Brownie's Bikes

In Search of the Ultimate Data Access Layer - Summary

Andrew Browne — Sat, 05 Jan 2008 09:43:54 GMT

This post will serve as a summary of my posts related to my not very scientific analysis of data access layers. These posts won't be tutorials but more pointers to things I liked/didn't like about each method as well as the main bits of interesting code.

For more detail grab the code from: http://code.google.com/p/browniesbikes/. Along with the code is also my NUnit tests.

DataReaders and Stored Procs:

Listing Data
Retrieving a single item - implemented post coming soon
Inserting Data - implemented post coming soon
Updating Data - implemented post coming soon

TableAdapters:

Listing Data
Retrieving a single item - implemented post coming soon
Inserting Data - implemented post coming soon
Updating Data - implemented post coming soon

NHibernate:

Implemented - posts coming soon

LinqToSQL

Implemented - posts coming soon

SubSonic

partially implemented

Data Access Application Block (Enterprise Library)

meaning to implement it someday.

TableAdapters - The List

Andrew Browne — Sat, 05 Jan 2008 09:19:25 GMT

Most of my post on retrieving my Product list focused on the Stored Procedure. When it came time to implement the same list with a TableAdapter all that work was already done for me. My steps became:

New dataset.
Drag my stored procedure from server explorer.
Rename the table and tableadapter
And there we have it:

I then double clicked on the designer and edited the codebehind file to allow my DataRows to implement my IProduct interface:

    1 using System;
    2 using BrowniesBikes.DTO;
    3 
    4 namespace BrowniesBikes.Data.TableAdapter {
    5 
    6 
    7     partial class ProductDS
    8     {
    9         partial class ProductListRow : IProduct
   10         {
   11             #region IProduct Members
   12 
   13             public int? PhotoID
   14             {
   15                 get { throw new System.NotImplementedException(); }
   16                 set { throw new System.NotImplementedException(); }
   17             }
   18 
   19             ...etc...
   20             #endregion
   21         }
   22     }
   23 }

My DAL class ended up with very little code:

   18         public IEnumerable<IProduct> GetProductList(
   19             string searchString, 
   20             string sortExpression, 
   21             int startRow, 
   22             int maxRows)
   23         {
   24             int endRow = startRow + maxRows;
   25             ProductListTableAdapter productListTableAdapter = 
   26                 new ProductListTableAdapter();
   27 
   28             int? totalProducts = 0;
   29 
   30             ProductDS.ProductListDataTable listDataTable = 
   31                 productListTableAdapter.GetData(
   32                 searchString, 
   33                 startRow, 
   34                 endRow, 
   35                 sortExpression, 
   36                 ref totalProducts); 
   37 
   38             foreach (ProductDS.ProductListRow row in 
   39                 listDataTable.Rows)
   40             {
   41                 yield return row;
   42             }
   43         }

Deceptively easy. Keep an eye out for my post on inserting and updating as well as TableAdapter maintenance. There are some major pain points coming your way.

DataReaders and Stored Procs - The List

Andrew Browne — Sun, 25 Nov 2007 23:25:54 GMT

Me: I'm going to write some example code to properly compare table adapters with my other options.

Marc: But you already hate table adapters how are you going to be objective?

...a day later...

Me: Okay I'll start with stored procedures and data readers, nothing can be less fun than that.

So I proceeded to have lots of fun implementing my web site data layer using data readers and stored procedures.

To begin with I wanted to fill my GridView with some data. This is something I'm sure we've all done so many times. When I was first working with ASP.NET I begin with Scott Mitchell's data tutorials. These tutorial use dynamic SQL. After lots of advice and help from the guys on the SQLDownUnder list I have eliminated any dynamic SQL from my stored procedure. I think the result is nice and reasonably maintainable. This stored procedure has the following features that I find are usually requested in the systems I build:

Paging
Sorting
Searching

To do paging two queries are required one that returns the page of results and one that gets the total number of results. I have chosen to make the total rows an output parameter for my stored procedure. This has two advantages I can see. The first advantage is that the where clause is repeated across both queries and this way they are in the same place for maintenance. The second plus is that it allows a single database round trip to get the list.

