Working with Columns
The schema for a table is defined by the columns in the table and the
constraints on those columns. Columns belonging to the
DataTable
are stored as
DataColumn
objects in a
DataColumnCollection
object and are accessed
through the Columns
property of the
DataTable
. This section examines some methods and
properties of the DataColumnCollection
.
There are two methods that can add a column to a table. The
Add( )
method optionally takes arguments
that specify the name, type, and expression of the column to be
added. An existing column can be added by passing a reference to an
existing column. If no arguments are passed, the default names
Column1
, Column2
,
Column3
, and so on are assigned to the new
columns. The following examples show how to create columns within the
table:
// adding a column using a reference to an existing column DataColumn col = new DataColumn("MyColumn, typeof(System.Int32)); dt.Columns.Add(col); // adding and creating a column in the same statement dt.Columns.Add("MyColumn", typeof(System.Int32));
The second method for adding columns is the AddRange( )
method, which allows more than one column stored in a
DataColumn
array to be added to the table in a
single statement, as shown in the following example:
DataTable dt = new DataTable("MyTable"); // create and add two columns to the DataColumn array DataColumn[] dca = new DataColumn[] {new DataColumn("Col1", typeof(System.Int32)), new DataColumn("Col2", typeof(System.Int32))}; // add the columns in ...
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