Sorting GridView using IComparer and Reflection

by David Loo | May 27, 2010 | ASP.NET, Web Development

Recently I just did a small job for a client online using IComparer interface to perform sorting on a GridView control.

First I need to create class called Person. This class is going to contain the following properties: FirstName, LastName, Age.

public class Person
{
    private string _firstName;
    private string _lastName;
    private int _age;

    public string FirstName
    {
        get { return _firstName; }
        set { _firstName = value; }
    }

    public string LastName
    {
       get { return _lastName; }
       set { _lastName = value; }
    }

    public int Age
    {
       get { return _age; }
       set { _age = value; }
    }
}

Now I need to create a class called PersonComparer that will inherit from the IComparer interface. This comparer class will be use with the Sort() method from a List collection.

 using System.Collections;
 using System.Collections.Generic;
 using System.Reflection;
 using System;

 public class PersonComparer:IComparer
 {
     private string _sortBy;

     public string SortBy
     {
         get { return _sortBy; }
         set { _sortBy = value; }
     }

     public int Compare(Person x, Person y)
     {
         int result = 0;
         string propName = string.Empty;
         string sortDirection = "ASC";

         if (_sortBy.Contains(" DESC"))
         {
             propName = _sortBy.Replace(" DESC", string.Empty).Trim();
             sortDirection = "DESC";
         }

         if (_sortBy.Contains(" ASC"))
         {
             propName = _sortBy.Replace(" ASC", string.Empty).Trim();
             sortDirection = "ASC";
         }

         // Get type of Person Object
         Type t = typeof(Person);

         // Find the property name from the sortExpress passed in SortBy property.
         PropertyInfo propInfo = t.GetProperty(propName);

         if (propInfo != null)
         {
             // Perform comparison on property value.
             result = Comparer.DefaultInvariant.Compare(propInfo.GetValue(x, null), propInfo.GetValue(y, null));

             if (sortDirection.Equals("DESC"))
             {
                 result = -result;
             }
         }
         return result;
     }
 }

(more…)