Mar 03 2011

Sort Generic List Using Lambda Expression For Dynamic Type And Dynamic Property

Category: .net,Lambda,LINQJebarson Jebamony @ 9:46 am

I once stuck on a requirement where I needed to write a code which is flexible and generic enough to sort any type of collection and also the property based on which it has to be sorted will be dynamic. After trying many options I discovered myself how easy it is to hit this requirement using Lamda Expression.

Below code will do this for you.

public class Utility<T>
{
        /// <Summary>
        /// Gets the sorted list.
        /// </Summary>
        /// <param name="source" />The source.
        /// <param name="sortColumn" />The sort column.
        /// <param name="sortDirection" />The sort direction.
        /// <The sorted list. />
        private List<T> GetSortedList(List<T> source, string sortColumn, SortDirection sortDirection)
        {
            // Prepare the dynamic sort expression
            var paramExp = Expression.Parameter(typeof(T), typeof(T).ToString());
            Expression propConvExp = 
                             Expression.Convert(Expression.Property(paramExp, sortColumn), typeof(object));
            var sortExp = Expression.Lambda>(propConvExp, paramExp);

            if (sortDirection == SortDirection.Ascending)
            {
                return source.AsQueryable().OrderBy(sortExp).ToList();
            }
            else
            {
                return source.AsQueryable().OrderByDescending(sortExp).ToList();
            }
        }
}

We will call this method as below

List<Employee> sortedEmployees 
= new Utility<Employee>().GetSortedList(employeeList, "City", SortDirection.Ascending);

First we create the parameter expression for the generic type and on the further two statements we are promting the expression to convert the dynamic property based on which we need to sort to a understandable format of lambda. Then we go ahead and use the sort of generic list.

Aren’t you loving lambda expressions?

7 Responses to “Sort Generic List Using Lambda Expression For Dynamic Type And Dynamic Property”

  1. kashif abbas says:

    I'm unable to use your code. What is the "Expression" is it lambda expression or some type. If it is a type then what is its namespace???
    Looks to be a gud post but useless for me so far. It always says "Expression does not exists in the current context.

  2. jebarson says:

    Kashif use System.Linq.Expressions

  3. Sruthi says:

    Iam m getting error in that statement :try specifying the arguments explicitly..

    return source.AsQueryable().OrderBy(sortExp).ToList();
    i added namespaces system.collections.generic;system.Linq.Expressions;
    Could any one help me regarding this..

  4. jebarson says:

    Sruthi Please mail me your code

  5. Microsoft Programmers » Dynamic Lambda Expression For Sorting A List / Collection Using Complex Types Without Implementing IComparable says:

    [...] my previous post we discussed on sorting the list / collection using dynamic lambda expression for prop…. In this article we will see how to sort on complex [...]

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