Скачать или смотреть Solving the SQLite Data Retrieval Issue in Xamarin.Android: Why You Get Default Objects

Discover how to fix the problem of retrieving default objects from SQLite in Xamarin.Android by adjusting visibility of class members.
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This video is based on the question https://stackoverflow.com/q/66025978/ asked by the user 'Asaf' ( https://stackoverflow.com/u/15052161/ ) and on the answer https://stackoverflow.com/a/66050945/ provided by the user 'Asaf' ( https://stackoverflow.com/u/15052161/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem

If you are working with Xamarin.Android and SQLite, you may encounter a frustrating issue: retrieving data from your SQLite database returns objects with default values, rather than the expected data. Instead of seeing the information you stored, you find that all your objects look the same, as if initialized through a default constructor. Let's dive into why this happens and how to resolve it effectively.

The Issue Explained

The problem stems from the visibility of class members in your data model. In object-oriented programming, when you define a class, its members (properties, fields, etc.) can be private or public. This visibility plays a crucial role when SQLite tries to map database records to your objects.

Only Public Members Are Mapped: SQLite will only map the properties of your class that are marked as public. If the properties are not set to this visibility level, they will not be populated when retrieving data from the database.

The Attempted Solutions

You might have tried the following codes to retrieve data from your SQLite database, but encountered the same issue of receiving default objects:

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Despite these efforts yielding the expected number of objects, they all displayed default values because the properties were not accessible.

The Solution

After facing this problem, the solution is straightforward yet significant: Make all members of your class public. Here’s how you can fix the issue:

Steps to Fix the Problem:

Review Your Class Structure: Ensure that your data model class has all relevant properties marked as public. For example:

[[See Video to Reveal this Text or Code Snippet]]

Recompile Your Project: After making changes to your class, make sure to recompile your solution to apply the adjustments.

Test the Data Retrieval Again: Use your existing methods to retrieve data from SQLite. You should now see your objects populated with the correct values rather than defaults.

Debug for Any Additional Issues: If problems persist, verify your database schema to ensure it matches your data model.

Conclusion

By ensuring that all the properties in your data model class are public, you allow the SQLite library to appropriately map database entries to your objects. This simple yet critical step can save you significant time and frustration in your development process. Next time you encounter default objects when retrieving from SQLite, remember: accessibility matters!

With these adjustments, you'll be able to seamlessly retrieve data from your SQLite database, making your Xamarin.Android application robust and functional.