using(SqlConnection sc = new SqlConnection()) 
{
  sc.ConnectionString = "Data Source=localhost;Initial Catalog=LoginScreen;Integrated Security=True";
  sc.Open();
using (SqlCommand myCommand = new SqlCommand(
    "INSERT INTO table (rollno, name,feedback) VALUES (@rollno, @name,@feedback)"))
    {
 
    myCommand.Parameters.AddWithValue("@rollno", '"+ txtboxrollnumber.Text +"');
    myCommand.Parameters.AddWithValue("@name", '"+ txtboxname.Text +"');
      myCommand.Parameters.AddWithValue("@feedback", '"+ txtboxfeedback.Text +"');
    //...

   
    myCommand.ExecuteNonQuery();
    //...
    }
sc.Close():
}

http://***.com/questions/16215995/adding-textbox-values-to-an-sql-database-in-c-sharp[^]
:-)

Instead of calling query from asp.net you can write stored procedure for inserting,

CREATE PROCEDURE [dbo].[ADD_Data]
/*Type should be their column types from table*/
@Name varchar(MAX),
@RollNo varchar(MAX),
@Feedback varchar(MAX)
AS
BEGIN
INSERT INTO [dbo].[FeedBackTable] (Name , RollNo , Feedback )
VALUES (@Name , @RollNo , @Feedback )
END


Now below code will go in your Button click ,

protected void Button1_Click(object sender, EventArgs e)
    {
if (Request.QueryString["Name"] != null && Request.QueryString["RollNumber"] != null)
{
 SqlConnection con = new SqlConnection(connectionString);
 SqlCommand com = new SqlCommand("ADD_Data", con);
 com.Parameters.AddWithValue("@Name", Request.QueryString["Name"].ToString());
 com.Parameters.AddWithValue("@RollNo", Request.QueryString["RollNumber"].ToString());
 com.Parameters.AddWithValue("@Feedback", txtboxFeedback.Text);
 com.CommandType = CommandType.StoredProcedure;
 try
 {
    con.Open();
    com.ExecuteNonQuery();
 }
 catch (Exception)
 {
    throw;
 }
 finally
 {
    if (con.State == ConnectionState.Open)
        con.Close();
 }
}
}