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To use
LinqDataSource control to query a database, entity objects must be created to
represent the database and its tables. You can use the Object Relational
Designer or the SqlMetal.exe utility to generate these objects.The ContextTypeName property must be set to the object
that represents the database and the TableName property to the object that
represents the database table.
Object Relational Designer
The Object Relational Designer (O/R Designer) provides a
visual design surface for creating LINQ to SQL entity classes and associations
(relationships) based on objects in a database. In other words, the O/R Designer
is used to create an object model in an application that maps to objects in a
database. The O/R Designer also provides functionality to map stored procedures
and functions to DataContext methods for returning data and hydrating entity
classes. The O/R Designer also provides the ability to design inheritance
relationships between entity classes. The O/R Designer currently supports only
SQL Server 2000 and later, and SQL Server Express databases
The O/R Designer has two distinct areas on its design
surface: the entities pane on the left, and the methods pane on the right. The
entities pane is the main design surface that displays the entity classes
defined in the file. The methods pane is the design surface that displays the
DataContext methods that are mapped to stored procedures and functions. You can
hide the methods pane. Using methods pane is out of scope of this article.
Code Generation tool (SqlMetal.Exe)
The SqlMetal command-line tool is used to generate code
and mapping for the LINQ to SQL component of the .NET Framework. By applying
options as listed below, you can instruct SqlMetal to perform a number of
different actions, including the following:
From a database, generate source code and mapping
attributes or a mapping file.
From a database, generate an intermediate DBML
file for customization.
From a DBML file, generate code and mapping
attributes or a mapping file.
The file is located by default at
[drive:]\program files\microsoft sdks\windows\v6.0A\bin.
>sqlmetal [options] [<input file>]
Example 1: To generate a .dbml file with extracted SQL metadata,
issue the following command in the Visual Studio Command Prompt
window.
>sqlmetal /server:myserver /database:northwind
/dbml:mymeta.dbml
Example 2: To generate a .dbml file with extracted SQL metadata from
an .mdf file with SQL Server Express, issue the following
command
>sqlmetal /dbml:mymeta.dbml mydbfile.mdf
Walkthrough 2:
Connecting Sql Server Express Database using O/R
Designer and LinqDataSource and perform queries on a table to display data in a
ASP.Net webpage
Add a new Webpage(Default2.aspx) to the existing WebSite
project you have just created to test the sample Walthrough 1.
In the WebSite Menu, select “Add New Item” command to
choose the “Linq to Sql Classes” from the available list of templates in the
dialog. It creates a new entity class’s file called DataClasses.dbml in the
website’s App_Code folder.
After you add the new LINQ to SQL file to the project,
the empty design surface represents a DataContext ready to be configured. The
DataContext name corresponds to the name that you provided for the .dbml file.
For this walkthrough, because you named the LINQ to SQL file DataClasses.dbml,
the DataContext is named DataClassesDataContext. You can verify this by clicking
an empty area on the designer and inspecting the Properties window.
Next step is to create LINQ to SQL classes that are
mapped to database tables by dragging tables from Server Explorer/Database
Explorer onto the O/R Designer. The result is a LINQ to SQL entity class that
maps to the table in the database. (Pic5)
In Server Explorer/Database Explorer, locate the tables
in the SQL Server version of the sales.dbf sample database used in this article.
Drag the Product node from Server Explorer/Database
Explorer onto the O/R Designer surface.
An entity class named Product is created to represent a
single product from the Product table. It has properties that correspond to the
columns in the Product table.
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