using System;
using System.Data;
class Program
{
static void Main(string[] args)
{
DataTable dt1 = new DataTable("Table-1");
DataColumn pkCol = dt1.Columns.Add("Id", typeof(int));
dt1.Columns.Add("Field1", typeof(string)).MaxLength = 50;
dt1.PrimaryKey = new DataColumn[] { pkCol };
DataTable dt2 = new DataTable("Table-2");
dt2.Columns.Add("Id", typeof(int));
dt2.Columns.Add("Field1", typeof(string)).MaxLength = 50;
UniqueConstraint uc = new UniqueConstraint("PrimaryKey-2", dt2.Columns["Id"], true);
dt2.Constraints.Add(uc);
DataTable dt3 = new DataTable("Table-3");
dt3.Columns.Add("Id1", typeof(int));
dt3.Columns.Add("Id2", typeof(int));
dt3.Columns.Add("Field1", typeof(string)).MaxLength = 50;
dt3.Constraints.Add("PrimaryKey-3",new DataColumn[] { dt3.Columns["Id1"], dt3.Columns["Id2"] },true);
}
}