table.PrimaryKey = new DataColumn[]{table.Columns["column1"],table.Columns["column2"]}

搜索时

table.Rows.Find(New Object[]{<value in column1>, <value in column2>})

这将返回一个数据行.并且主键值必须是唯一的，否则会抛出异常.

This will return a datarow. Also the Primary key values must be unique, otherwise an exception will be thrown.