You can use Kros.KORM for creating queries and their materialization. Kros.KORM helps you put together desired query, that can return instances of objects populated from database by using foreach or linq.
Query for obtaining data
var people = database.Query<Person>()
.Select("p.Id", "FirstName", "LastName", "PostCode")
.From("Person JOIN Address ON (Person.AddressId = Address.Id)")
.Where("Age > @1", 18);
foreach (var person in people)
{
Console.WriteLine(person.FirstName);
}
For more information take a look at definition of IQuery.
Linq to Kros.KORM
Kros.KORM allows you to use Linq for creating queries. Basic queries are translated to SQL language.
Example
var people = database.Query<Person>()
.From("Person JOIN Address ON (Person.AddressId = Address.Id)")
.Where(p => p.LastName.EndsWith("ová"))
.OrderByDescending(p => p.Id)
.Take(5);
foreach (var person in people)
{
Console.WriteLine(person.FirstName);
}
Properties (not readonly or writeonly properties) are implicitly mapped to database fields with same name. When you want to map property to database field with different name use AliasAttribute. The same works for mapping POCO classes with database tables.
[Alias("Workers")]
private class Staff
{
[Alias("PK")]
public int Id { get; set; }
[Alias("Name")]
public string FirstName { get; set; }
[Alias("SecondName")]
public string LastName { get; set; }
}
private void StaffExample()
{
using (var database = new Database(_connection))
{
_command.CommandText = "SELECT PK, Name, SecondName from Workers";
using (var reader = _command.ExecuteReader())
{
var staff = database.ModelBuilder.Materialize<Staff>(reader);
}
}
}
When you need to have read-write properties independent of the database use NoMapAttribute.
[NoMap]
public int Computed { get; set; }
Convention model mapper
If you have different conventions for naming properties in POCO classes and fields in database, you can redefine behaviour of ModelMapper, which serves mapping POCO classes to database tables and vice versa.
Redefining mapping conventions example
Database.DefaultModelMapper.MapColumnName = (colInfo, modelType) =>
{
return string.Format("COL_{0}", colInfo.PropertyInfo.Name.ToUpper());
};
Database.DefaultModelMapper.MapTableName = (tInfo, type) =>
{
return string.Format("TABLE_{0}", type.Name.ToUpper());
};
using (var database = new Database(_connection))
{
_command.CommandText = "SELECT COL_ID, COL_FIRSTNAME from TABLE_WORKERS";
using (var reader = _command.ExecuteReader())
{
var people = database.ModelBuilder.Materialize<Person>(reader);
foreach (var person in people)
{
Console.WriteLine(person.FirstName);
}
}
}
Alternatively you can write your own implementation of IModelMapper.
Custom model mapper
Database.DefaultModelMapper = new CustomModelMapper();
If your POCO class is defined in external library, you can redefine mapper, so it can map properties of the model to desired database names.
External class mapping example
var externalPersonMap = new Dictionary<string, string>() {
{ nameOf(ExternalPerson.oId), "Id" },
{ nameOf(ExternalPerson.Name), "FirstName" },
{ nameOf(ExternalPerson.SecondName), "LastName" }
};
Database.DefaultModelMapper.MapColumnName = (colInfo, modelType) =>
{
if (modelType == typeof(ExternalPerson))
{
return externalPersonMap[colInfo.PropertyInfo.Name];
}
else
{
return colInfo.PropertyInfo.Name;
}
};
using (var database = new Database(_connection))
{
var people = database.Query<ExternalPerson>();
foreach (var person in people)
{
Console.WriteLine($"{person.oId} : {person.Name}-{person.SecondName}");
}
}
Configuration by data annotation attributes is OK in many scenarios. However, there are scenarios where we want to have a model definition and mapping it to a database separate.
For example, if you want to have entities in domain layer and mapping in infrastructure layer.
For these scenarios you can derive database configuration from DatabaseConfigurationBase.
public class User
{
public int Id { get; set; }
public string Title { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string FullName => FirstName + " " + LastName;
public Address Address { get; set; }
public IEmailService EmailService { get; set; }
}
public class DatabaseConfiguration : DatabaseConfigurationBase
{
public override void OnModelCreating(ModelConfigurationBuilder modelBuilder)
{
modelBuilder.Entity<User>()
.HasTableName("Users")
.HasPrimaryKey(entity => entity.Id).AutoIncrement(AutoIncrementMethodType.Custom)
.UseConverterForProperties<string, NullToEmptyStringConverter>()
.Property(entity => entity.Title).IgnoreConverter()
.Property(entity => entity.FirstName).HasColumnName("Name")
.Property(entity => entity.FullName).NoMap()
.Property(entity => entity.Addresses).UseConverter<AddressConverter>()
.Property(entity => entity.EmailService).InjectValue(() => new EmailService())
.Property(entity => entity.IsGenerated).UseValueGeneratorOnInsert<RandomGenerator>();
}
}
And use IDatabaseBuilder for creating KORM instance.
