How to: Create an Expression Column (Visual Basic) 

This example creates a DataColumn object and sets the DataColumn.Expression property to calculate the order total (without the discount!).

Example

Private Sub CreateExpressionColumn()

    Dim orderTotal As New DataColumn()
    orderTotal.ColumnName = "OrderTotal"
    orderTotal.DataType = GetType(Double)

    orderTotal.Expression = "UnitPrice * Quantity"

    dsNorthwind1.Order_Details.Columns.Add(orderTotal)
End Sub

Compiling the Code

This example requires:

• A project reference to System.data.dll.

• Access to the members of the System.Data namespace. Add an Imports statement if you are not fully qualifying member names in your code. For more information, see Imports Statement.

• An instance of a typed dataset named dsNorthwind1.

• The OrderDetails table in the dsNorthwind1 dataset.

Robust Programming

The following conditions may cause an exception:

• The database is unavailable (OleDbException Class, SqlException Class, OdbcException Class, or OracleException Class, exception will be specific to your database).

See Also

Reference

DataColumn.DataType Property

Concepts

Creating Expression Columns
Adding Columns to a Table

Other Resources

Accessing Data (Visual Studio)
ADO.NET
Preparing Your Application to Receive Data
Editing Data in Your Application