Sorting databound datagridviews

I was asked to provide sorting on a databound gridview. At first it looked easy. Just bind my generic list to the gridview and enable sorting. 

But, no can do. You cannot bind a standard generic list to a datagridview.

The solution is to create your own sortable binding list. This is the way to do it

First we create our own implementation of the list

public class SortableBindingList<T> : BindingList<T>
{
      private bool _isSorted;

      protected override bool SupportsSortingCore
      {
         get
            {
               return true;
            }
      }

      protected override void ApplySortCore(
      PropertyDescriptor property, ListSortDirection 
      direction)
      {
         List<T> items = this.Items as List<T>;
         if (items != null)
         {
            PropertyComparer<T> pc = 
            new PropertyComparer<T>(property,     
            direction);
                
            items.Sort(pc);
            _isSorted = true;
         }
         else
         {
            _isSorted = false;
         }

         this.OnListChanged(
         new ListChangedEventArgs(ListChangedType.Reset,     
         -1));
      }

      protected override bool IsSortedCore
      {
         get { return _isSorted; }
      }
}

Now it's time to implement our own sorting algorithm using reflection

public class PropertyComparer<T> : System.Collections.Generic.IComparer<T>
{
    private PropertyDescriptor _property;
    private ListSortDirection _direction;

    public PropertyComparer(PropertyDescriptor property,
        ListSortDirection direction)
    {
        _property = property;
        _direction = direction;
    }

    public int Compare(T col1, T col2)
    {
        object col1Value = GetPropertyValue(col1, 
                           _property.Name);

        object col2Value = GetPropertyValue(col2, 
                           _property.Name);

        if (_direction == ListSortDirection.Ascending)
        {
            return CompareAscending(col1Value, 
                                    col2Value);
        }
        else
        {
            return CompareDescending(col1Value,  
                                     col2Value);
        }
    }

    public bool Equals(T col1, T col2)
    {
        return col1.Equals(col2);
    }

    public int GetHashCode(T obj)
    {
        return obj.GetHashCode();
    }

    private int CompareAscending(object x, object y)
    {
        int result;

        if (x is IComparable)
        {
            result = ((IComparable)x).CompareTo(y);
        }
        else if (x.Equals(y))
        {
            result = 0;
        }
        else result = ((IComparable)x).CompareTo(y);

        return result;
    }

    private int CompareDescending(object x, object y)
    {
        return -CompareAscending(x, y);
    }

    private object GetPropertyValue(T value, string 
                                    property)
    {
        PropertyInfo propertyInfo = 
        value.GetType().GetProperty(property);
        
        return propertyInfo.GetValue(value, null);
    }
}

Now it's time to fill and bind the custom made list. lI've created this simple Person class for demonstration purposes.

dataGridView1.AutoGenerateColumns = false;

Person pers1 = new Person();
Person pers2 = new Person();
Person pers3 = new Person();
Person pers4 = new Person();

pers1.FirstName = "Glenn";
pers2.FirstName = "San";
pers3.FirstName = "Yannick";
pers4.FirstName = "Alfred";

pers1.LastName = "Goovaerts";
pers2.LastName = "Zodiac";
pers3.LastName = "Smits";
pers4.LastName = "Anvers";

pers1.Age = 6;
pers2.Age = 18;
pers3.Age = 78;
pers4.Age = 1;

pers1.BirthDate = new DateTime(2007,1,1,12,5,4);
pers2.BirthDate = new DateTime(2007,1, 1, 12, 5, 3);
pers3.BirthDate = new DateTime(2007, 1, 1, 12, 5, 5);
pers4.BirthDate = new DateTime(2005, 1, 1, 12, 5, 4);

SortableBindingList<Person> source = 
new SortableBindingList<Person>();
            
source.Add(pers1);
source.Add(pers2);
source.Add(pers3);
source.Add(pers4);

this.dataGridView1.DataSource = source;
dataGridView1.AutoResizeColumns();

The only thing we have to do now is to react to the column header click

private void dataGridView1_ColumnHeaderMouseClick
(object sender, DataGridViewCellMouseEventArgs e)
{
   DataGridViewColumn selectedColumn = 
   dataGridView1.Columns[e.ColumnIndex];
            
   ListSortDirection direction;

   if (sortedDescending == false)
   {
      direction = ListSortDirection.Descending;
      sortedDescending = true;
   }
   else
   {
      direction = ListSortDirection.Ascending;
      sortedDescending = false;
   }

   dataGridView1.Sort(selectedColumn, direction);

   selectedColumn.HeaderCell.SortGlyphDirection =
   direction == ListSortDirection.Ascending ?
   SortOrder.Ascending : SortOrder.Descending;
}

Hope this can help someone.                                           Greetz, G