This code defines a class that connects to a SQL database to perform CRUD operations on a student details table. It opens a connection, populates a dropdown with student IDs from the table. It allows updating, inserting, deleting and retrieving a student's details by ID, and displays the results in a grid view. Buttons trigger methods for each database operation like update, insert, delete, retrieve.

1. public partial class _Default : System.Web.UI.Page
{ SqlConnection con=new SqlConnection("Data Source=kol-11102-srvmr; Initial
Catalog=Student_s1; User ID = sa; Password = niit@123");
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
Student_Detail();
}
public void Student_Detail()
{
con.Open();
SqlCommand cmd = new SqlCommand("select Student_Id from Student_Detail
", con);
SqlDataAdapter ad = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
ad.Fill(dt);
DropDownList1.Items.Clear();
DropDownList1.DataSource = dt;
DropDownList1.DataTextField = "Student_Id";
DropDownList1.DataBind();
}
protected void Button1_Click(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection();
con.ConnectionString = "Data Source=kol-11102-srvmr; Initial
Catalog=Student_s1; User ID = sa; Password = niit@123";
con.Open();
SqlCommand cmd = new SqlCommand("update Student_Detail set
S_Name='"+TextBox1.Text+"',Course='"+TextBox2.Text+"',Address='"+TextBox3.Text+"
',Phon_no='"+TextBox4.Text+"' where Student_Id='"+DropDownList1.Text+"'",con);
cmd.ExecuteNonQuery();
}
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs
e)
{
SqlConnection con = new SqlConnection();
con.ConnectionString = "Data Source=kol-11102-srvmr; Initial
Catalog=Student_s1; User ID = sa; Password = niit@123";
con.Open();
SqlCommand cmd = new SqlCommand("select* from Student_Detail where
Student_Id ='" + DropDownList1.Text + "'", con);
SqlDataReader dr = cmd.ExecuteReader();
dr.Read();
if (dr.HasRows)
{
TextBox5.Text = dr["Student_Id"].ToString();
TextBox1.Text= dr["S_Name"].ToString();
TextBox2.Text= dr["Course"].ToString();
TextBox3.Text= dr["Address"].ToString();
TextBox4.Text = dr["Phon_no"].ToString();
}
}
protected void Button2_Click(object sender, EventArgs e)

2. {
SqlConnection con = new SqlConnection();
con.ConnectionString = "Data Source=kol-11102-srvmr; Initial
Catalog=Student_s1; User ID = sa; Password = niit@123";
con.Open();
SqlCommand cmd = new SqlCommand("insert into Student_Detail
values('"+DropDownList1.Text+"','"+TextBox1.Text + "','" + TextBox2.Text + "','"
+ TextBox3.Text + "','" + TextBox4.Text + "')", con);
cmd.ExecuteNonQuery();
TextBox5.Text = "";
TextBox1.Text = "";
TextBox2.Text = "";
TextBox3.Text = "";
TextBox4.Text = "";
}
protected void Button3_Click(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection();
con.ConnectionString = "Data Source=kol-11102-srvmr; Initial
Catalog=Student_s1; User ID = sa; Password = niit@123";
con.Open();
SqlCommand cmd = new SqlCommand("Delete Student_Detail where
Student_Id='" + DropDownList1.Text + "'", con);
cmd.ExecuteNonQuery();
TextBox5.Text = "";
TextBox1.Text = "";
TextBox2.Text = "";
TextBox3.Text = "";
TextBox4.Text = "";
}
protected void Button4_Click(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection();
con.ConnectionString = "Data Source=kol-11102-srvmr; Initial
Catalog=Student_s1; User ID = sa; Password = niit@123";
con.Open();
SqlCommand cmd = new SqlCommand("select * from Student_Detail where
Student_Id='" + DropDownList1.Text + "'", con);
SqlDataAdapter ad = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
ad.Fill(ds);
GridView1.DataSource = ds;
GridView1.DataBind();
TextBox5.Text = "";
TextBox1.Text = "";
TextBox2.Text = "";
TextBox3.Text = "";
TextBox4.Text = "";
}
}