Making code duplication to refresh the gridview in asp.net - asp.net

Question

I am trying to update the gridview after updating some data. Here is my code:
protected void Page_Load(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection();
con.ConnectionString = University.GetConnectionString();
con.Open();
string query = "select [ID],[Name],[Surname],[level] from StudentTable order by ID";
SqlCommand cmd = new SqlCommand(query, con);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
studentLevel.DataSource = dt;
studentLevel.DataBind();
con.Close();
}
protected void studentLevel_RowCommand(object sender, GridViewCommandEventArgs e)
{
int row = -1;
int.TryParse(e.CommandArgument as string, out row);
GridViewRow gdrow = studentLevel.Rows[row];
DataRow dr = ((DataTable)studentLevel.DataSource).Rows[gdrow.DataItemIndex];
string id = dr["ID"].ToString();
Student student = new Student(Convert.ToInt32(id), "", "", "", "", "", "", "");
if (e.CommandName == "Undergraduate")
student.setLevelRole(new UnderGraduateStudent());
else if (e.CommandName == "Graduate")
student.setLevelRole(new GraduateStudent());
student.writeLevelRole(id);
SqlConnection con = new SqlConnection(); //HERE IS DUPLICATION
//refresh the gridview on the page
con.ConnectionString = University.GetConnectionString();
con.Open();
string query = "select [ID],[Name],[Surname],[level] from StudentTable order by ID";
SqlCommand cmd = new SqlCommand(query, con);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
studentLevel.DataSource = dt;
studentLevel.DataBind();
con.Close();
}
The problem is, if i do not write the last 12 lines of the code, which is the same code as page_load method, the gridview does not refresh itself on the page. Waht can i do to avoid this?
Thanks

Answer 1

You should provide a method that loads the data and databinds the GridView, for example DataBindGrid:
private void DataBindGrid()
{
using(var con = new SqlConnection(University.GetConnectionString()))
{
con.Open();
string query = "select [ID],[Name],[Surname],[level] from StudentTable order by ID";
SqlCommand cmd = new SqlCommand(query, con);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
studentLevel.DataSource = dt;
studentLevel.DataBind();
}
}
Then you can call it from wherever you need. If you want to change something you have only one place to maintain which is less error-prone.
Note that you should databind the GridView only if(!IsPostBack) if you use ViewState(default):
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostback))
DataBindGridView();
}
and in RowCommand
protected void studentLevel_RowCommand(object sender, GridViewCommandEventArgs e)
{
// ... update student ... then
DataBindGridView();
}