Getting Started with LinqConnect for Metro AppsLinqConnect is a lightweight, high-performance ORM (Object-Relational Mapping) solution that makes working with databases from .NET applications straightforward. When building Metro-style (now commonly referred to as Windows Store or UWP-style) apps, using an ORM such as LinqConnect can speed development by letting you work with strongly typed classes instead of raw SQL. This article walks through the concepts, setup, and a practical example to help you get started with LinqConnect for Metro apps.
What is LinqConnect?
LinqConnect is an ORM from Devart that supports LINQ queries, change tracking, and object mapping to database structures. It provides familiar LINQ-to-SQL style APIs while supporting multiple databases and offering performance optimizations. For Metro (Windows Store/UWP) apps, LinqConnect provides a way to access local and remote databases safely and efficiently within the app’s sandbox and security model.
Prerequisites
- Visual Studio (2013 or later) with Windows Store / UWP development workload installed.
- A basic understanding of C#, .NET, and LINQ.
- LinqConnect package compatible with Metro/UWP. Check Devart’s site or NuGet for the correct package/version.
- A target database: common choices are SQLite (for local storage) or a remote SQL Server accessed via web services or direct connection if allowed.
Installation
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Open your Metro/UWP project in Visual Studio.
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Install LinqConnect via NuGet (if available for your target) or add the LinqConnect assemblies to your project. Example using NuGet Package Manager Console:
Install-Package LinqConnectForMetro -Version x.y.z(Replace with the actual package name and version available for Metro/UWP from Devart or NuGet.)
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Add any required runtime dependencies (for example, native SQLite libraries if using SQLite).
Project Configuration
- App capabilities: If your app needs network access to connect to remote databases, enable the appropriate capabilities (InternetClient/InternetClientServer) in the app manifest.
- Threading: Database operations can be I/O-bound and should be done off the UI thread. Use async/await and Task.Run where appropriate.
- Storage locations: For local databases, store the database file in ApplicationData.Current.LocalFolder to ensure write access.
Defining the Data Model
LinqConnect uses classes with attributes (or fluent mapping) to map C# classes to database tables. Example model for a simple notes app:
using System; using System.Data.Linq.Mapping; [Table(Name = "Notes")] public class Note { [Column(IsPrimaryKey = true, IsDbGenerated = true)] public int Id { get; set; } [Column] public string Title { get; set; } [Column] public string Content { get; set; } [Column] public DateTime CreatedAt { get; set; } } Create a data context to manage queries and changes:
using System.Data.Linq; public class NotesDataContext : DataContext { public Table<Note> Notes; public NotesDataContext(string connectionString) : base(connectionString) { } } Creating and Initializing the Database
For a local SQLite-backed DB stored in the app’s local folder, build a connection string pointing to the database file location. On first run, create the database schema.
using System.IO; using Windows.Storage; public static async Task<string> GetConnectionStringAsync() { var localFolder = ApplicationData.Current.LocalFolder; var dbFile = await localFolder.CreateFileAsync("notes.db", CreationCollisionOption.OpenIfExists); return $"Data Source={dbFile.Path};Cache=Shared;"; } Then initialize and create tables:
var connString = await GetConnectionStringAsync(); using (var db = new NotesDataContext(connString)) { if (!db.DatabaseExists()) { db.CreateDatabase(); } } Note: APIs and exact methods may differ by LinqConnect version; refer to the library’s docs for precise method names for database existence checks and creation.
Basic CRUD Operations
Insert a note:
public async Task AddNoteAsync(Note note) { var connString = await GetConnectionStringAsync(); using (var db = new NotesDataContext(connString)) { db.Notes.InsertOnSubmit(note); await Task.Run(() => db.SubmitChanges()); } } Query notes:
public async Task<List<Note>> GetNotesAsync() { var connString = await GetConnectionStringAsync(); using (var db = new NotesDataContext(connString)) { return await Task.Run(() => db.Notes.OrderByDescending(n => n.CreatedAt).ToList()); } } Update a note:
public async Task UpdateNoteAsync(Note updated) { var connString = await GetConnectionStringAsync(); using (var db = new NotesDataContext(connString)) { var existing = db.Notes.Single(n => n.Id == updated.Id); existing.Title = updated.Title; existing.Content = updated.Content; await Task.Run(() => db.SubmitChanges()); } } Delete a note:
public async Task DeleteNoteAsync(int id) { var connString = await GetConnectionStringAsync(); using (var db = new NotesDataContext(connString)) { var note = db.Notes.Single(n => n.Id == id); db.Notes.DeleteOnSubmit(note); await Task.Run(() => db.SubmitChanges()); } } Asynchronous Patterns and UI Thread Safety
- Wrap blocking LinqConnect operations in Task.Run to avoid blocking the UI thread (as LinqConnect’s SubmitChanges and queries may be synchronous).
- Use async/await to keep code readable and responsive.
- If using change notifications to update the UI, marshal back to the UI thread via CoreDispatcher.RunAsync or equivalent.
Transactions and Concurrency
LinqConnect supports transactions via the underlying connection. For multi-step operations, use a transaction scope or the data context’s transaction support to ensure atomicity. Be mindful of concurrent access patterns in UWP apps — serialize writes where necessary.
Error Handling and Logging
- Catch database exceptions (connection issues, constraint violations) and present user-friendly messages.
- Use logging during development to capture SQL generated by LinqConnect for debugging performance or mapping issues.
Performance Tips
- Prefer compiled queries for frequently used LINQ expressions.
- Limit returned columns with projections (select only needed fields) rather than selecting entire entities when possible.
- Use paging for large result sets.
- Reuse DataContext for related operations instead of creating many short-lived contexts, but avoid long-lived contexts that keep large change-tracking state.
Testing and Debugging
- Unit test database logic with an in-memory or local test database.
- Seed test data to validate queries and migrations.
- Enable SQL logging in LinqConnect (if supported) to inspect generated queries.
Deployment Considerations
- If the app connects to remote databases, consider using a web API as an intermediary to avoid exposing database credentials and to better control access.
- For local databases, ensure migrations or schema updates run safely on app updates — implement version checks and migration scripts as needed.
Troubleshooting Common Issues
- “Database file locked” — ensure all connections are closed before schema updates; use shared cache if supported.
- Mapping mismatches — confirm attribute names/types match the DB schema and check for nullable mismatches.
- Permission errors — verify the database file is stored in ApplicationData.Current.LocalFolder and required capabilities are set.
Example Small App Structure
- Models/Note.cs — entity definitions.
- Data/NotesDataContext.cs — data context and DB init.
- Services/NoteRepository.cs — async CRUD wrappers.
- ViewModels — bind to UI and call repository via async methods.
- Views — XAML pages using ObservableCollection for lists and data binding.
Resources
- Official LinqConnect documentation for Metro/UWP (check Devart).
- SQLite for UWP docs if using SQLite.
- UWP app lifecycle and storage documentation from Microsoft.
This guide provides a practical path to get LinqConnect running in a Metro-style app, covering setup, model mapping, CRUD operations, and deployment considerations. Adjust API calls to match the LinqConnect version you use and follow Devart’s documentation for specifics.
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