sqlConnect

Question

Hello all. I'm new in C# and have use always Visual Basic so much different isn't it. I'm try to make an desktop app that connect to my SQL server. I have a good book that guide me. SO I must put using System.Data.sqlClient. I can use sqqlConnection. This works in .net framework. Now I want to go to .net 5.0 and use that same but now het don't recognise my sqlconnection anymore. So if someone can tell me what I must ad as using so I can use sqlconnection again with his function I would be happy. Or best way I stay in .net framework

Answer 1

In order to use SQL client classes, try this method: right-click the project in Solution Explorer, select “Manage NuGet Packages…”, “Browse” tab, type “System.Data.SqlClient”, find and install it. Make sure that your code file contains using System.Data.SqlClient.

Answer 2

Whell it is installed because if I make on same system in visual studio a desktop program with .net framework 4.7 I can use it when I upt in my file cose using System.Data.SqlClient. So it is onmy computer but on .net 5 it is not working that is the strange thing.

Answer 3

Viorel-1 has provided you with what to do to get those classes working via this NuGet package. Here is a code sample that uses new C# features along with a pre-defined time-out if a connection fails.

using System;  
using System.Data;  
  
namespace WorkingWithSqlServer.Classes  
{  
    public class DataTableResults  
    {  
        /// <summary>  
        /// Holds data read from a database.  
        /// </summary>  
        public DataTable DataTable { get; set; }  
        /// <summary>  
        /// Set when there is a connection to the server failure  
        /// </summary>  
        public bool ConnectionFailed { get; set; }  
        /// <summary>  
        /// General exception message  
        /// </summary>  
        public string ExceptionMessage { get; set; }  
        /// <summary>  
        /// General exception if not connection failure  
        /// </summary>  
        public Exception GeneralException { get; set; }  
        /// <summary>  
        /// Is there an exception thrown  
        /// </summary>  
        public bool HasException => ConnectionFailed || GeneralException != null;  
    }  
}  

Data operations

using System;  
using System.Data;  
using System.Data.SqlClient;  
using System.Threading;  
using System.Threading.Tasks;  
  
namespace WorkingWithSqlServer.Classes  
{  
    public class DataOperations  
    {  
        private static string _connectionString =  
            "Data Source=.\\sqlexpress;" +   
            "Initial Catalog=NorthWind2020;" +   
            "Integrated Security=True";  
  
  
        public static async Task<DataTableResults> ReadProductsTask(CancellationToken ct)  
        {  
            var result = new DataTableResults() { DataTable = new DataTable() };  
  
            return await Task.Run(async () =>  
            {  
                await using var cn = new SqlConnection(_connectionString);  
                await using var cmd = new SqlCommand() { Connection = cn };  
                cmd.CommandText = SelectStatement();  
  
                try  
                {  
                    await cn.OpenAsync(ct);  
                }  
                catch (TaskCanceledException tce)  
                {  
                    result.ConnectionFailed = true;  
                    result.ExceptionMessage = "Connection Failed";  
                    return result;  
                }  
                catch (Exception ex)  
                {  
                    result.GeneralException = ex;  
                    return result;  
                }  
  
                result.DataTable.Load(await cmd.ExecuteReaderAsync(ct));  
  
                return result;  
  
            });  
  
        }  
  
        private static string SelectStatement()  
        {  
            return "SELECT P.ProductID, P.ProductName, P.SupplierID, S.CompanyName, P.CategoryID, " +  
                   "C.CategoryName, P.QuantityPerUnit, P.UnitPrice, P.UnitsInStock, P.UnitsOnOrder, " +  
                   "P.ReorderLevel, P.Discontinued, P.DiscontinuedDate " +  
                   "FROM  Products AS P INNER JOIN Categories AS C ON P.CategoryID = C.CategoryID " +  
                   "INNER JOIN Suppliers AS S ON P.SupplierID = S.SupplierID";  
        }  
  
    }  
  
}  

Form code

using System;  
using System.Threading;  
using System.Threading.Tasks;  
using System.Windows.Forms;  
using WorkingWithSqlServer.Classes;  
  
namespace WorkingWithSqlServer  
{  
    public partial class Form1 : Form  
    {  
        private const int TimeOutSeconds = 5;  
        private CancellationTokenSource _cancellationTokenSource = new(TimeSpan.FromSeconds(TimeOutSeconds));  
        public Form1()  
        {  
            InitializeComponent();  
            Shown += OnShown;  
        }  
  
        private async void OnShown(object? sender, EventArgs e)  
        {  
            await LoadData(true);  
        }  
  
        private async Task LoadData(bool firstTime = false)  
        {  
            if (!firstTime)  
            {  
                if (_cancellationTokenSource.IsCancellationRequested)  
                {  
                    _cancellationTokenSource.Dispose();  
                    _cancellationTokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(TimeOutSeconds));  
                }  
            }  
  
            var dataResults = await DataOperations.ReadProductsTask(_cancellationTokenSource.Token);  
  
            if (dataResults.HasException)  
            {  
                MessageBox.Show(dataResults.ConnectionFailed ?   
                    @"Connection failed" :   
                    dataResults.GeneralException.Message);  
            }  
            else  
            {  
                dataGridView1.DataSource = dataResults.DataTable;  
            }  
        }  
    }  
}  

Project file

Double click on the project name in solution explorer, make sure after installing the NuGet package this is what your project file looks like.

<Project Sdk="Microsoft.NET.Sdk">  
  
	<PropertyGroup>  
		<OutputType>WinExe</OutputType>  
		<LangVersion>9.0</LangVersion>  
		<TargetFramework>net5.0-windows</TargetFramework>  
		<UseWindowsForms>true</UseWindowsForms>  
	</PropertyGroup>  
  
	<ItemGroup>  
	  <PackageReference Include="System.Data.SqlClient" Version="4.8.2" />  
	</ItemGroup>  
  
</Project>  

Answer 4

I don't think you can except that a .NET Framework solution prior to 5 is going to work if do not look at the migration of the solution to .Net 5

https://learn.microsoft.com/en-us/dotnet/architecture/modernize-desktop/example-migration