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App_Code and Need Help

Posted on 2007-12-06
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Last Modified: 2013-12-16
Hi,

I am new to ASP.NET.

I have created App_Code folder and placed a class file. Then, I am trying to call it from my site.master.cs.. How do I do that?
my class file called - DSClass.css

namespace DSClassNameSpace
{
    public class DSClass : System.Web.UI.Page
    {
        public DSClass()
        {
        }
        public OleDbDataReader Select_BookIDs()
        {
            OleDbConnection DBConnection = new OleDbConnection(ConfigurationManager.ConnectionStrings["AM"].ConnectionString); ;
            OleDbDataReader DBReader; // read the output
            string SQLString; // to store the sql statements
            DBConnection.Open(); // connection opened
            SQLString = "SELECT DISTINCT PayYear FROM TblPayPeriods";
            OleDbCommand DBCommand = new OleDbCommand(SQLString, DBConnection);
            DBReader = DBCommand.ExecuteReader();
            return DBReader;
            DBReader.Close();
            DBConnection.Close();
        }
    }
}
0
Comment
Question by:neonlights
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9 Comments
 
LVL 27

Expert Comment

by:Sammy
ID: 20421710
you have to use the namespace
using DSClassNameSpace; should be placed after all using statements

then anywhere in the page cs file you can do
private OleDbDataReader mydbReader = Select_BookIDs();

if(mydbReader!=null)
{
//use reader here

}
0
 
LVL 29

Accepted Solution

by:
Göran Andersson earned 2000 total points
ID: 20421758
In the declaration of your page, change System.Web.UI.Page to DSClassNameSpace.DSClass.

In the code:

OleDbDataReader reader = this.Select_BookIDs();

However, you will notice that the reader that you get from the method is rather useless. The database connection has to be open while you read from the data reader.

I suggest that you put an Open and Close method in the class and store the database connection and reader as member variables. Something like:
namespace DSClassNameSpace {
 
    public class DSClass : System.Web.UI.Page {
 
        private OleDbConnection DBConnection;
        private OleDbDataReader DBReader;
 
        public DSClass() {
        }
 
        public void DbOpen() {
            DBConnection = new OleDbConnection(ConfigurationManager.ConnectionStrings["AM"].ConnectionString); ;
            DBConnection.Open(); // connection opened
        }
 
        public void DbClose() {
            DBReader.Close();
            DBConnection.Close();
        }
 
        public OleDbDataReader Select_BookIDs()
        {
            string SQLString; // to store the sql statements
            SQLString = "SELECT DISTINCT PayYear FROM TblPayPeriods";
            OleDbCommand DBCommand = new OleDbCommand(SQLString, DBConnection);
            DBReader = DBCommand.ExecuteReader();
            return DBReader;
        }
    }
}
 
Usage:
 
this.DbOpen();
OleDbDataReader reader = this.Select_BookIDs();
// use the reader here...
this.DbClose();

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0
 

Author Comment

by:neonlights
ID: 20422321
Thanks Sammy and GreenGhost.

Just one question: From Sammy's method - I can declare many different classess.. right?

because, if I use In the declaration of your page, change System.Web.UI.Page to DSClassNameSpace.DSClass, I can only call one class..?

Thanks again.
0
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LVL 27

Expert Comment

by:Sammy
ID: 20422384
Yes you can declare as many classes as you want within the namespace
0
 

Author Comment

by:neonlights
ID: 20422700
Hi GreenGhost.. Sammy,

one bug:

I am using GreenGhost method -

<%@ Master Language="C#" AutoEventWireup="true" CodeBehind="site.master.cs" Inherits="Mine.site" %>
getting error message saying that
'Mine.site' is not allowed here because it does not extend class 'System.Web.UI.MasterPage'.

My aspx.cs has:

namespace Mine
{
    public partial class site : DSClassNameSpace.DSClass
0
 
LVL 29

Expert Comment

by:Göran Andersson
ID: 20422760
> Just one question: From Sammy's method - I can declare many different classess.. right?

Well, Sammys method doesn't work at all. You can't call a method in a class without an instance of the class.


You have inherited the System.Web.UI.Page class in your class. That is done when you use the class as a base for your aspx page class. A page class can only inherit one base class.

If you don't want to use the class as a base class for your page, you shouldn't inherit the System.Web.UI.Page class. Then you also have to create an instance of the class to use it:

DSClass ds = new DSClass();
OleDbDataReader reader = ds.Select_BookIDs();


A namespace can contain as many classes you like, and each class can contain as many methods you like.
0
 

Author Comment

by:neonlights
ID: 20423146
Thanks GreenGhost.. that was very useful.

Do you see Select_BookIDs - this is for a combo box. to fill my combo box.

This is what I have:

in my form_load:

                            ds.DbOpen();
                            OleDbDataReader reader = ds.Select_PayYears();
                            DropDownList1.DataSource = reader;
                            ds.DbClose();

and class code same as before.. how come it is not working.. my dropdown is empty.
0
 
LVL 29

Expert Comment

by:Göran Andersson
ID: 20423187
Settings the data source does not read the data from it. Call the DataBind method:

ds.DbOpen();
OleDbDataReader reader = ds.Select_PayYears();
DropDownList1.DataSource = reader;
DropDownList1.DataBind();
ds.DbClose();
0
 

Author Comment

by:neonlights
ID: 20423392
Thank you GreenGhost.. nice name...

It is working finally.. there was a one mistake in my code..

forgot to add before binding:                            

DropDownList1.DataTextField = "PayYear";
DropDownList1.DataValueField = "PayYear";

Thank you very much for your help and liked the idea of having DbOpen() and DbClose() separate...

Thanks again
0

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