Connect to SQL Server with C#

Hello Edward,

I think you are missing few things in reference. As Mahesh Chand shared you need to refer "Microsoft.Data.SqlClient" namesapce to connect to sql server. 

Please refer sample code as below,

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;

public class UserDataAccess
{
    private readonly string connectionString = "Your Connection String"; // Replace with your origanla SQL Server connection string

    public List GetAllUsers()
    {
        List users = new List();
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            string sql = "SELECT Id, Name, Email FROM Users"; // Your SQL query
            using (SqlCommand command = new SqlCommand(sql, connection))
            {
                connection.Open();
                SqlDataReader reader = command.ExecuteReader();
                while (reader.Read())
                {
                    users.Add(new User
                    {
                        Id = Convert.ToInt32(reader["Id"]),
                        Name = reader["Name"].ToString(),
                        Email = reader["Email"].ToString(),
                        // Map other columns as required
                    });
                }
                reader.Close();
            }
        }
        return users;
    }
}

What is using OnTarget2019.DataClasses?

Can can use ADO.NET, and for that you must import the correct namespace in your class. 

using Microsoft.Data.SqlClient;

There is much more that you did not say.

I also forgot to say that I did what you suggested before I asked my original question. I know the connection string, it is getting the right syntax and "Usings" to open the connection.

What do you mean by project will open the databases?

What is the code you are using for the database?

In Visual Studio, in the View menu, when you select SQL Server Object Explorer and right-click on the database, select Properties. In the properties is a connection string for the database. I think you can also get a connection string using SQL Server Management Studio (SSMS).