如何使用实体模型从数据库保存和检索数据

protected void btnsubmit_Click(object sender, EventArgs e)
{
    dbdataEntities1 dbsdemo = new dbdataEntities1();
    string fname = txtname.Text;
    string lname = txtlastname.Text;
    string email = txtemail.Text;
    string gender = Rbgender.SelectedValue;
    string phoneno = txtphno.Text;
    string role = DropDownList1.SelectedValue;
    string filename = System.IO.Path.GetFileName(Fupload.FileName);
    Fupload.SaveAs(Server.MapPath("Uploads/") + filename);
    tbldata tab = new tbldata();
    tab.filename = filename;
    tab.firstname = fname;
    tab.lastname= lname;
    tab.email = email;
    tab.gender = gender;
    tab.phoneno = Convert.ToInt32(phoneno);
    tab.role = role;
    dbsdemo.tbldatas.Add(tab);
    dbsdemo.SaveChanges();
}

//View.aspx.cs

protected void Page_Load(object sender, EventArgs e)
{
    SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\Napster\documents\visual studio 2015\Projects\WebApplication1\WebApplication1\App_Data\dbdata.mdf;Integrated Security=True;MultipleActiveResultSets=True;Application Name=EntityFramework");
    SqlCommand cmd = new SqlCommand("Select * from tbldata",con);
    SqlDataAdapter adapter = new SqlDataAdapter(cmd);
    DataSet ds = new DataSet();
    adapter.Fill(ds);
    GridView1.DataSource = ds;
    //dbdataEntities1 dbsdemo = new dbdataEntities1();
    // DataSet query = new DataSet();
    // query=    (from tb in dbsdemo.tbldatas select tb).ToList();
    //GridView1.DataSource = dbsdemo.tbldatas.ToList();
    GridView1.DataBind();
}

//view.ASPX
<asp:ImageField DataImageUrlField="filename" DataImageUrlFormatString="~\Uploads\{0}" HeaderText="Photo" ControlStyle-Height="100" ControlStyle-Width="100" >
    <ControlStyle Height="100px" Width="100px"></ControlStyle>
</asp:ImageField>
    <asp:HyperLinkField DataNavigateUrlFields="id" DataNavigateUrlFormatString="update.aspx?id={0}" DataTextField="id" DataTextFormatString="Edit" HeaderText="Edit" Text="Edit" />
</Columns>
protected void btnsubmit_Click(object sender, E