Linq Windows窗体C＃System.Data.SqlClient.SqlException

Question

I'm a student doing an assignment which is an appointment system, I'm using Management Studio for the database, I detached it and linked Visual Studio with the .mdf file.

I can't find where the error is and never solved this type of error before.

Code:

DataClasses1DataContext db = new DataClasses1DataContext();
        public frmAccountCreation()
        {
            InitializeComponent();
        }
    private void btnCreateAccount_Click(object sender, EventArgs e)
    {
        string email = txtEmail.ToString();
        string fullname = txtFullname.ToString();
        string username = txtUsername.ToString();
        string password = txtPassword.ToString();
        int userlevel;
        string contactnumber =txtContactNumber.ToString();
        if(ckbAdmin.Checked)
        {
            userlevel = 1;
        }
        else
        {
            userlevel = 0;
        }

        tblUserAccount account = new tblUserAccount
        {
            Username = username,
            Passcode = password,
            UserPrivelage = userlevel
        };

        tblVet vet = new tblVet
        {
            Email = email,
            FullName = fullname,
            ContactNumber = contactnumber
        };

        db.tblUserAccounts.InsertOnSubmit(account);
        db.tblVets.InsertOnSubmit(vet);
        db.SubmitChanges();//Error Is here
    }
}

Error:

An unhandled exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.Linq.dll

Additional information: 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

Answer 1

Looking at this line:

DataClasses1DataContext db = new DataClasses1DataContext("C:\\Users\\Luke\\Desktop\\OOP Assignment\\OOP_Database.mdf");

You are trying to open the MDF file directly. You cannot do that. You need a running SQL server instance (which can be on your development machine, like SQL Express), and you will need a connection string to connect to that server.

Answer 2

重新安装一切后，我通过卸载与Visual Studio Community 2015和防病毒软件有关的所有内容解决了该问题

Answer 3

It seems your SQL Server Service is not running.

In Windows, search for "Services" and there should be a Windows application with the same name.

In the application keep scrolling untill you find "SQL Server (MSSQLSERVER)" and make sure it's running.