Code for connecting to SQLServer

Question

Dear All,

What is wrong with the following code? The source code was put below in accordance with a picture showing the red lines.

TIA

using System;  
using System.Data;  
using System.Data.SqlClient;  
  
namespace ConnectSql  
{  
    class Program  
    {  
        static void Main(string[] args)  
        {  
            ConnSql.Connect_Sql();  
            Console.WriteLine("Hello World!");  
        }  
    }  
  
    class ConnSql  
    {  
        public void Connect_Sql ()  
        {  
            SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=WelkinDB;Integrated Security=True");  
            SqlCommand cmd;  
            DataTable dt;  
            SqlDataAdapter da;  
            con.Open();  
            cmd = new SqlCommand("Select * from student", con);  
            da = new SqlDataAdapter(cmd);  
            ds = new DataSet();  
            da.Fill(ds, "testTable");  
            con.Close();  
            dt = ds.Tables["testTable"];  
        }  
    }  
}  

Answer 1

Try adding some static:

static class ConnSql
{
   public static void Connect_Sql( )
   {
       . . .
   }
}

Also add a reference to System.Data assembly (in case of .NET Framework) or System.Data.SqlClient package (using "Manage NuGet Packages" command in .NET 5 or Core).

Answer 2

Viorel, thanks for your reply.

Answer 3

1. Ensure that you're able to ping the IP on which the SQL Server database has been set up
2. Please ensure your connection string is something like

<connectionStrings>
<add name="conn2" connectionString="Data Source=192.168.?.?\your_db_instance;Initial Catalog=your_db_schema;Integrated Security=False;User ID=your_db_login;Password=??????" providerName="System.Data.SqlClient"/>
</connectionStrings>

within Web.config/app.config file in your project, to ensure the project will work fine with the database.

Answer 4

Hi Jackson. Thanks for your reply.