Learning by Walkthroughs (LINQ to SQL)
The LINQ to SQL documentation provides several walkthroughs. This topic addresses some general walkthrough issues (including troubleshooting), and provides links to several entry-level walkthroughs for learning about LINQ to SQL.
Note
The walkthroughs in this Getting Started section expose you to the basic code that supports LINQ to SQL technology. In actual practice, you will typically use the Object Relational Designer and Windows Forms projects to implement your LINQ to SQL applications. The O/R Designer documentation provides examples and walkthroughs for this purpose. For more information, see Object Relational Designer (O/R Designer) and Object Relational Designer (O/R Designer).
Getting Started Walkthroughs
Several walkthroughs are available in this section. These walkthroughs are based on the sample Northwind database, and present LINQ to SQL features at a gentle pace with minimal complexities.
A typical progression to follow would be as follows:
Objective |
Visual Basic |
C# |
|---|---|---|
Create an entity class and execute a simple query. |
Walkthrough: Simple Object Model and Query (Visual Basic) (LINQ to SQL) |
Walkthrough: Simple Object Model and Query (C#) (LINQ to SQL) |
Add a second class and execute a more complex query. (Requires completion of previous walkthrough). |
Walkthrough: Querying Across Relationships (Visual Basic) (LINQ to SQL) |
Walkthrough: Querying Across Relationships (C#) (LINQ to SQL) |
Add, change, and delete items in the database. |
||
Use stored procedures. |
Walkthrough: Using Only Stored Procedures (Visual Basic) (LINQ to SQL) |
Walkthrough: Using Only Stored Procedures (C#) (LINQ to SQL) |
General
The following information pertains to these walkthroughs in general:
Environment: Each LINQ to SQL walkthrough uses Visual Studio as its integrated development environment (IDE).
SQL engines: These walkthroughs are written to be implemented by using SQL Server Express. If you do not have SQL Server Express, you can download it free of charge. For more information, see Downloading Sample Databases (LINQ to SQL).
Note
LINQ to SQL walkthroughs use a file name as a connection string. Simply specifying a file name is a convenience that LINQ to SQL provides for SQL Server Express users. Always pay attention to security issues. For more information, see Security in LINQ to SQL.
LINQ to SQL walkthroughs typically require the Northwind sample database. For more information, see Downloading Sample Databases (LINQ to SQL).
The dialog boxes and menu commands you see in walkthroughs might differ from those described in Help, depending on your active settings or Visual Studio edition. To change your settings, click Import and Export Settings on the Tools menu. For more information, see Working with Settings.
For walkthroughs that address multi-tier scenarios, a server must be located on a computer that is distinct from the development computer, and you must have appropriate permissions to access the server.
The name of the class that typically represents the Orders table in the Northwind sample database is [Order]. The escaping is required because Order is a keyword in Visual Basic.
Troubleshooting
Run-time errors can occur because you do not have sufficient permissions to access the databases used in these walkthroughs. See the following steps to help resolve the most common of these issues.
Log-On Issues
Your application might be trying to access the database by way of a database logon it does not accept.
To verify or change the database log on
On the Windows Start menu, point to All Programs, Microsoft SQL Server 2005, point to Configuration Tools, and then click SQL Server Configuration Manager.
In the left pane of the SQL Server Configuration Manager, click SQL Server 2005 Services.
In the right pane, right-click SQL Server (SQLEXPRESS), and then click Properties.
Click the Log On tab and verify how you are trying to log on to the server.
In most cases, Local System works.
If you make a change, click Restart to restart the service.
Protocols
At times, protocols might not be set correctly for your application to access the database. For example, the Named Pipes protocol, which is required for walkthroughs in LINQ to SQL, is not enabled by default.
To enable the Named Pipes protocol
In the left pane of the SQL Server Configuration Manager, expand SQL Server 2005 Network Configuration, and then click Protocols for SQLEXPRESS.
In the right pane, make sure that the Named Pipes protocol is enabled. If it is not, right-click Name Pipes and then click Enable.
You will have to stop and restart the service. Follow the steps in the next block.
Stopping and Restarting the Service
You must stop and restart services before your changes can take effect.
To stop and restart the service
In the left pane of the SQL Server Configuration Manager, click SQL Server 2005 Services.
In the right pane, right-click SQL Server (SQLEXPRESS), and then click Stop.
Right-click SQL Server (SQLEXPRESS), and then click Restart.