I am not sure what the problem is here, so I am reaching out. I have an interfaced DataLayer class which recalls some customer data I am using to fill a gridview. I dependency inject this directly into a winform partial class (I am skipping the BusinessLayer for now). I am newer to Winforms so maybe there is something I am not seeing here or maybe I am being dense in my code.

Interface:

namespace DL
{
    public interface IRepo<T>
    {
        List<T> GetAll();
    }
}

DataLayer

namespace DL
{
    public class CustomersRepo : IRepo<Customers>
    {
        string constring = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
        
        public List<Customers> GetAll()
        {
            List<Customers> customers = new List<Customers>();
            string sqlQuery =@"SELECT * FROM CUSTOMERS";

            using (SqlConnection con = new SqlConnection(constring))
            {
                con.Open();
                SqlCommand command = new SqlCommand(sqlQuery, con);
                SqlDataReader reader = command.ExecuteReader();
                while (reader.Read())
                {
                    Customers customer = new Customers();
                    customer.CustomerID = reader.GetInt32(0);
                    customer.LastName = reader.GetString(1);
                    customer.FirstName = reader.GetString(2);
                    customer.Address = reader.GetString(3);
                    customer.City = reader.GetString(4);
                    customers.Add(customer);
                }
            }
            return customers;
        }
    }
}

Dependency Injection:

    public partial class Main : Form
    {
        public List<Customers> CustomersData { get; set; }

        private IRepo<Customers> _repo;
        public Main(IRepo<Customers> repo)
        {
            _repo = repo;
        }

Main:

        public Main()
        {
            CustomersData = _repo.GetAll();
            InitializeComponent();
        }

Form Load:

        private void Main_Load(object sender, EventArgs e)
        {
            dataGridViewCust.DataSource = CustomersData;
        }

If I insert this Datalayer method directly into the form class, everything works fine. I am trying to keep to some of the design principles I learned in a recent bootcamp, and hence was trying to separate the concerns visa via dependency injection. Am I being stupid somewhere? I've looked at other examples of the similar null question on here but have not found where my problem is... Any help or advice would be appreciated. I feel like I have majorly overlooked something.

EDIT: (I've tried directly inserting the repo class as well without the IRepo abstraction.)

CodePudding user response：

You should do dependency injection in program.cs. For this, install the autofac package and write the sample codes below.

using Autofac;
using System;
using System.Windows.Forms;

namespace WindowsFormsApp1
{
    internal static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1(Container.Resolve< IRepo>()));
        }

        static IContainer Configure()
        {
            var builder = new ContainerBuilder();
            builder.RegisterType<CustomersRepo>().As<IRepo>();
            builder.RegisterType<Form1>();
            return builder.Build();
        }
    }
 }

CodePudding user response：

There are several good answers on SO (e.g.

Since the DataGridView needs to respond to subsequent queries, it needs a DataSource that will notify it of changes to the customers list as they occur. In this example, I have changed List<Customer> to BindingList<Customer> and initialized it in the override for the Load event of the Main form.

/// <summary>
/// A binding list will notify DGV when data changes
/// </summary>
public BindingList<Customer> Customers { get; } = new BindingList<Customer>();
protected override void onl oad(EventArgs e)
{
    base.OnLoad(e);
    dataGridViewCust.DataSource = Customers;

    // Here we're calling a method that simulates the
    // sql query by returning a fake list of customers
    foreach (var customer in _repo.GetAllMock())
    {
        Customers.Add(customer);
    }
    foreach (DataGridViewColumn column in dataGridViewCust.Columns)
    {
        column.AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill;
    }
}

Working with BindingList

You probably noticed that the BindingList was declared as a read-only property. When a new query is performed, simply perform a Clear on it before adding the new records.

private void changeTheBindingListExample()
{
    Customers.Clear();

    foreach (
        var customer in 
        _repo.NewQueryMock("SELECT * FROM CUSTOMERS WHERE FirstName='Other'"))
    {
        Customers.Add(customer);
    }
}