C# | Exception thrown: 'System.IO.FileNotFoundException' in Businesslaag_Class_Libary.dll

Question

I am working to discover how to work with a layered architecture, and I am running into a problem.

This is the code from my data layer:

using System.Data;
using System.Data.SqlClient;

namespace Datalaag_Class_Libary
{
    public class Datalaag_Connectie_Class
    {
        public string ConnectionString = "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=master;Integrated Security=True;Connect Timeout=30;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False";
        SqlConnection con = new SqlConnection();
        DataTable dt = new DataTable();
        public DataTable Read()
        {
            con.ConnectionString = ConnectionString;
            if (ConnectionState.Closed == con.State)
                con.Open();
            SqlCommand cmd = new SqlCommand("select * from demo_wedstrijdschema" , con);
            try
            {
                SqlDataReader rd = cmd.ExecuteReader();
                dt.Load(rd);
                return dt;
            }
            catch
            {
                throw;
            }
        }
    }

    }

This is the code form the business layer:

using System.Data;
using Datalaag_Class_Libary;

namespace Businesslaag_Class_Libary
{
    public class Busines_laag_class
    {
        public DataTable GetInfo()
        {
            try
            {
                Datalaag_Connectie_Class objdal = new Datalaag_Connectie_Class();
                return objdal.Read();
            }
            catch
            {
                throw;
            }
        }

    }
}

And this is the code from the user interface layer:

using System;
using System.Windows.Forms;
using Businesslaag_Class_Libary;

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            try
            {
                Busines_laag_class test = new Busines_laag_class();
                this.dataGridView1.DataSource = test.GetInfo();
            }
            catch
            {
                MessageBox.Show("error");
            }
        }
    }
}

The program can run (not as it should run), but in the output screen the following error occurs: Exception thrown: 'System.IO.FileNotFoundException' in Businesslaag_Class_Libary.dll This is my full output screen: The asked exception output:

Dont know what I have done wrong in the code. Can anyone help? Thanks in advance!

Include (and account for) the _full_ exception, including call stack. — user2864740, May 11 '20 at 17:49
@MartinStaufcik I don't know what you mean with ex.ToString, but thats my whole output window. — Josse, May 11 '20 at 17:58
@user2864740 Is it possible that my call stack is empty, because I checked my call stack, and it is empty, unless I am doing something wrong. — Josse, May 11 '20 at 17:59
for ex.toString you should add these lines of code for your catch part catch (Exception ex) { MessageBox.Show(ex.toString()); } — Ali Kianoor, May 11 '20 at 18:03

score 0 · Answer 1 · answered May 11 '20 at 18:22

0

I think one of your assembly files is missed, which is System Data SqlClient. Try to add this package to your data layer with this command or directly by yourself.

dotnet add package system.data.sqlclient

answered May 11 '20 at 18:22

Ali Kianoor

1,167
9
18

I checked for this in my ManageGetNU packeges, but I have System.Data.SqlClient installed. – Josse May 11 '20 at 18:26
so try to add it in your form or business layer, because the problem is the system can not recognize your system.data.sqlclient reference correctly! – Ali Kianoor May 11 '20 at 18:29

score 0 · Answer 2 · answered May 11 '20 at 18:25

0

You may need to add a reference to System.Data.SqlClient from your WindowsFormsApp1 project. Try adding the same version as is used from the data layer project.

It seems the project of data layer did not copy the assembly System.Data.SqlClient.dll to output folder and there is no 'Copy local' option anymore.

answered May 11 '20 at 18:25

Martin Staufcik

8,295
4
44
63

I cant find the System.Data.SqlClient in my reference Manager. How do I add this? – Josse May 11 '20 at 18:33
go to Tools > NuGet Package Manager > Manage NuGet packages for solution. There type 'System.Data.SqlClient' in 'Browse' tab and check the project WindowsFormsApp1. – Martin Staufcik May 11 '20 at 18:38
It is installed on all 3 the projects, I just checked. – Josse May 11 '20 at 18:40
is the version the same? – Martin Staufcik May 11 '20 at 18:43
The version is on all 3: 4.8.1 – Josse May 11 '20 at 18:45
Are your three projects targetting the same version of .NET? – Martin Staufcik May 11 '20 at 18:46
How do I check that? – Josse May 11 '20 at 18:49
Project properties -> Application -> Target framework – Martin Staufcik May 11 '20 at 18:51
maybe you could try also this https://stackoverflow.com/questions/43837638/how-do-i-get-net-core-projects-to-copy-nuget-references-to-the-build-output – Martin Staufcik May 11 '20 at 18:55
Thanks for trying, but I am stopping for tonight, the projects are all three targetting the same version. But is it normal for this to happen, or is it pretty strange? – Josse May 11 '20 at 18:55
Yes, it is strange. – Martin Staufcik May 11 '20 at 18:56

C# | Exception thrown: 'System.IO.FileNotFoundException' in Businesslaag_Class_Libary.dll

2 Answers2