1 -- Author: Andrew Browne

2 -- Create date: 12 November 2007

3 -- Description: Retrieves a product list one

4 -- page at a time

5 -- =============================================

6 CREATE PROCEDURE [BrowniesBikes].[GetProductList]

7 @SearchString NVARCHAR(50) = '',

8 @StartRow INT = 1,

9 @EndRow INT = 10,

10 @SortColumn NVARCHAR(50) = '',

11 @TotalProducts INT OUTPUT

12 AS

13 BEGIN

14 SET NOCOUNT ON;

16 DECLARE @LIKE_SEARCH as nvarchar(50)

17 SET @LIKE_SEARCH = '%' + lower(@SearchString) + '%'

19 SELECT @TotalProducts = COUNT(*)

20 FROM Production.Product

21 WHERE(lower(Name) LIKE @LIKE_SEARCH

22 OR lower(ProductNumber) LIKE @LIKE_SEARCH)

24 SELECT RowRank, ProductID, Name, ProductNumber

25 FROM

26 (SELECT ProductID,

27 Name,

28 ProductNumber,

29 ROW_NUMBER()

30 OVER(

31 ORDER BY

32 CASE WHEN

33 @SortColumn = 'ProductNumber'

34 THEN

35 ProductNumber

36 ELSE

37 Name

38 END

39 )

40 AS RowRank FROM Production.Product

41 WHERE(lower(Name) LIKE @LIKE_SEARCH OR

42 lower(ProductNumber) LIKE @LIKE_SEARCH)

43 ) AS ProductsWithRowNumber

44 WHERE RowRank > @StartRow

45 AND RowRank <= @EndRow

46 END

This stored procedure will only work with SQL 2005 because of the over clause.

The code to retrieve this was fairly straight forward if you want all the details grab the source code. The main pain point that I found was this routine for manually mapping the results from the reader:

   78         private static Product 
   79             GetProductSummaryFromReader(
   80                 IDataReader reader
   81             )
   82         {
   83             Product product = new Product();
   84             product.ProductID = 
   85                 Convert.ToInt32(reader["ProductId"]);
   86             product.Name = 
   87                 Convert.ToString(reader["Name"]);
   88             product.ProductNumber = 
   89                 Convert.ToString(
   90                     reader["ProductNumber"]
   91                     );
   92             return product;
   93         }

This code feels a little fragile with all the convert calls in there but at least it's all in one place.

First Post!

Andrew Browne — Sun, 18 Nov 2007 05:59:52 GMT

This blog is primarily the result of the idea that "there should be a better way". I think most of us are constantly looking for faster/easier/more maintainable ways of doing things.

In my case I am currently working in ASP.NET on public facing websites. After many conversations with colleagues about datasets/tableadapters vs everything else I decided that all the talk in the world wasn't going to get a well considered result. Over the last few months I have been exploring different .NET data access strategies.

My method of comparison so far has been to use each of the technologies in the data layer for my very simple List/View/Add/Edit sample app. The example application is based on the AdventureWorks Cycles and I've named it Brownie's Bikes. The example is probably a bit simple at the moment but we'll fix that over time.

My work is up at http://code.google.com/p/browniesbikes/

My plan is for my first few posts to compare the different strategies and technologies I have used to implement the data access in Brownie's Bikes. While doing this work I have also become very excited by better ways of developing the UI and architecture for websites so expect some posts about these topics too.

Disclaimer: I only know as much as I know right now. I am very interested in better ways of doing things. If you don't like my ideas I'd love to try yours. If you have a better idea or I am wrong let me know in an email/comment/link to your blog. I have just finished the fourth data layer for my sample app and am planning more. I'm very open to trying any idea that looks reasonable.