.NET & XML

Creating a DataSet

The most obvious way to create a DataSet is to construct each of its objects and add them to the appropriate collections. First, create a new instance of DataSet named “AngusHardware.” The DataSet represents the entire database schema:

DataSet dataSet = new DataSet("AngusHardware");

Next, add a table named “customers” to the DataSet. The DataTableCollection.Add( ) method has several overloads; by passing a string parameter, you’re creating a new DataTable with the given name, and adding it to the DataSet’s Tables property. Add( ) returns the newly created DataTable, which you’ll use to create columns:

DataTable customers = dataSet.Tables.Add("customers");

Next, add a column to the “customers” table. The DataColumnCollection.Add( ) method returns the newly created DataColumn, which you’ll use in a minute to assign the primary key. This Add( ) method, like the one on DataTableCollection, has several overloads. The one used here simply takes the name of the database column and the Type of the data it contains:

DataColumn customersCustomerId = customers.Columns.Add("customer_id",
   typeof(long));

The process is similar for each column. Note that some columns are nullable in the database and others are not; the AllowDBNull property indicates whether the column is nullable:

customers.Columns.Add("name",typeof(string)).AllowDBNull = false; customers.Columns.Add("address1",typeof(string)).AllowDBNull = false; customers.Columns.Add("address2",typeof(string)); customers.Columns.Add("address3",typeof(string)); ...