在ASP.NET Web应用程序中重用代码和变量（C＃初学者）

Question

Ive created a webapp in VS2012. The purpose of the app is to update data that is shown on different displays throuhout the company. Each display has it's own data to be shown. All data is stored in a single SQL table and has a specific column to know what data has to be shown on what display. The webapp consist op different aspx pages to update the data on the different screens, so I have UpdateScreen1.aspx, UpdateScreen2.aspx, ... The core of these pages is about 90% the same. They start with a SQL connection, get a list of data for this specific screen (so, the SQL statement is the same except for the WHERE clause), and of course the create/update/delete functions for the data. If I need to change for example my select statement I have to update all the pages. Also the SQL connection is specified in each page seperately. I was wondering if I could make this a bit more performant, by re-using for example the select statement (defining it once, and adding only the where clause in the specific page), the sql connection, ... However I can't seem to find where to put them. I've already tried global.asax, a seperate class file, ... but nothing seems to work (name xxxxx does not exists in current context...).

Here some of my code: UpdateScreen1.aspx:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;

namespace RSS_Aankondigingen.UpdateScreen1
{
    public partial class Update_Announcement : System.Web.UI.Page
    {
        private SqlConnection sqlConn = new SqlConnection("Data Source=server;Initial Catalog=db;Persist Security Info=True;User ID=user;Password=password");

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                gvBind();
            }
        }

        protected void gvBind()
        {
            sqlConn.Open();
            string a = sqlSelect;

            SqlCommand sqlCmd = new SqlCommand("SELECT ID, Title,  CONCAT(CONVERT(char(16), Date, 103),CONVERT(char(5), Date, 108)) AS Date, Recurrent FROM tblAnnouncements WHERE Channel = 'SH_ANN' ORDER BY Date", sqlConn);
            SqlDataAdapter sqlDA = new SqlDataAdapter(sqlCmd);
            DataSet ds = new DataSet();
            sqlDA.Fill(ds);
            sqlConn.Close();
            if (ds.Tables[0].Rows.Count > 0)
            {
                GridAnnouncements.DataSource = ds;
                GridAnnouncements.DataBind();
            }
            else
            {
                ds.Tables[0].Rows.Add(ds.Tables[0].NewRow());
                GridAnnouncements.DataSource = ds;
                GridAnnouncements.DataBind();
                int colCount = GridAnnouncements.Rows[0].Cells.Count;
                GridAnnouncements.Rows[0].Cells.Clear();
                GridAnnouncements.Rows[0].Cells.Add(new TableCell());
                GridAnnouncements.Rows[0].Cells[0].ColumnSpan = colCount;
                GridAnnouncements.Rows[0].Cells[0].Text = "Geen gegevens gevonden...";
            }

        }
    }
}

Any help would be very much appreciated.

Michiel.

EDIT: uncommented sqlConn initiatlization (it was for testing)

Answer 1

If you're using ADO, then you could use Stored Procedures with parameters, then your SqlCommand becomes the name of the stored procedure (change CommandType to StoredProcedure) and just add parameters to the command.

However, also look into more modern options like Entity Framework and you would use Linq against a collection of Announcement objects.

Answer 2

to answer your Question, create another class, and use it to wrap the sql code. (This is all from memory, so if theres mistakes, apologies.)

ie

namespace RSS_Aankondigingen

public class DatbaseHelper
{

public DataSet GetDataSet(string selectOn)
{
        sqlConn.Open();

string sqlQuery = string.format("SELECT ID, Title,  CONCAT(CONVERT(char(16), Date, 103),CONVERT(char(5), Date, 108)) AS Date, Recurrent FROM tblAnnouncements WHERE Channel = '{0}' ORDER BY Date", selectOn);


        SqlCommand sqlCmd = new SqlCommand(sqlQuery, sqlConn);
        SqlDataAdapter sqlDA = new SqlDataAdapter(sqlCmd);
        DataSet ds = new DataSet();
        sqlDA.Fill(ds);
        sqlConn.Close();

        return ds;
}
}

then in your code, when you need to do a select;

replace all the code that is above with. (Where SH_ANN is whatever you wish to select on for that page.)

DataSet ds = GetDataSet("SH_ANN");

This is not an optimal solution, but as a first step, it will let you isolate the SQL code into a single class, to make maintenance easier.