using System; using System.Collections.Generic; var list = new List<int> { 1, 2 }; foreach(var item in list) Console.Write(item);
using System; using System.Collections.Generic; var list = new List<int> { 1, 2 }; foreach(var item in list) Console.Write(item);
Expression ParseMemberAccess(Type type, Expression instance) Expression of type 'System.Guid' cannot be used for parameter of type 'System.Object' of method 'Boolean Equals(System.Object)'
If multiple operations complete at once for the same application,
AspNetSynchronizationContext will ensure that they execute one at a
time. They may execute on any thread, but that thread will have the
identity and culture of the original page
Here’s a summary of what’s new in this preview release:
NavigationManager
System.Security.Cryptography
support on WebAssemblyDefaultScheme
IFormFile
/IFormFileCollection
support for authenticated requests in minimal APIsHttpResults
interfaces Here’s a summary of what’s new in this preview release:
QuickGrid
component for BlazorMapGroup
support for more extension methods SELECT Title FROM Book WHERE Desc LIKE '%cat%';
var cats = context.Chapters.Where(item => item.Text.Contains("cat")).ToList();
SELECT "c"."Text" FROM "Chapters" AS "c" WHERE ('cat' = '') OR (instr("c"."Text", 'cat') > 0)
var cats = context.Chapters.Where(item => item.Text.StartsWith("cat")).ToList(); // SELECT "c"."Text", FROM "Chapters" AS "c" WHERE "c"."Text" IS NOT NULL AND ("c"."Text" LIKE 'cat%')
var cats = context.Chapters.Where(item => item.Text.EndsWith("cat")).ToList(); // SELECT "c"."Title" FROM "Chapters" AS "c" WHERE "c"."Text" IS NOT NULL AND ("c"."Text" LIKE '%cat')
using System.Collections.Generic; namespace EFCoreSQLiteFTS.Entities { public class User { public int Id { get; set; } public string Name { get; set; } public ICollection<Chapter> Chapters { get; set; } } public class Chapter { public int Id { get; set; } public string Title { get; set; } public string Text { get; set; } public User User { get; set; } public int UserId { get; set; } } }
CREATE VIRTUAL TABLE "Chapters_FTS" USING fts5("Text", "Title", content="Chapters", content_rowid="Id")
private static void createFtsTables(ApplicationDbContext context) { // For SQLite FTS // Note: This can be added to the `protected override void Up(MigrationBuilder migrationBuilder)` method too. context.Database.ExecuteSqlRaw(@"CREATE VIRTUAL TABLE IF NOT EXISTS ""Chapters_FTS"" USING fts5(""Text"", ""Title"", content=""Chapters"", content_rowid=""Id"");"); }
-- Create a table. And an external content fts5 table to index it. CREATE TABLE tbl(a INTEGER PRIMARY KEY, b, c); CREATE VIRTUAL TABLE fts_idx USING fts5(b, c, content='tbl', content_rowid='a'); -- Triggers to keep the FTS index up to date. CREATE TRIGGER tbl_ai AFTER INSERT ON tbl BEGIN INSERT INTO fts_idx(rowid, b, c) VALUES (new.a, new.b, new.c); END; CREATE TRIGGER tbl_ad AFTER DELETE ON tbl BEGIN INSERT INTO fts_idx(fts_idx, rowid, b, c) VALUES('delete', old.a, old.b, old.c); END; CREATE TRIGGER tbl_au AFTER UPDATE ON tbl BEGIN INSERT INTO fts_idx(fts_idx, rowid, b, c) VALUES('delete', old.a, old.b, old.c); INSERT INTO fts_idx(rowid, b, c) VALUES (new.a, new.b, new.c); END;
using System; using System.Collections.Generic; using System.Linq; using Microsoft.EntityFrameworkCore; using Microsoft.EntityFrameworkCore.ChangeTracking; namespace EFCoreSQLiteFTS.DataLayer { public static class EFChangeTrackerExtensions { public static List<(EntityState State, TEntity NewEntity, TEntity OldEntity)> GetChangedEntities<TEntity>(this DbContext dbContext) where TEntity : class, new() { if (!dbContext.ChangeTracker.AutoDetectChangesEnabled) { // ChangeTracker.Entries() only calls `Try`DetectChanges() behind the scene. dbContext.ChangeTracker.DetectChanges(); } return dbContext.ChangeTracker.Entries<TEntity>() .Where(IsEntityChanged) .Select(entityEntry => (entityEntry.State, entityEntry.Entity, createWithValues<TEntity>(entityEntry.OriginalValues))) .ToList(); } private