Question

Ok, I found this, which will allow me to do this:

public IList<Item> GetItems(string orderbyColumn)
{
    return _repository.GetItems().OrderBy(orderByColumn).ToList();
}

Is this the best way to do “dynamic” ordering? I want to be able to pass the column name as a string (and the sort direction) to my Service, and have it order the correct way.

Answer 1

If you’re just after dynamic sorting without the full Dynamic-Linq stuff you can check out a post I wrote about this a while back: click

EDIT: I don’t really blog anymore so here’s the actual extension method:

public static IQueryable<TEntity> OrderBy<TEntity>(this IQueryable<TEntity> source, string sortExpression) where TEntity : class
    {
        if (string.IsNullOrEmpty(sortExpression))
            return source; // nothing to sort on

        var entityType = typeof(TEntity);
        string ascSortMethodName = "OrderBy";
        string descSortMethodName = "OrderByDescending";            
        string[] sortExpressionParts = sortExpression.Split(' ');
        string sortProperty = sortExpressionParts[0];
        string sortMethod = ascSortMethodName;

        if (sortExpressionParts.Length > 1 && sortExpressionParts[1] == "DESC")
            sortMethod = descSortMethodName;    

        var property = entityType.GetProperty(sortProperty);
        var parameter = Expression.Parameter(entityType, "p");
        var propertyAccess = Expression.MakeMemberAccess(parameter, property);
        var orderByExp = Expression.Lambda(propertyAccess, parameter);

        MethodCallExpression resultExp = Expression.Call(
                                            typeof(Queryable), 
                                            sortMethod, 
                                            new Type[] { entityType, property.PropertyType },
                                            source.Expression, 
                                            Expression.Quote(orderByExp));

        return source.Provider.CreateQuery<TEntity>(resultExp);
    }