Data Access Layer (DAL) is an important part in almost all architectures. I encountered problems creating DAL for large databases — maintaining DAL for these databases was another nightmare. So I thought of a generic solution to this problem, which was to auto generate the DAL.
I made use of
System.CodeDom which is a code generator to produce source code in a particular programming language.
Using the Code
In order to generate DAL in your ASP.NET project follow the below steps:
- Add a reference of DalProvider.dll which is a DAL Auto-Generator Library
- Add the following under compilation tag in the web.config
This allows the compilation of any file with the ".dal" extension added to the project with our DAL auto generation library.
- Add a XML file to the App_Code folder in the below mentioned format with the extension ".dal"
<connectionString>Data Source =XXXXX; Initial Catalog = XXXXX;
User Id =XXXXX; Password=XXXXX
In this XML file under the "dal" root tag we need to mention the connection string of the database as well as the namespace to access the auto generated DAL.
- Compile your ASP.NET project. This generates the DAL with the following features:
- Namespace "DAL1" as specified in the XML file
- All tables are represented as classes with its columns as member fields that can be accessed using property with name in the following pattern "Col" + Column Name. This enables the users to create objects of tables.
DAL1.TableName table1 = new DAL1.TableName();
tabel1.ColColumnName1 = "2";
table2.ColColumnName2 = "Trial";
Response.Write ("Data in column2:" + table2.ColColumnName2);
- All stored procedure access methods are defined under the
DataProcedure class. Thus to access a stored procedure the user has to use the respective stored procedure access function ("Access"+StoredProcedureName).
DAL2.DataProcedure dbObject = new DAL2.DataProcedure();
DataTable dataResult=new DataTable();
int returnStatus = dbObject.AccessStoredProcedureName(ref dataResult,
"21", "Thomas", "Atlas", "ITDept");
A reference to a datatable has to be passed to this function to retrieve the records fetched using the stored procedure.
The code is big but simple. The work flow of this library is as below:
param.name AS [Name],
ISNULL(baset.name, N'') AS [SystemType],
CAST(CASE WHEN baset.name IN (N'char', N'varchar', N'binary', N'varbinary',
THEN param.prec ELSE param.length END AS int) AS [Length],
CAST(param.xprec AS int) AS [NumericPrecision],
CAST(param.xscale AS int) AS [NumericScale],
null AS [DefaultValue],
CASE param.isoutparam WHEN 1 THEN param.isoutparam WHEN 0 THEN
CASE param.name WHEN ''
THEN 1 ELSE 0 END END AS bit) AS [IsOutputParameter]
dbo.sysobjects AS sp
INNER JOIN sysusers AS ssp ON ssp.uid = sp.uid
INNER JOIN syscolumns AS param ON (param.number = 1) AND (param.id=sp.id)
LEFT OUTER JOIN systypes AS baset ON baset.xusertype =
param.xtype and baset.xusertype = baset.xtype
(sp.xtype = N'P' OR sp.xtype = N'RF')and(sp.id= ? and ssp.name=N'dbo')
CAST(param.colid AS int) ASC
Combine all the information and generate functions to access stored procedures
Points of Interest
This solution is a good example of using