Creating Expression Columns
An expression column can be created to
perform calculations on columns in the row or aggregations on a
collection of rows. No data is actually stored in the column, and the
expression value is evaluated when the column is read. Setting the
Expression
property to anything other than an
empty string automatically sets the
ReadOnly
property of the column to
true
. If the expression isn’t
valid, an EvaluateException
is raised.
// calculate the extended price for the the order detail line DataColumn col1 = new DataColumn("Quantity", typeof(System.Int32)); DataColumn col2 = new DataColumn("Price", typeof(System.Decimal)); // create a column calculating the extended price DataColumn col3 = new DataColumn("ExtendedPrice", typeof(System.Decimal)); Col3.Expression = "Quantity * Price";
Get ADO.NET in a Nutshell now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.