ADO.NET Visual Support: The Binding Source

The controls of a Windows application are meant to serve all types of applications, not just databases. If you want a Windows control of your application to use the values of your database, you must create a type of link between the control and the column of a table. This process is referred to as binding. The object that serves this connection is referred to as a binding source.

To support binding sources, the .NET Framework provides the BindingSource class from the System.Windows.Forms namespace. To visually create a binding source, from the Data section of the Toolbox, you can click BindingSource and click the form or container of your application. Because it is a non-visual object, its label would be positioned under the form. You can then specify its characteristics in the Properties window.

To programmatically create a binding source, you can declare a variable of type BindingSource. The class is equipped with three constructors. The default constructor allows you to simply declare the variable. Here is an example:

private void btnBindingSource_Click(object sender, EventArgs e)
{
    BindingSource bsNames = new BindingSource();
}

If you create a binding source, obviously you must give it a name. If you create it from the Toolbox, you can accept or change its name in the Properties window. Besides its name, the second most important detail of a binding source is the list that holds its values. This list is referred to as the data source. To make the binding source as flexible as possible, the data source can be almost any type of list, including an array. In reality, any class that implements the IList interface is a candidate to be a data source.

To support data sources, the BindingSource class is equipped with a property named DataSource, which is of type object. The idea of using the vague object type indicates that many types, but not all types, of objects or lists can be used as data sources.

To programmatically specify the data source of a binding source, first create your list, then assign it to the DataSource property of your BindingSource object. Here is an example:

private void btnBindingSource_Click(object sender, EventArgs e)
{
    BindingSource bsNames = new BindingSource();
    List<string> strNames = new List<string>();

    strNames.Add("Vicky Bisso");
    strNames.Add("Amy Warren");
    strNames.Add("Chrissie Childs");
    strNames.Add("Martial Otto");

    bsNames.DataSource = strNames;
}

To visually specify the data source of a binding source, access the Properties window of your BindingSource object. In the Properties window, click DataSource and click the arrow of its combo box:

• If you had not previously created a data source, you can click Add Project Data Source... This would launch the Data Source Configuration Wizard that allows you to create and configure a data set
• If you had previously created a data set object, you can expand the Other Data Sources node and expand the Project Data Sources node. You would see the created data set and you can select it. Here is an example: