Types of connections in ASP.NET and ADO.NET

1. In App Setting at Webconfig File:

        <appSetting >

            <add key="con" value="Server=admin;database=hms;userid=dileep;pwd=123"/>

        </asssetting>

2. In Connection setting at Webconfig File:

     <connectionStrings>

<add name="con2" connectionString="Initial Catalog=ds;data source=A-61810D2C88704\SQLEXPRESS;integrated                         security=true"/>

<add name="con1" connectionString="Initial Catalog=ds;data source=vishal-hp;integrated security=true;"/>

</connectionStrings>

3. Common Connection(Common Class):

using System;

using System.Data;

using System.Configuration;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.HtmlControls;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Data.SqlClient;

/// <summary>

/// Summary description for DataClass

/// </summary>

public class DataClass

{

    public string strcon;

    public SqlConnection cn;

    public SqlCommand cmd;

   

public DataClass()

{

//

// TODO: Add constructor logic here

         //strcon = "Data Source=RICHA\\SQLEXPRESS;Initial Catalog=NPsilvani;Integrated Security=true;";

        //strcon= "Data Source=.\\SQLEXPRESS;AttachDbFilename=|DataDirectory|\\NPsilvani.mdf;Integrated Security=True";

        //strcon = @"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\NPsilvani.mdf;Integrated Security=true;User                Instance=True";

        //strcon = @"Data Source=111.118.178.5;DataBase=npsilwan_;Integrated Security=true";

        strcon = ConfigurationManager.ConnectionStrings["rupadbConnectionString"].ConnectionString.ToString();

//a

}

    public  void Openconnection()

    {

        cn = new SqlConnection( strcon);

        cn.Open();

    }

    public  void Closeconnection()

    {

        if (cn.State == ConnectionState.Open)

            cn.Close();

    }

    public  void ExecuteCMD(string str)

    {

        Openconnection();

        cmd = new SqlCommand(str, cn);

        cmd.ExecuteNonQuery();

        Closeconnection();

    }

}

4. In Code Behind Page Directly:

    public string strcon;

    public SqlConnection cn;

    public SqlCommand cmd;

   //strcon = "Data Source=RICHA\\SQLEXPRESS;Initial Catalog=NPsilvani;Integrated Security=true;";

    cn.Open();

    and  last

    cn.close();