If reports are to be used in distributed applications such as web applications, all required files need to be shared between the systems involved or between the client and the server and kept synchronized at all times. Hence, it is a good idea to save the project files in a central database. However, this solution can become rather complex, especially when a project references pictures, drilldown projects, and other external files via local data paths, which then also need to be valid on another system.

With repository mode, the use of local files in a project can be done away with entirely, and List & Label projects as well as all the files they require can be managed at a central location (the so-called repository) with little effort - such as in a database or by a web service.

Basic Principles

In repository mode, List & Label does not save and load the files used in a report on its own. Instead of file paths and names, unique repository IDs are used. You will need to implement the IRepository Interface yourself and pass it to the ListLabel object. From this point onwards, List & Label will query your user-defined repository for the file content belonging to a repository ID, or transmit the ID along with the corresponding file content to the repository to be saved. Whether the files in the repository are managed by an SQL database, a web service, or some other storage solution depends entirely on your IRepository implementation. In this case, loading and saving of entries in the repository takes place exclusively via streams.
The following schematic diagram shows how a report with the ID "123" is loaded via an IRepository implementation managing an internal SQL database:

Implementation

All functions to which the file path of the project (e.g. "C:\Reports\Invoice.lst") was previously passed are now assigned the repository ID (e.g. "repository://{53F875F0-6177-8AD5-01B44E3A9867}" instead.

In repository mode, "files" become "repository items", and filenames become "repository IDs". In addition to its ID, each repository item possesses a type, a time stamp, and a descriptor (string with variable length which contains internal information). Hence, in addition to the file content, your repository implementation will also need to be able to save and retrieve at least these four pieces of information for each repository item.

Tips

• Use the class RepositoryImportUtil to import existing local files and/or create new projects in the repository.

• You can use the RepositoryItemDescriptor class to change the display name shown in the selection dialogs in the Designer instead of the internal repository ID.

• Accessing the repository takes place sequentially. However, if you use the same repository object for multiple List & Label instances, or if the data storage used is not thread-safe, then synchronization is required.

• Web applications: In order to be able to add large files into the repository, the two parameters maxRequestLength and executionTimeout should be set in the web.config to sufficiently large values. This is also shown in the included ASP.NET samples.