how to connect database in asp.net?

SqlConnection connection = new SqlConnection();
    SqlCommand command = new SqlCommand();
 
    connection.ConnectionString = @"Data Source=.\SQLEXPRESS;" +
        "Initial Catalog=University;Integrated Security=SSPI";
    command.Connection = connection;
    command.CommandText = "INSERT INTO Employees " +
        "(FirstName) VALUES " +
        "(@FirstName)";
 
    command.Parameters.AddWithValue("@FirstName", firstNameTextBox.Text);
     try
    {
        connection.Open();
      command.ExecuteNonQuery();
     
    }
    catch (SqlException ex)
    {
     
    }
    finally
    {
        connection.Close();
    }

Add Textbox and button in the webform.Copy the above code into button_clickEvent.Employee table should be there in your database.