how to connect database in asp.net

For usability, and ease of editing, store your connection settings to DB in WebConfig of the site like such:

<connectionStrings>
<add name="customNameForConnection" connectionString="Data Source=nameOfServer or IP;Initial Catalog=nameOfTable;Persist Security Info=True;User ID=Login;Password=Password" />
</connectionStrings>

using System.Data.SqlClient;
 lang="c#">public partial class ClassFile: System.Web.UI.Page
{
    SqlConnection con =new SqlConnection(ConfigurationManager.ConnectionStrings["customCon"].ConnectionString);
    using(con){
            //using statement means the connection to DB will be closed once finished, meaning doesn't cause memory leaks.
        con.Open();
        string commandText = "SELECT * from DB";
        using (SqlCommand command = new SqlCommand(commandText, con))
        {
            using (SqlDataReader dataReader = command.ExecuteReader())
            {
               if(dataReader.Read())
               {
                  //read data
               }
            }
        }
    }
}

if you have a DB query with conditions, you can use commandParameters to utilise changing variables in the commandString variable like so:

var commandString = "SELECT * FROM DB where b = @id";

and then in then inside the usingSqlCommand brackets you would add the code:

command.Parameters.Add("@id", SqlDbType.Int).Value = nameOfVariable;

Note you can have multiple commandParameters.

hope this gives you help you need in connecting to SQL

Since this is ASP.NET, you need to mention the framework you're using, if you're using a Web Pages web site then you're going to use the following code to connect to the database.

Database.Open("databaseName"); // connected to databaseName

For more on the above class and the methods, please read this MSDN document[^].

Secondly, if you're using any other method, you can simply just use the SqlClient namespace. That exposes the methods and functions that you can use to connect to the database and perform different operations on it. Since it is a Visual C# code, you can use it in ASP.NET application too. All you need to worry about here is the connectionString for your database, because they need to be precise otherwise the database won't be connected to. For more on connectionStrings, please visit this website. http://connectionstrings.com[^]. The sample code for this one would be,

using (SqlConnection conn = new SqlConnection("{connectionString}")) {
   conn.Open(); // connection opened to the database at the connectionString
   // perform operations here.
}

Read this article[^] for more on connecting to a database through a SqlClient namespace. It would work with any ASP.NET application too.

Same Question , Answerd by many..
see here..
how to access sql database in asp.net[^]

using System.Data.SqlClient;
//Namespace

public partial class _Default : System.Web.UI.Page
{
SqlConnection con=new SqlConnection("server=.;uid=sa;pwd=admin;database=test");

// Server uid and pwd need to change according to your sql server login details

Sql Command cmd=new SqlCommand();
}