static bool IsEntityChanged(EntityEntry entry) { return entry.State == EntityState.Added || entry.State == EntityState.Modified || entry.State == EntityState.Deleted || entry.References.Any(r => r.TargetEntry?.Metadata.IsOwned() == true && IsEntityChanged(r.TargetEntry)); } private static T createWithValues<T>(PropertyValues values) where T : new() { var entity = new T(); foreach (var prop in values.Properties) { var value = values[prop.Name]; if (value is PropertyValues) { throw new NotSupportedException("nested complex object"); } else { prop.PropertyInfo.SetValue(entity, value); } } return entity; } } }
using System.Collections.Generic; using System.Data; using System.Text.RegularExpressions; using EFCoreSQLiteFTS.Entities; using Microsoft.EntityFrameworkCore; namespace EFCoreSQLiteFTS.DataLayer { public static class FtsNormalizer { private static readonly Regex _htmlRegex = new Regex("<[^>]*>", RegexOptions.Compiled); public static string NormalizeText(this string text) { if (string.IsNullOrWhiteSpace(text)) { return string.Empty; } // Remove html tags text = _htmlRegex.Replace(text, string.Empty); // TODO: add other normalizers here, such as `remove diacritics`, `fix Persian Ye-Ke` and so on ... return text; } } public static class UpdateFtsTriggers { public static void UpdateChapterFTS( this DbContext context, List<(EntityState State, Chapter NewEntity, Chapter OldEntity)> changedChapters) { var database = context.Database; try { database.BeginTransaction(IsolationLevel.ReadCommitted); foreach (var (State, NewEntity, OldEntity) in changedChapters) { var chapterNew = NewEntity; var chapterOld = OldEntity; var normalizedNewText = chapterNew.Text.NormalizeText(); var normalizedOldText = chapterOld.Text.NormalizeText(); var normalizedNewTitle = chapterNew.Title.NormalizeText(); var normalizedOldTitle = chapterOld.Title.NormalizeText(); switch (State) { case EntityState.Added: if (shouldSkipAddedChapter(chapterNew)) { continue; } database.ExecuteSqlRaw("INSERT INTO Chapters_FTS(rowid, Text, Title) values({0}, {1}, {2});", chapterNew.Id, normalizedNewText, normalizedNewTitle); break; case EntityState.Modified: if (shouldSkipModifiedChapter(chapterNew, chapterOld)) { continue; } // This format is important! Otherwise we will get `SQLite Error 11: 'database disk image is malformed'.` error! database.ExecuteSqlRaw(@"INSERT INTO Chapters_FTS(Chapters_FTS, rowid, Text, Title) VALUES('delete', {0}, {1}, {2}); ", chapterOld.Id, normalizedOldText, normalizedOldTitle); database.ExecuteSqlRaw("INSERT INTO Chapters_FTS(rowid, Text, Title) values({0}, {1}, {2});", chapterNew.Id, normalizedNewText, normalizedNewTitle); break; case EntityState.Deleted: // This format is important! Otherwise we will get `SQLite Error 11: 'database disk image is malformed'.` error! database.ExecuteSqlRaw(@"INSERT INTO Chapters_FTS(Chapters_FTS, rowid, Text, Title) VALUES('delete', {0}, {1}, {2}); ", chapterOld.Id, normalizedOldText, normalizedOldTitle); break; } } } finally { database.CommitTransaction(); } } private static bool shouldSkipAddedChapter(Chapter chapterNew) { // TODO: add your logic to avoid indexing this item return false; } private static bool shouldSkipModifiedChapter(Chapter chapterNew, Chapter chapterOld) { // TODO: add your logic to avoid indexing this item return chapterNew.Text == chapterOld.Text && chapterNew.Title == chapterOld.Title; } } }
namespace EFCoreSQLiteFTS.DataLayer { public class ApplicationDbContext : DbContext { public ApplicationDbContext(DbContextOptions options) : base(options) { } public DbSet<Chapter> Chapters { get; set; } public DbSet<User> Users { get; set; } public override int SaveChanges() { var changedChapters = this.GetChangedEntities<Chapter>(); this.ChangeTracker.AutoDetectChangesEnabled = false; // for performance reasons, to avoid calling DetectChanges() again. var result = base.SaveChanges(); this.ChangeTracker.AutoDetectChangesEnabled = true; this.UpdateChapterFTS(changedChapters); return result; } } }