var database = Database
.Builder
.UseConnection(connection)
.UseDatabaseConfiguration<DatabaseConfiguration>()
.Build();
If converter is used for property type (UseConverterForProperties) and also for specific property of that type (UseConverter),
the latter one has precedence.
Global query filter
In many cases, we want to define a global filter to apply to each query. For example: ParentId = 1, UserId = ActiveUser.Id, etc.
You can configurate query filter in DatabaseConfiguration class.
public class DatabaseConfiguration : DatabaseConfigurationBase
{
public override void OnModelCreating(ModelConfigurationBuilder modelBuilder)
{
modelBuilder.Table("Document")
.UseQueryFilter<Document>(entity => entity.UserId == ActiveUser.Id && entity.ParentId == 1);
}
}
KORM will automatically add a condition ((UserId = @__Dqf1) AND (ParentId = @__Dqf2)) when calling any query using Query<Document>().
Except for direct sql calls like _database.Query<Document>().Sql("SELECT * FROM DOCUMENT").
:warning: Configuration modelBuilder.Table("Documents") is applied for all entities mapped to table Documents (for example Document, DocumentDto, DocumentInfo, ...).
Ignoring global filters
If I need to call a query without these conditions, I must explicitly say:
If you need to name your column or table with a name that the server has among the reserved words (for example, Order), you must ensure that these names are quoted in queries.
If the queries are generated by KORM, then you must explicitly specify delimiters in the DatabaseConfiguration.
public class DatabaseConfiguration : DatabaseConfigurationBase
{
public override void OnModelCreating(ModelConfigurationBuilder modelBuilder)
{
modelBuilder.UseIdentifierDelimiters(Delimiters.SquareBrackets);
}
}
Converters
Data type of column in database and data type of property in your POCO class may differ. Some of these differences are automatically solved by Kros.KORM, for example double in database is converted to int in your model, same as int in database to enum in model, etc.
For more complicated conversion Kros.KORM offers possibility similar to data binding in WPF, where IValueConverter is used.
Imagine you store a list of addresses separated by some special character (for example #) in one long text column, but the property in your POCO class is list of strings.
Let's define a converter that can convert string to list of strings.
public class AddressesConverter : IConverter
{
public object Convert(object value)
{
var ret = new List<string>();
if (value != null)
{
var address = value.ToString();
var addresses = address.Split('#');
ret.AddRange(addresses);
}
return ret;
}
public object ConvertBack(object value)
{
return string.Join("#", (value as List<string>));
}
}
And now you can set this converter for your property using attribute or fluent configuration.
[Converter(typeof(AddressesConverter))]
public List<string> Addresses { get; set; }
Value generators
Value generators are used to generate column values. KORM contains some predefined generators but you can create your own.
For this purpose exists IValueGenerator interface which your class must implement.
public interface IValueGenerator
{
object GetValue();
}
Here is an example of custom value generator:
private class AutoIncrementValueGenerator : IValueGenerator
{
public object GetValue() => 123;
}
For using value generators you can use these three methods in DatabaseConfiguration:
.UseValueGeneratorOnInsert<YourGenerator>() - values will be generated on insert to the database.
.UseValueGeneratorOnUpdate<YourGenerator>() - values will be generated on update to the database.
.UseValueGeneratorOnInsertOrUpdate<YourGenerator>() - values will be generated on insert and update to the database.
Currently predefined value generators:
CurrentTimeValueGenerator - Generator generates date and time that are set to the current Coordinated Universal Time (UTC).
Ignoring value generators
If you need to perfrom a database operation without the use of value generators you can do so by passing parameter ignoreValueGenerators in either of the commit methods. This will ensure that all operations within commited transaction will be completed without supplementing values from value generators.
If you want to do some special action right after materialisation is done (for example to do some calculations) or you want to get some other values from source reader, that can not by processed automatically, your class should implement interface IMaterialize.
You can do whatever you need in method OnAfterMaterialize.
