C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Npgsql;
using NpgsqlTypes;
using WindowsFormsApplication1.Beans;

namespace WindowsFormsApplication1
{
    public partial class inscription : Form
    {
        public static Client client;
        DateTime date;
        string Conx = "Server=localhost;Port=5432;Database=postgres;User=postgres;pwd=yannick93";
        NpgsqlCommand MyCmd = null;
        NpgsqlConnection MyCnx = null;
        public inscription()
        {
            InitializeComponent();
        }

        private void label1_Click(object sender, EventArgs e)
        {

        }

        private void label4_Click(object sender, EventArgs e)
        {

        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void b_annuler1_Click(object sender, EventArgs e)
        {

        }

        private void b_confirm1_Click(object sender, EventArgs e)
        {

            String nom = esp_nom.Text;
            String prenom = esp_prenom.Text;
            String adr = esp_adr.Text;
            String ville = esp_ville.Text;
            String pass = esp_pass.Text;
            String confirm = esp_conf.Text;
            if (nom == "" || prenom == "" || adr == "" || ville == "" || pass == "" || confirm == "")
            {
                MessageBox.Show("veuiller entrer tous les parametres", "parametres manquants");
            }
            else
            {
                if (!pass.Equals(confirm))
                {
                    MessageBox.Show("veuillez bien saisir votre mot de pass", "erreur de confirmation");
                }
                else
                {
                    Connexion connect = new Connexion();
                    try
                    {
                        // connect.con.Open();
                        date = DateTime.Now;
                        String dateh = date.ToShortTimeString();
                        String datej = date.ToShortDateString();
                        var tabh = dateh.Split(':');
                        var tabj = datej.Split('/');
                        String h = tabh[0];
                        String m = tabh[1];
                        String j = tabj[0];
                        String mois = tabj[1];
                        String an = tabj[2];
                        String dnom = nom.Substring(0, 1);
                        String id = "dif-" + dnom + h + m + j + mois + an;


                        client = new Client(id, nom, prenom, adr, ville, pass);


                        string insert = "INSERT INTO client(id,nom,prenom,adr,ville,pass) values('" + client.id + "','" + client.nom + "','" + client.prenom + "','" + client.adr + "','" + client.ville + "','" + client.pass + "')";
                        MessageBox.Show("erreur d'accessibilite 2", "error2");
                        NpgsqlCommand MyCmd = connect.con.CreateCommand();
                        MyCmd.CommandText = insert;
                        MessageBox.Show("erreur d'accessibilite3", "error3");
                        MyCmd.ExecuteNonQuery();
                        MessageBox.Show("erreur d'accessibilite4", "error4");
                        connect.con.Close();
                        MessageBox.Show(dateh, datej);
                    }
                    catch (Exception)
                    {
                        MessageBox.Show("erreur d'accessibilite", "error");
                    }
                }
            }
        }

        public void InsertPersons(string nom, string prenom, string tel, string adresse)
        {
            MyCnx = new NpgsqlConnection(Conx);
            string insert = "INSERT INTO \"client\"(id,nom,prenom,adr,ville,pass) values(:id,:nom,:prenom,:adr,:ville,:pass)";
            //La valeur DEFAULT parce que la propriété id est auto incrémenté
            MyCnx.Open();
            MyCmd = new NpgsqlCommand(insert, MyCnx);

            //Définition  et ajout des paramètres 

            MyCmd.Parameters.Add(new NpgsqlParameter("id", NpgsqlDbType.Varchar)).Value = client.id;
            MyCmd.Parameters.Add(new NpgsqlParameter("nom", NpgsqlDbType.Varchar)).Value = nom;
            MyCmd.Parameters.Add(new NpgsqlParameter("nom", NpgsqlDbType.Varchar)).Value = nom;
            MyCmd.Parameters.Add(new NpgsqlParameter("prenom", NpgsqlDbType.Varchar)).Value = prenom;
            MyCmd.Parameters.Add(new NpgsqlParameter("tel", NpgsqlDbType.Varchar)).Value = tel;
            MyCmd.Parameters.Add(new NpgsqlParameter("adresse", NpgsqlDbType.Varchar)).Value = adresse;

            MyCmd.ExecuteNonQuery(); //Exécution
            MyCnx.Close();
        }

    }
}

<pre>A first chance exception of type 'System.InvalidOperationException' occurred in Npgsql.dll
The thread 'vshost.RunParkingWindow' (0x338) has exited with code 0 (0x0).
The thread '<No Name>' (0x1658) has exited with code 0 (0x0).
The program '[7312] WindowsFormsApplication1.vshost.exe: Program Trace' has exited with code 0 (0x0).
The program '[7312] WindowsFormsApplication1.vshost.exe: Managed (v4.0.30319)' has exited with code 0 (0x0).

var QCViewAllHistValue1 = (from frmlst in cfList
   join viewalllst in QCViewAllBrokerList1
   on new
   {
       val = String.IsNullOrEmpty(frmlst.Section) ? "" : frmlst.Section.Trim().ToUpper(),
       val1 = String.IsNullOrEmpty(frmlst.xFundCode) ? "" : frmlst.xFundCode.Trim().ToUpper(),
       val2 = String.IsNullOrEmpty(frmlst.Period) ? "" : frmlst.Period.Replace("A", "").Replace("E", "").Trim().ToUpper(),
       val3 = String.IsNullOrEmpty(frmlst.Broker) ? "" : frmlst.Broker.Trim().ToUpper()
   }
   equals new
   {
       val = String.IsNullOrEmpty(viewalllst.ViewAllSection) ? "" : viewalllst.ViewAllSection.Trim().ToUpper(),
       val1 = String.IsNullOrEmpty(viewalllst.xFundCode) ? "" : viewalllst.xFundCode.Trim().ToUpper(),
       val2 = String.IsNullOrEmpty(viewalllst.ViewAllPeriod) ? "" : viewalllst.ViewAllPeriod.Replace("A", "").Replace("E", "").Trim().ToUpper(),
       val3 = String.IsNullOrEmpty(viewalllst.ViewAllBroker) ? "" : viewalllst.ViewAllBroker.Trim().ToUpper()
   }

   select new QCHelper()
   {
       Value = viewalllst == null ? string.Empty : (viewalllst.Value == null ? string.Empty : viewalllst.Value),
   }).ToList<QCHelper>();