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Posted 13 May 2006

An ASP.NET DataGrid with AutoFilter

, 13 May 2006
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This article describe a DataGrid inherited web control with Excel like AutoFilter feature

Sample Image - DataGridAF1.gif


In this article I will show a new web control, a DataGrid with a HtmlSelect control in each column which allows a filter selection of items, like Microsoft Excel AutoFilter does. The control is directly inherited from System.Web.UI.WebControls.DataGrid and was tested under Microsoft IE 6.0, Mozilla FireFox 1.0.2, Netscape 7.2, Opera 7.54.

Using the code

Add the DataGridAF.dll to your project’s references and toolbox, and use it as a DataGrid base control. The only difference is a new property, ShowFilter, which allows you to show or hide the HtmlSelect controls in the columns header.

To run the demo project, unzip it under a virtual directory and start it. In the demo project, DataGridAF data are loaded from a xml file, Customers.xml (a select from Customers in Northwind database), so you don’t need to connect to a database.

The DataGridAutoFilter Class

DataGridAutoFilter class is very easy. All we need is to override two methods: OnItemDataBound and RaisePostBackEvent. The first is raised after each item is data bound to the DataGrid control and is where HtmlSelect controls are loaded (thank to Tony Truong's article for the idea); the second is used to capture the post back event raised when a HtmlSelect element is selected and is inherited from the IPostBackEventHandler interface (see this David S. Platt's book for a complete description).

OnItemDataBound Method

In this method all DataGrid items are data bound. First ListItemType.Header, then ListItemType.Item, ..., last ListItemType.Footer.

override protected void OnItemDataBound(DataGridItemEventArgs e)
    switch (e.Item.ItemType)
        case ListItemType.Header:
            // see later on
        case ListItemType.Item:
        case ListItemType.AlternatingItem:
        case ListItemType.SelectedItem:
            // see later on

        case ListItemType.Footer:
            // see later on

First Header: here is where the HtmlSelect is created, with “onchange” handler that causes a postback, it is added to an ArrayList to be accessed later on and it is added to the column header cell to be rendered. Also a SortedList object is created, but only to sort data before load in HtmlSelect.

case ListItemType.Header:
    for(int i=0; i< e.Item.Cells.Count; i++)
        // ...
        // add a select element, with "onchange" handler that causes a postback to RaisePostBackEvent;
        HtmlSelect select = new HtmlSelect();
        select.Attributes.Add("onchange", Page.GetPostBackEventReference(this));
        // add the select element to the ArrayList;
        // add a SortedList object, with an empty item;
        SortedList sorted = new SortedList();
        sorted.Add("", "");
        // load the SortedList object into the ArrayList;

Then items are data bound: here SortedList are loaded with “distinct” values of the columns.

case ListItemType.Item:
case ListItemType.AlternatingItem:
case ListItemType.SelectedItem:
    for(int i=0; i< e.Item.Cells.Count; i++)
        // fill the SortedList object with the "distinct" values from each columns;
        SortedList sorted = (SortedList)sort[i];
        if (sorted.ContainsValue(e.Item.Cells[i].Text) == false)
            sorted.Add(e.Item.Cells[i].Text, e.Item.Cells[i].Text);

Last the footer: here the sorted data are copied from the SortedList objects to the HtmlSelect controls.

case ListItemType.Footer:
    for(int i=0; i< e.Item.Cells.Count; i++)
        SortedList sorted = (SortedList)sort[i];
        HtmlSelect select = (HtmlSelect)list[i];
        // load sorted item into select element;
        for(int j=0; j< sorted.Count; j++)

RaisePostBackEvent Method

Here is were each DataGrid item is shown or hidden, according to the user selections.

public void RaisePostBackEvent(string eventArgument)
    // for each row;
    for (int i=0; i< Items.Count; i++)
        // for each column;
        for (int j=0; j< Items[i].Cells.Count; j++)
            HtmlSelect select = (HtmlSelect)list[j];
            if (select.SelectedIndex > 0)
                // hide rows with a not selected value;
                if (Items[i].Cells[j].Text != select.Items[select.SelectedIndex].Text)
                    Items[i].Visible = false;


When you have many rows in a DataGrid and you wish to select a subset of data, an AutoFilter feature may be a solution. I have not found such a control on the web, so I tried to create it. DataGridAF is not a sophisticated control, and does not allow advanced selections like Excel AutoFilter does, but it is easy to use and you can also do multiple selections, wich can be combined with sorting or paging data.


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


About the Author

stefano piuri
Web Developer
Italy Italy
I work for an Italian bank. I have 15+ years experience in bank and financial software.
I am interested in .NET (C#, ASP.NET, ...) and in SQL Server (TSQL, OLAP, ...) tecnologies.

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Comments and Discussions

GeneralRe: ASP.NET 2.0? Pin
stefano piuri16-Mar-09 3:02
memberstefano piuri16-Mar-09 3:02 
GeneralThank for the example Pin
ntgrvt20-Feb-07 12:22
memberntgrvt20-Feb-07 12:22 
GeneralRe: Thank for the example Pin
stefano piuri20-Feb-07 20:49
memberstefano piuri20-Feb-07 20:49 
QuestionError !? Pin
ttphp24-May-06 21:53
memberttphp24-May-06 21:53 
AnswerRe: Error !? Pin
stefano piuri24-May-06 23:48
memberstefano piuri24-May-06 23:48 
GeneralRe: Error !? Pin
getjacob7-Nov-06 19:32
membergetjacob7-Nov-06 19:32 
GeneralRe: Error !? Pin
stefano piuri9-Nov-06 5:34
memberstefano piuri9-Nov-06 5:34 
GeneralUseless Pin
nsimeonov17-May-06 16:15
membernsimeonov17-May-06 16:15 
Why? Because you may need filtering when you have a large dataset. However in this case you will want to use paging instead of displaying everything on one page - it's a web page, not a regular windows form and is suppose to be downloaded and processed by a browser. A 20mb page will just kill your server and then your browser for a while and I don't even want to mention the time and traffic costs.

Also you are adding dropdown lists on every column and this is wrong (I know excel does but it's a desktop application not a web page). So if you have a list of customers and cities - filtering by cities is ok while filtering by customer name is useless, however you will have a combo box with a huge list.

And last - you're populating the lists based on the displayed data and thus rendering the paging option unusable. I'm not sure how you tested this control but try a larger dataset - say 50,000 items - and chech how long does it take to display the page.

If you have less than 100 items it's easier to implement a sort feature and scroll through the list however with more than 100 items your control will generate too much traffic to be worth using it.

Filtering would be nice however if you do it like google suggest does - put input boxes, when typing something display a list of suggestions (look here) and when you select something - then you may filter the list - this way you will be able to page your dataset and also save traffic from the dropdown lists.

-- modified at 22:19 Wednesday 17th May, 2006
AnswerRe: Useless Pin
stefano piuri17-May-06 23:05
memberstefano piuri17-May-06 23:05 
GeneralIt seams to looking very good Pin
Rehan Hussain15-May-06 19:18
memberRehan Hussain15-May-06 19:18 
GeneralRe: It seams to looking very good Pin
stefano piuri15-May-06 21:29
memberstefano piuri15-May-06 21:29 

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