DataColumn objects represent the columns, that is, the fields, in a data table. In ADO.NET terms, the columns in a table specify its XML schema. When you create a table and add columns to it, you specify the name of the column and the type of data it stores; see the DataTableCode example in the "Creating a Data Table in Code" topic in this chapter for the details.
You can make sure that values in a data column are unique by creating a UniqueConstraint object and adding it to the Constraints collection of the containing DataTable object.
You can use the Expression property of data columns to perform operations such as filtering rows, calculating values, or creating sums.