ADO.NET Cookbook

7.11. Populating a Windows Forms ComboBox

Problem

You need to populate a ComboBox from a database, bind a field in a database to the ComboBox so that the correct value is selected from the list, and use the value selected in the ComboBox to update the database.

Solution

You must:

• Fill a ComboBox from a database (pay attention to the difference between the SelectedIndex and SelectedValue).

• Bind a ComboBox to a field in a result set so that the value is selected in the ComboBox corresponding to the value in a field for the record displayed.

• Use the selection events returned by the ComboBox.

• Update the database with the value selected in the ComboBox.

The schema of table TBL0711 used in this solution is shown in Table 7-11.

Table 7-11. TBL0711 schema

Column name	Data type	Length	Allow nulls?
Id	int	4	No
ComboBoxItemId	int	4	No
Field1	nvarchar	50	Yes

The schema of table TBL0711_ComboBoxSource used in this solution is shown in Table 7-12.

Table 7-12. TBL0711_ComboBoxSource schema

Column name	Data type	Length	Allow nulls?
ComboBoxItemId	int	4	No
Description	nvarchar	50	No

The sample code contains seven event handlers:

Form.Load

Sets up the sample by creating a DataAdapter with the logic to select all records from table TBL0709 in the sample database and to update changes made back to the database. The DataAdapter is used to fill a DataTable in a new DataSet with the schema and data from TBL0709. A DataTable is filled from table TBL0709_ComboBoxSource and added to the ...