Question

net to adding database. I am trying to do texts on two textbox and one selected value in dropdownlist to add my table.
Here is my code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;

public partial class _Default : System.Web.UI.Page

{

    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        string connectionString = @" Data Source=.\SQLEXPRESS;AttachDbFilename=C:\USERS\CEM\DOCUMENTS\VISUAL STUDIO 2010\WEBSITES\EKLEMEDENE\APP_DATA\DATABASE.MDF;Integrated Security=True;User Instance=True";
        string queryString = "INSERT INTO ekle(flight, name, food) VALUES   ('" + TextBox1.Text + " ' , '" + TextBox2.Text + " ' ,  '" + DropDownList1.SelectedValue + " '  )";
        SqlConnection con = new SqlConnection(connectionString);
        SqlCommand command = new SqlCommand(queryString, con);
        con.Open();
        command.ExecuteNonQuery();

        con.Close();
    }
}

After I execute I will have error

Database ‘C:\Users\Cem\Documents\Visual Studio 2010\WebSites\eklemedene\App_Data\Database.mdf’ already exists. Choose a different database name.
An attempt to attach an auto-named database for file C:\USERS\CEM\DOCUMENTS\VISUAL STUDIO 2010\WEBSITES\EKLEMEDENE\APP_DATA\DATABASE.MDF failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share.

Answer 1

1. You’re wide open for SQL-Injection. Avoid passing parameters directly from controls. Instead use Parameters.
2. Use using-statement for anything implementing IDisposable like Connections or Commands:
3. There’s something wrong with your ConnectionString, you could try to use SqlConnectionStringBuilder class:

---

//Build the connection 
SqlConnectionStringBuilder bldr = new SqlConnectionStringBuilder();

//Put your server or server\instance name here.  Likely YourComputerName\SQLExpress
bldr.DataSource = ".\\SQLEXPRESS";

//Attach DB Filename
bldr.AttachDBFilename = @"C:\USERS\CEM\DOCUMENTS\VISUAL STUDIO 2010\WEBSITES\EKLEMEDENE\APP_DATA\DATABASE.MDF";

//User Instance
bldr.UserInstance = true;

//Whether or not a password is required.
bldr.IntegratedSecurity = true;

using(var connection = new SqlConnection(bldr.ConnectionString))
{
    var sql = "INSERT INTO ekle(flight, name, food) VALUES (@flight, @name , @food)";
    using(var command = new SqlCommand(sql, connection))
    {
        command.Parameters.AddWithValue("@flight", TextBox1.Text);
        command.Parameters.AddWithValue("@name", TextBox2.Text);
        command.Parameters.AddWithValue("@food", DropDownList1.SelectedValue); 
        connection.Open();
        command.ExecuteNonQuery();
    }
} // closes the connection implicitely