"Automatic sorting is only supported with DataView, DataTable, and DataSet" or else How to sort list in ObjectDataSource

October 7, 2008

When I wanted to sort GridView which used ObectDataSource I obtained exception Automatic sorting is only supported with DataView. (WTF!! why?!)

So, becouse I changed my job I wanted to solve this problem ASAP.

First at all you should do is

make your universal Comparer.
Update data object for ObjectDataSource
Update code behind for your page
Update ASPX file – sortable columns + add ObjectDatasource parameters

UniversalComparer

/// <summary>
/// Provides universal comparing for particular UDT’s.
/// </summary>
/// <typeparam name=”T”></typeparam>
/// <example>listBO.Sort(new UniversalComparer<BO>(sortExpression, SortDirection.Ascending));</example>
public class UniversalComparer<T> : IComparer<T>
{
private readonly string _sortExpression;
private readonly short _sortDirection;
public UniversalComparer(string expression, SortDirection sortDirection)
{
_sortExpression = expression;
_sortDirection = (short)sortDirection;
}

/// <summary>
/// Compares two objects and returns a value indicating whether one is less than, equal to, or greater than the other.
/// </summary>
/// <param name=”x”>The first object to compare.</param>
/// <param name=”y”>The second object to compare.</param>
/// <returns>
/// Value Condition Less than zero<paramref name=”x”/> is less than <paramref name=”y”/>.Zero<paramref name=”x”/> equals <paramref name=”y”/>.Greater than zero<paramref name=”x”/> is greater than <paramref name=”y”/>.
/// </returns>
public int Compare(T x, T y)
{
if (string.IsNullOrEmpty(_sortExpression)) return 0;
Type t = x.GetType();
PropertyInfo pInfo = t.GetProperty(_sortExpression);
if (pInfo != null)
return (_sortDirection) * Comparer.DefaultInvariant.Compare(pInfo.GetValue(x, null), pInfo.GetValue(y, null));
throw new NullReferenceException(string.Format(“Property doesn’t exists in the instance”));
}

/// <summary>
/// Determinates direction of sorting.
/// </summary>
public enum SortDirection
{
Ascending = 1,
Descending = -1
}
}

Update code behind for your page

Add delegated method which is calling when Sorting event is fired.

protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
{
ObjectDataSource1.SelectParameters["sortExpression"].DefaultValue = e.SortExpression;
ObjectDataSource1.SelectParameters["sortDirection"].DefaultValue = RevertSortDirection(ObjectDataSource1.SelectParameters["sortDirection"].DefaultValue);
e.Cancel = true;
}

/// <summary>
/// Reverts the sort direction, which is parsed from string. Return value and input parameters are in string format.
/// Values must be equal to Values of SortDirection enum.
/// </summary>
/// <param name=”sortDirectionString”>The sort direction string.</param>
/// <returns></returns>
private string RevertSortDirection(string sortDirectionString)
{
SortDirection sortDirection ;
if (string.IsNullOrEmpty(sortDirectionString))
sortDirection = SortDirection.Descending;
else
sortDirection = (SortDirection) Enum.Parse(typeof(SortDirection), sortDirectionString, false);
SortDirection direction = sortDirection == SortDirection.Ascending ? SortDirection.Descending : SortDirection.Ascending;
return Enum.GetName(typeof(SortDirection), direction);
}

e.Cancel = true – this is very important line which tell us, that firing event must be cancelled in this moment. In other words: It block Automatic sorting is only supported with DataView error

Update DataSource of ObjectDataSource

In this part I will update SELECT for ObjectDataSource

public List<BO> GetBOs(string sortExpression, string sortDirection)
{
listBO.Add(new BO(10, “Kolar”));
listBO.Add(new BO(11, “Kopecky”));
listBO.Add(new BO(10, “Pavel”));
listBO.Add(new BO(12, “Banan”));
listBO.Add(new BO(14, “Opice”));

if (!string.IsNullOrEmpty(sortExpression))
{
if (string.IsNullOrEmpty(sortDirection) || sortDirection.ToUpper() == “DESCENDING”)
listBO.Sort(new UniversalComparer<BO>(sortExpression, UniversalComparer<BO>.SortDirection.Ascending));
else
listBO.Sort(new UniversalComparer<BO>(sortExpression, UniversalComparer<BO>.SortDirection.Descending));
}
return listBO;
}

For Select method I am telling which column and how to sort.

Update ASPX ObjectdataSource + Grid

<asp:ObjectDataSource ID=”ObjectDataSource1″ runat=”server” SelectMethod=”GetBOs” TypeName=”BOListDataSource”>
<SelectParameters>
<asp:Parameter Name=”sortExpression” Type=”string” Direction=”input” />
<asp:Parameter Name=”sortDirection” Type=”string” Direction=”input” />
</SelectParameters>
</asp:ObjectDataSource>
</form>

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