Background

The idea for this post comes from a simple problem: you have a form with a GridView with two, maybe three columns. One of these contains a CheckBox which indicates a status of the object which you’re viewing and it is the only thing you need to update in that form. Because of this, you don’t want to press the ‘Edit’ button at the left of the row just to update the status of the object, but you rather you could just click on the CheckBox and that the status updates automatically. But to do that, you need to create an unbound CheckBox, meaning you can’t get that row’s unique identifier. To solve that problem, we’ll be using the OnRowDataBound and OnCheckChanged events.

Enough of the abstract stuff, time for a concrete example to see what I mean.

Example

The example will be a User table with a boolean flag which indicates if the user is active or not, and a single ASPX page which can flip the flag using an unbound ASP CheckBox.

The database

For our example, we’re going to create a simple table in MSSQL. Three columns are required, the rest is arbitrary. The table will be called ‘User’, with the following three columns: UserID (datetype: integer. int, identity specification = yes), UserName (nvarchar) and Active (bit). Any other columns can be added, but will not be used.

For a full MSSQL script for this table, look below:

The website

Now, create a new ASP.NET Website. The code behind language is irrelevant, but I’ll be doing my examples in C# since I’m more fluent in that. It’s pretty basic code, so translating it to VB.NET should not be hard.

Add a new Linq to Sql class (a DBML file), add a connection to the database your table is in and drag the table onto the design surface and save the file.

Drag a GridView (in the Toolbox, under Data) on the Default.aspx page. Go to the design view, open the smart tag and select in the ‘Choose Datasource’ drop to add a new Data source. Click on ‘LINQ’, specify an ID, click OK. On the next page, select the DataContext you just created in the DBML. Click next, select the table you want to see in the datagrid, add Where clauses if applicable. Do not enable ‘Allow update’ under Advanced. Finish the wizard.

You’ll now have a GridView and all its fiels are bound to a column specified in the database.

Using the TemplateField

The current CheckBox can not update the status when it’s being (un)checked, so let’s take care of that.

First, remove the CheckBoxField that was automatically added and which corresponds to the boolean field you want to edit without the ‘Edit’ button and replace it with the following:

<asp:TemplateField HeaderText=”[insert your text]“>
<itemtemplate>
<asp:CheckBox EnableViewState=”true” ID=”Active” runat=”server” Checked=’<%#Bind(“Active”) %>’ AutoPostBack=”true” />
</itemtemplate>
</asp:TemplateField>

This way, you get an unbound CheckBox and its Checked property will be set to the value stored in the database.

Updating the column in the database

Now there is only one single problem: when you (un)check the CheckBox, nothing happens. We’ll have to catch the event and handle it. Add the following attribute to the CheckBox you just added: OnCheckedChanged=”ChangeActiveStatus”.

In the code behind, add the following:

Once you start writing the method, you’ll encounter your last problem: because the CheckBox is unbound, you have no clue which row to update once the event is raised. We’ll solve that problem using the GridView’s OnRowDataBound event and the Attributes array of the CheckBox.

Adding the OnRowDataBound event handler

The OnRowDataBound is raised every single time a row in a GridView is being bound to a dataset. Since we’re binding the content of our LINQ datasource to our previously created GridView, this event will be raised for every row in the datasource.

Add the following Attribute to the GridView: OnDataRowBound=”onRowBound”
Lastly, add the following code to your code behind:

Whenever the OnRowDataBound event is raised, the event handler will add a custom attribute called UserID to the Attributes array and will set the value to UserID using the DataBinder.Eval method. The first argument of Eval is an object identifier, in this case the underlying data object to which the row is being bound and the second argument is a String expression which, in our case, indicates the column we’re reading from.

Now we can fill in the ChangeActiveStatus method (or whatever you called the event handler for OnCheckChanged) to update properly.
Use Convert.ToInt32(( (CheckBox) sender ).Attributes["UserID"]) to get the value stored in the attribute and to convert it to an Int. Since you’re using an unbound CheckBox, you’ll have to use a Stored Procedure or some direct SQL to update the column. For instance, your code could look like this:

Preventing the PostBack

If you absolutely hate PostBacks, then you can use some AJAX to update the field instead.