entity-framework-core

问题 Function need to return Task<List<Record>> Following both options are returning Task<List<Record>> , which one is more efficient? Is there any standard way here? Option 1 : Task<List<Record>> GetRecords() { return DbContext.Set<Record>.Where(predicate).ToListAsync(); } Option 2: Task<List<Record>> GetRecords() { return DbContext.Set<Record>.Where(predicate).AsAsyncEnumerable().ToList(); } 回答1: Go for option 1 ToListAsync as the source code of AsAsyncEnumerable explicitly mentions This is an

问题 I built a console project and use code first to map model to database. When I run the command of Add-Migration InitialMigration , I get an error: Method 'Create' in type 'Microsoft.EntityFrameworkCore.SqlServer.Query.Internal.SqlServerSqlTranslatingExpressionVisitorFactory' from assembly 'Microsoft.EntityFrameworkCore.SqlServer, Version=3.1.5.0, Culture=neutral, PublicKeyToken=adb9793829ddae60' does not have an implementation. The DbContext is: class ActorDbContext : DbContext { public DbSet

问题 I built a console project and use code first to map model to database. When I run the command of Add-Migration InitialMigration , I get an error: Method 'Create' in type 'Microsoft.EntityFrameworkCore.SqlServer.Query.Internal.SqlServerSqlTranslatingExpressionVisitorFactory' from assembly 'Microsoft.EntityFrameworkCore.SqlServer, Version=3.1.5.0, Culture=neutral, PublicKeyToken=adb9793829ddae60' does not have an implementation. The DbContext is: class ActorDbContext : DbContext { public DbSet

问题 I am using a LINQ query on a DbSet<T> : await _dbContext.Users.AnyAsync(u => u.Name == name); However, the compiler outputs the following error: Error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.AnyAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, bool>)' and 'Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.AnyAsync<TSource>(System.Linq.IQueryable<TSource>, System.Linq

问题 I am using a LINQ query on a DbSet<T> : await _dbContext.Users.AnyAsync(u => u.Name == name); However, the compiler outputs the following error: Error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.AnyAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, bool>)' and 'Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.AnyAsync<TSource>(System.Linq.IQueryable<TSource>, System.Linq

问题 I am using a LINQ query on a DbSet<T> : await _dbContext.Users.AnyAsync(u => u.Name == name); However, the compiler outputs the following error: Error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.AnyAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, bool>)' and 'Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.AnyAsync<TSource>(System.Linq.IQueryable<TSource>, System.Linq

问题 I am using a LINQ query on a DbSet<T> : await _dbContext.Users.AnyAsync(u => u.Name == name); However, the compiler outputs the following error: Error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.AnyAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, bool>)' and 'Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.AnyAsync<TSource>(System.Linq.IQueryable<TSource>, System.Linq

问题 I am using a LINQ query on a DbSet<T> : await _dbContext.Users.AnyAsync(u => u.Name == name); However, the compiler outputs the following error: Error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.AnyAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, bool>)' and 'Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.AnyAsync<TSource>(System.Linq.IQueryable<TSource>, System.Linq

问题 In previous version of entity framework, one could recreate the database if the model changes, using some of the classes DropDatabseIfModelChanges and other related classes. In EF7 or EF Core i don't know how to do that. Run the migrations some times give problems and in the beginning of the project i need to change the models constantly. 回答1: There's currently no easy way to implement DropDatabseIfModelChanges in EFCore. EF6 worked by storing a snapshot of your model in the _

问题 I have a table called "LogBookSystemUsers" and I want to setup many to many functionality in EF Core 5. I almost have it working but the problem is my ID columns are named SystemUserId and LogBookId but when EF does the join it tries to use SystemUserID and LogBookID . This is my current configuration code: modelBuilder.Entity<SystemUser>() .HasMany(x => x.LogBooks) .WithMany(x => x.SystemUsers) .UsingEntity(x => { x.ToTable("LogBookSystemUsers", "LogBooks"); }); I tried this: modelBuilder