C＃和SQL Server中的连接字符串错误

Question

I have fixed the connection string, so it give me errors show here:

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)

The password in microsoft SQL Server has worked also, and in service.msc MSSQLSERVER is running, but Visual Studio shows errors.

This is my code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.Sql;
using System.Data.SqlClient;

namespace Learn_App_Login
{
    public partial class Form1 : Form
    {
        //khai bao bien
        private SqlConnection InitCon;
        private SqlCommand cmd;

        public Form1()
        {
            InitializeComponent();
        }

        //ham ket noi database 
        public static SqlConnection GetCon()
        {
            string strcon = @"data source=LAPTOP-AFR31CFM.;
            initial catalog ='SaleDB';
            user id='LAPTOP-AFR31CFM\D4RKDR4G0N'; password='12@#!';
            Integrated Security=true;";
            SqlConnection con = new SqlConnection(strcon);
            return con;
        }

        private void button1_Click(object sender, EventArgs e)
        {      
            SqlConnection connectionToServer = new SqlConnection();

            SqlConnection con = GetCon();
            con.Open();

            string sqlSelect = "select * from account" +
                               "Where username ='" + txtUsername.Text + "' and password ='" + txtPassword.Text + " ' ";

            // khoi tao doi tuong command
            cmd = new SqlCommand(sqlSelect,con);
            cmd.CommandType = CommandType.Text;

            //khoi tao doi tuong adapter
            SqlDataAdapter adapter = new SqlDataAdapter(cmd);

            //tao datable chua data
            DataTable dt = new DataTable();

            //su dung adapter do data vao table nay
            adapter.Fill(dt);

            //binding eridview voi table
            dgwAccount.DataSource = dt;
        }
    }
}

Answer 1

Look at the error. It says that your database doesn't exist.

Or for some reason the computer the code was running on could not communicate with the SQL Server. This could be caused by a lot of things: Firewall issues, DNS/Name resolution, SQL Configuration (not configured to accept TCP/IP connection)