create type test_type as (id int, descr text);
create table test(id serial primary key, test test_type not null);

insert into test values
(default, row( 1 ,'test1')),
(default, row( 2 ,'test2')),
(default, row( 3 ,'test3')),
(default, row( 4 ,'test4')),
(default, row( 5 ,'test5')),
(default, row( 6 ,'test6')),
(default, row( 7 ,'test7'));

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace test_comp_types
{
    public partial class frmMain : Form
    {
        ToolStrip menu; SourceGrid.DataGrid dg;

        Npgsql.NpgsqlConnection con;
        Npgsql.NpgsqlDataAdapter da;

        DataTable dt;

        public frmMain()
        {
            InitializeComponent();

            dg = new SourceGrid.DataGrid(); dg.Dock = DockStyle.Fill; this.Controls.Add(dg);
            menu = new ToolStrip(); menu.Dock = DockStyle.Top; this.Controls.Add(menu);

            this.Load += new EventHandler(frmMain_Load);
        }

        void frmMain_Load(object sender, EventArgs e)
        {
            con = new Npgsql.NpgsqlConnection("server=localhost;port=5432;database=test;uid=test;pwd=1;encoding=unicode;");
            con.Open();
            da = new Npgsql.NpgsqlDataAdapter("select * from test", con);
            //da.InsertCommand=new 
            dt = new DataTable();
            da.Fill(dt);
            dg.DataSource =new DevAge.ComponentModel.BoundDataView(dt.DefaultView);

            //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
            menu.Items.Add(new ToolStripLabel("dt.Columns[\"test\"].DataType.FullName="
                +dt.Columns["test"].DataType.FullName));
            //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
        }
    }
}

 
Npgsql.NpgsqlCommandBuilder bdr = new Npgsql.NpgsqlCommandBuilder(da);
menu.Items.Add("SAVE", null, delegate { da.Update(dt); });

da.InsertCommand = new Npgsql.NpgsqlCommand("insert into test values(default,:test::test_type);"
                + "select * from test where id=lastval();", con);
            da.InsertCommand.Parameters.Add(":test", NpgsqlTypes.NpgsqlDbType.Text,  0 , "test");

            da.UpdateCommand = new Npgsql.NpgsqlCommand("update test set test=:test::test_type where id=:id;"
                + "select * from test where id=:id;", con);
            da.UpdateCommand.Parameters.Add(":id", NpgsqlTypes.NpgsqlDbType.Integer,  4 , "id");
            da.UpdateCommand.Parameters[":id"].SourceVersion = DataRowVersion.Original;
            da.UpdateCommand.Parameters.Add(":test", NpgsqlTypes.NpgsqlDbType.Text,  0 , "test");

            da.DeleteCommand = new Npgsql.NpgsqlCommand("delete from test where id=:id;", con);
            da.DeleteCommand.Parameters.Add(":id", NpgsqlTypes.NpgsqlDbType.Integer,  4 , "id");
            da.DeleteCommand.Parameters[":id"].SourceVersion = DataRowVersion.Original;

            dg.Columns[ 0 ].DataCell.Editor = null;

            menu.Items.Add("SAVE", null, delegate { da.Update(dt); });