How do I specify the Linq OrderBy argument dynamically? [duplicate]

Question

How do I specify the argument passed to orderby using a value I take as a parameter?

Ex:

List<Student> existingStudends = new List<Student>{ new Student {...}, new Student {...}} 

Currently implementation:

List<Student> orderbyAddress = existingStudends.OrderBy(c => c.Address).ToList(); 

Instead of c.Address, how can I take that as a parameter?

Example

 string param = "City";  List<Student> orderbyAddress = existingStudends.OrderByDescending(c => param).ToList(); 

Answer 1

You can use a little bit of reflection to construct the expression tree as follows (this is an extension method):

public static IQueryable<TEntity> OrderBy<TEntity>(this IQueryable<TEntity> source, string orderByProperty,                           bool desc)  {      string command = desc ? "OrderByDescending" : "OrderBy";      var type = typeof(TEntity);      var property = type.GetProperty(orderByProperty);      var parameter = Expression.Parameter(type, "p");      var propertyAccess = Expression.MakeMemberAccess(parameter, property);      var orderByExpression = Expression.Lambda(propertyAccess, parameter);      var resultExpression = Expression.Call(typeof(Queryable), command, new Type[] { type, property.PropertyType },                                    source.Expression, Expression.Quote(orderByExpression));      return source.Provider.CreateQuery<TEntity>(resultExpression); } 

orderByProperty is the Property name you want to order by and if pass true as parameter for desc, will sort in descending order; otherwise, will sort in ascending order.

Now you should be able to do existingStudents.OrderBy("City",true); or existingStudents.OrderBy("City",false);