Name == "OrderBy" && method.GetParameters().Length == 2);

    private static readonly MethodInfo OrderByDescendingMethod =
        typeof (Queryable).GetMethods().Single(method => 
        method.Name == "OrderByDescending" && method.GetParameters().Length == 2);

    public static bool PropertyExists<T>(string propertyName)
    {
        return typeof(T).GetProperty(propertyName, BindingFlags.IgnoreCase | 
            BindingFlags.Public | BindingFlags.Instance) != null;
    }

    public static IQueryable<T> OrderByProperty<T>(
       this IQueryable<T> source, string propertyName)
    {
        if (typeof (T).GetProperty(propertyName, BindingFlags.IgnoreCase | 
            BindingFlags.Public | BindingFlags.Instance) == null)
        {
            return null;
        }
        ParameterExpression paramterExpression = Expression.Parameter(typeof (T));
        Expression orderByProperty = Expression.Property(paramterExpression, propertyName);
        LambdaExpression lambda = Expression.Lambda(orderByProperty, paramterExpression);
        MethodInfo genericMethod = 
          OrderByMethod.MakeGenericMethod(typeof (T), orderByProperty.Type);
        object ret = genericMethod.Invoke(null, new object[] {source, lambda});
        return (IQueryable<T>) ret;
    }

    public static IQueryable<T> OrderByPropertyDescending<T>(
        this IQueryable<T> source, string propertyName)
    {
        if (typeof (T).GetProperty(propertyName, BindingFlags.IgnoreCase | 
            BindingFlags.Public | BindingFlags.Instance) == null)
        {
            return null;
        }
        ParameterExpression paramterExpression = Expression.Parameter(typeof (T));
        Expression orderByProperty = Expression.Property(paramterExpression, propertyName);
        LambdaExpression lambda = Expression.Lambda(orderByProperty, paramterExpression);
        MethodInfo genericMethod = 
          OrderByDescendingMethod.MakeGenericMethod(typeof (T), orderByProperty.Type);
        object ret = genericMethod.Invoke(null, new object[] {source, lambda});
        return (IQueryable<T>) ret;
    }
}