Linq Order by when column name is dynamic and pass as a string to a function - linq

Question

I have a Linq (Entity Framework) Query as
function getData(string col_to_sort , bool IsAscending , int pageNo , int pageSize)
{
context.table_name.Skip(pageNo*pageSize).Take(pageSize).ToArray();
}
What i want is that if i pass the name of the column as a parameter to the function
and the order it will sort my query too.
Since my column name will be a string so we might need to convert it to ObjectQuery.
How can i achieve this?
Any help is appreciated

Answer 1

You can use Dynamic Linq:
string direction = IsAscending ? " ASC" : " DESC";
context.table_name.OrderBy(col_to_sort + direction).Skip(pageNo*pageSize).Take(pageSize).ToArray();

Answer 2

If you are using Dynamic Linq, then the accepted answer will work.
But If you don't want to add an extra library (Dynamic Linq), then you can pick my first approach. I will explain both the approaches where you have or don't have Dynamic Linq. You can select based on your preferences and choice.
First Approach: When you don't have Dynamic Linq:
If you are using using System.Linq; instead of using System.Linq.Dynamic.Core, then you can use this approach:
orderBy is the string and Student is the T (The Entity, in which we want to search).
Create a Utility class, something like this: (you can anytime covert to extension method If you wish.)
public static class LinqUtility
{
public static Expression<Func<T, object>> ToLambda<T>(string propertyName)
{
var parameter = Expression.Parameter(typeof(T));
var property = Expression.Property(parameter, propertyName);
var propAsObject = Expression.Convert(property, typeof(object));
return Expression.Lambda<Func<T, object>>(propAsObject, parameter);
}
}
And you can use like this:
public async Task<IList<Student>> GetStudents(long groupId, string orderBy, Filter filter)
{
return await _context.Students.Where(x => x.StudentGroupId == groupId)
.OrderByDescending(LinqUtility.ToLambda<Student>(orderBy))
.Skip(filter.Skip)
.Take(filter.Take)
.ToListAsync();
}
Second Approach: When you have Dynamic Linq:
The Dynamic LINQ library exposes a set of extension methods on IQueryable corresponding to the standard LINQ methods at Queryable, and which accept strings in a special syntax instead of expression trees.
You need to include the Library separately. Include System.Linq.Dynamic.Core. The Author of this Library is not Microsoft.. As such no harm in using it.
So, this Library, provides you a method, that accepts the string.
You can pass comma separated values as well in string, this can be achieved by above code as well, but some changes would be required.
In the same example, just pass orderBy:
public async Task<IList<Student>> GetStudents(long groupId, string orderBy, Filter filter)
{
return await _context.Students.Where(x => x.StudentGroupId == groupId)
.OrderBy(orderBy)
.Skip(filter.Skip)
.Take(filter.Take)
.ToListAsync();
}