Sorting Filters in Dynamic Data (DD v1.0)

This is just a small sample of how to sort your filters in Dynamic Data using the ColumnOrderAttribute from the Dynamic Data Futures project. I was surprised at how easy it was and that I’d not thought of it before.

using System;
using System.Linq;
using System.Web.DynamicData;

namespace DynamicData.CascadeExtensions
{
    /// <summary>
    /// Allows to specify the ordering of columns. 
    /// Columns are will be sorted in increasing order based 
    /// on the Order value. Columns without this attribute 
    /// have a default Order of 0. Negative values are
    /// allowed and can be used to place a column before all other columns.
    /// </summary>
    [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, 
        Inherited = true, 
        AllowMultiple = false)]
    public class ColumnOrderAttribute : Attribute, IComparable
    {

        public static ColumnOrderAttribute Default = new ColumnOrderAttribute(0);

        public ColumnOrderAttribute(int order)
        {
            Order = order;
        }

        /// <summary>
        /// The ordering of a column. Can be negative.
        /// </summary>
        public int Order { get; private set; }
        public int ListOrder { get; set; }

        public int CompareTo(object obj)
        {
            return Order - ((ColumnOrderAttribute)obj).Order;
        }
    }

    public static partial class HelperExtansionMethods
    {
        public static ColumnOrderAttribute GetColumnOrdering(this MetaColumn column)
        {
            return column.Attributes.OfType<ColumnOrderAttribute>()
                .DefaultIfEmpty(ColumnOrderAttribute.Default).First();
        }
    }
}

Listing 1 - Column Order attribute

So Listing 1 is just a direct rip off of the ColumnOrderAttribute in the Futures project. and then the code to order the filters based on the ColumnOrderAttribute.

protected void Page_Load(object sender, EventArgs e)
{
    table = GridDataSource.GetTable();
    Title = table.DisplayName;

    InsertHyperLink.NavigateUrl = table.GetActionPath(PageAction.Insert);

    // Disable various options if the table is readonly
    if (table.IsReadOnly)
    {
        GridView1.Columns[0].Visible = false;
        InsertHyperLink.Visible = false;
    }

    // set the filter order
    var filters = from c in table.Columns
                  where c is MetaForeignKeyColumn
                  orderby c.GetColumnOrdering()
                  select c;
    FilterRepeater.DataSource = filters;
    FilterRepeater.DataBind();
}

Listing 2 – modified Page_Load event handler

Here in Listing 2 you can see the code highlighted in bold italic is setting the filter sort order simples.

Note: the only caveat is that the filters are generated twice

That caveat in mind I decided to do this instead:

public class SortedFilterRepeater : FilterRepeater
{
    protected override IEnumerable<MetaColumn> GetFilteredColumns()
    {
        // sort the filters by their filter order as specified in FilterAttribute.
        // Table.Columns.Where(c => IsFilterableColumn(c))
        //     .OrderBy(column => FilterOrdering(column));
        var filteredColumns = from c in Table.Columns
                              where IsFilterableColumn(c)
                              orderby FilterOrdering(c)
                              select c;
        return filteredColumns;
    }

    protected bool IsFilterableColumn(MetaColumn column)
    {
        // don't filter custom properties by default
        if (column.IsCustomProperty) return false;

        // always filter FK columns and bools
        if (column is MetaForeignKeyColumn) return true;
        if (column.ColumnType == typeof(bool)) return true;

        return false;
    }

    private ColumnOrderAttribute FilterOrdering(MetaColumn column)
    {
        return column.Attributes
            .OfType<ColumnOrderAttribute>()
            .DefaultIfEmpty(ColumnOrderAttribute.Default)
            .First();
    }
}

Listing 3 – SortedFilterRepeater

Updated: Listing 3 is just a ripp-off on the AdvancedFilterRepeater in the Dynamic Data Futures sample.

I implemented this using by adding a mapping to the web.config as in Listing 4.

<pages>
    <tagMapping>
        <add tagType="System.Web.DynamicData.FilterRepeater"
             mappedTagType="DynamicData.CascadeExtensions.SortedFilterRepeater" />
    </tagMapping>
</pages>

Listing 4 – Adding mapping to web.config

The advantage of the above is:

1. It only generates the filters once
2. This will work with my CascadingFilters

So I think this addendum wraps this up as we have sorting of filters in Dynamic Data Preview 4.