Nullreferenceexception when trying to write to database

Question

I have this error, when I will record the form data in the database.

Error: System.Nullreferenceexception:

System.NullReferenceException ocorrido
  HResult=0x80004003
  Message=Referência de objeto não definida para uma instância de um objeto.
  Source=ProjetoAlpha
  StackTrace:
   em ProjetoAlpha.frmProduto.btnGravar_Click(Object sender, EventArgs e) em C:\Users\willian\source\repos\ProjetoAlpha\ProjetoAlpha\frmProduto.cs:linha 29
   em System.Windows.Forms.Control.OnClick(EventArgs e)
   em System.Windows.Forms.Button.OnClick(EventArgs e)
   em System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   em System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   em System.Windows.Forms.Control.WndProc(Message& m)
   em System.Windows.Forms.ButtonBase.WndProc(Message& m)
   em System.Windows.Forms.Button.WndProc(Message& m)
   em System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   em System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   em System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   em System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   em System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
   em System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   em System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   em System.Windows.Forms.Application.Run(Form mainForm)
   em ProjetoAlpha.Program.Main() em C:\Users\willian\source\repos\ProjetoAlpha\ProjetoAlpha\Program.cs:linha 19

This is the method to insert:

This is my Postgresql table:

This is the full class of connection and methods:

using System;
using Npgsql;
using System.Data;

namespace ProjetoAlpha
{
    class DAL
    {
        static string serverName = "localhost";
        static string port = "5432";
        static string userName = "postgres";
        static string password = "adm";
        static string databaseName = "dbestoque";
        NpgsqlConnection conn = null;
        string ConnString = null;

        public DAL()
        {
            ConnString = String.Format("Server={0};Port={1};User Id{2};Password={3};Database={4};",
                                       serverName, port, userName, password, databaseName);    
        }

        public DataTable GetTodosRegistros()
        {
            DataTable dt = new DataTable();

            try
            {
                using (conn = new NpgsqlConnection(ConnString))
                {
                    conn.Open();
                    string cmdSeleciona = "SELECT * FROM estoque order by id_produto";

                    using (NpgsqlDataAdapter da = new NpgsqlDataAdapter(cmdSeleciona, conn))
                    {
                        da.Fill(dt);
                    }
                }
            }
            catch (NpgsqlException ex)
            {
                throw ex;
            }
            finally
            {
                conn.Close();
            }    
            return dt;
        }

        public DataTable GetRegistroPorId(int id)
        {
            DataTable dt = new DataTable();

            try
            {
                using (NpgsqlConnection conn = new NpgsqlConnection(ConnString))
                {
                    conn.Open();
                    string cmdSeleciona = "SELECT * FROM ESTOQUE WHERE codigo =" + id;

                    using (NpgsqlDataAdapter da = new NpgsqlDataAdapter(cmdSeleciona, conn))
                    {
                        da.Fill(dt);
                    }
                }
            }
            catch (NpgsqlException ex)
            {
                throw ex;
            }
            catch(Exception ex)
            {
                throw ex;
            }
            finally
            {
                conn.Close();
            }

            return dt;
        }

        public void InserirRegistros(string nome, int codigo, int minimo, int maximo, int qtd, DateTime data)
        {
            try
            {
                using (NpgsqlConnection conn = new NpgsqlConnection(ConnString))
                {
                    conn.Open();

                    string cmdInserir = String.Format("INSERT INTO ESTOQUE(nome,codigo,minimo,maximo,quantidade,dataEntrada) " +
                                                                    "VALUES ('{0}','{1}','{2}','{3}','{4}','{5}')", nome, codigo, minimo, maximo, qtd, data);

                    using (NpgsqlCommand cmd = new NpgsqlCommand(cmdInserir, conn))
                    {
                        cmd.ExecuteNonQuery();
                    }
                }
            }catch(NpgsqlException ex)
            {
                throw ex;
            }catch(Exception ex)
            {
                throw ex;
            }
            finally
            {
                conn.Close();
            }
        }
    }
}

Record button:

 private void btnGravar_Click(object sender, EventArgs e)
        {
            DAL acesso = new DAL();

            try
            {
                acesso.InserirRegistros(txtNomeProduto.Text, Convert.ToInt32(txtCodigo.Text), Convert.ToInt32(txtMinimo.Text), Convert.ToInt32(txtMaximo.Text), Convert.ToInt32(txtEntrada.Text), dtpData.Value);
            }catch(Exception ex)
            {
                throw ex;
            }
            finally
            {
                MessageBox.Show("Cadastrado com sucesso!");
            }
        }

I removed the Try, catch and Finally and error in the Insert Data class:

System.ArgumentException ocorrido
  HResult=0x80070057
  Message=Keyword not supported: user idpostgres;password
Parameter name: keyword
  Source=Npgsql
  StackTrace:
   em Npgsql.NpgsqlConnectionStringBuilder.GetProperty(String keyword)
   em Npgsql.NpgsqlConnectionStringBuilder.set_Item(String keyword, Object value)
   em System.Data.Common.DbConnectionStringBuilder.set_ConnectionString(String value)
   em Npgsql.NpgsqlConnectionStringBuilder..ctor(String connectionString)
   em Npgsql.NpgsqlConnection.GetPoolAndSettings()
   em Npgsql.NpgsqlConnection.set_ConnectionString(String value)
   em Npgsql.NpgsqlConnection..ctor(String connectionString)
   em ProjetoAlpha.DAL.InserirRegistros(String nome, Int32 codigo, Int32 minimo, Int32 maximo, Int32 qtd, DateTime data) em C:\Users\willian\source\repos\ProjetoAlpha\ProjetoAlpha\DAL.cs:linha 91
   em ProjetoAlpha.frmProduto.btnGravar_Click(Object sender, EventArgs e) em C:\Users\willian\source\repos\ProjetoAlpha\ProjetoAlpha\frmProduto.cs:linha 26
   em System.Windows.Forms.Control.OnClick(EventArgs e)
   em System.Windows.Forms.Button.OnClick(EventArgs e)
   em System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   em System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   em System.Windows.Forms.Control.WndProc(Message& m)
   em System.Windows.Forms.ButtonBase.WndProc(Message& m)
   em System.Windows.Forms.Button.WndProc(Message& m)
   em System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   em System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   em System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   em System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   em System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
   em System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   em System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   em System.Windows.Forms.Application.Run(Form mainForm)
   em ProjetoAlpha.Program.Main() em C:\Users\willian\source\repos\ProjetoAlpha\ProjetoAlpha\Program.cs:linha 19

Answer 1

nullException error is happening on conn.Close(); because the conn is void. An error occurred while trying to create it.

I believe there’s only one missing = in the syntax in the connection string:

Server={0};Port={1};User Id={2};Password={3};Database={4};