For example, if you have three int columns for date in database (Year, Month and Day) but in your POCO class you have only one date property, you can solve it as follows:
[NoMap]
public DateTime Date { get; set; }
public void OnAfterMaterialize(IDataRecord source)
{
var year = source.GetInt32(source.GetOrdinal("Year"));
var month = source.GetInt32(source.GetOrdinal("Month"));
var day = source.GetInt32(source.GetOrdinal("Day"));
this.Date = new DateTime(year, month, day);
}
Property injection
Sometimes you might need to inject some service to your model, for example calculator or logger. For these purposes Kros.KORM offers IInjectionConfigurator, that can help you with injection configuration.
Let's have properties in model
[NoMap]
public ICalculationService CalculationService { get; set; }
[NoMap]
public ILogger Logger { get; set; }
For materialisation Kros.KORM uses IModelFactory, that creates factory for creating and filling your POCO objects.
By default DynamicMethodModelFactory is implemented, which uses dynamic method for creating delegates.
If you want to try some other implementation (for example based on reflexion) you can redefine property Database.DefaultModelFactory.
Database.DefaultModelFactory = new ReflectionModelfactory();
Committing of changes
You can use Kros.KORM also for editing, adding or deleting records from database. IdDbSet is designed for that.
Records to edit or delete are identified by the primary key. You can set primary key to your POCO class by using Key attribute.
[Key()]
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
Inserting records to database
public void Insert()
{
using (var database = new Database(_connection))
{
var people = database.Query<Person>().AsDbSet();
people.Add(new Person() { Id = 1, FirstName = "Jean Claude", LastName = "Van Damme" });
people.Add(new Person() { Id = 2, FirstName = "Sylvester", LastName = "Stallone" });
people.CommitChanges();
}
}
Kros.KORM supports bulk inserting, which is one of its best features. You add records to DbSet standardly by method Add, but for committing to database use method BulkInsert instead of CommitChanges.
var people = database.Query<Person>().AsDbSet();
foreach (var person in dataForImport)
{
people.Add(person);
}
people.BulkInsert();
Kros.KORM supports also bulk update of records, you can use BulkUpdate method.
var people = database.Query<Person>().AsDbSet();
foreach (var person in dataForUpdate)
{
people.Edit(person);
}
people.BulkUpdate();
This bulk way of inserting or updating data is several times faster than standard inserts or updates.
For both of bulk operations you can provide data as an argument of method. The advantage is that if you have a specific enumerator, you do not need to spill data into memory.
Primary key generating
Kros.KORM supports generating of primary keys for inserted records.
Support two types of generating:
Custom
KORM supports 'Int32' and 'Int64' generators. Primary key property in POCO class must be decorated by Key attribute
and its property AutoIncrementMethodType must be set to Custom.
public class User
{
[Key(autoIncrementMethodType: AutoIncrementMethodType.Custom)]
public int Id { get; set; }
}
Kros.KORM generates primary key for every inserted record, that does not have value for primary key property.
For generating primary keys implementations of IIdGenerator
are used.
The names of internal generators are the same as table names, for which the values are generated. But this can be explicitly
set to some other name. It can be used for example when one generated sequence of numbers need to be used in two tables.
public class User
{
[Key(autoIncrementMethodType: AutoIncrementMethodType.Custom, generatorName: "CustomGeneratorName")]
public int Id { get; set; }
}
// Or using fluent database configuration.
public class DatabaseConfiguration : DatabaseConfigurationBase
{
public override void OnModelCreating(ModelConfigurationBuilder modelBuilder)
{
modelBuilder.Entity<User>()
.HasPrimaryKey(entity => entity.Id).AutoIncrement(AutoIncrementMethodType.Custom, "CustomGeneratorName");
}
}
Identity
When you set AutoIncrementMethodType to Identity, Kros.KORM use MsSql Identity for generating primary key and fill generated keys into entity.
CREATE TABLE [dbo].[Users](
[Id] [bigint] IDENTITY(1,1) NOT NULL,
[FIrstName] [nvarchar](50) NULL,
CONSTRAINT [PK_Users] PRIMARY KEY CLUSTERED
(
[Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
[Key(autoIncrementMethodType: AutoIncrementMethodType.Identity)]
public long Id { get; set; }
When you call dbSet.CommitChanges(), Kros.KORM fill generated keys into entity. Unfortunately, doesn't know it when you call a method dbSet.BulkInsert().
Editing records in database
public void Edit()
{
using (var database = new Database(_connection))
{
var people = database.Query<Person>().AsDbSet();
foreach (var person in people)
{
person.LastName += "ová";
people.Edit(person);
}
people.CommitChanges();
}
}
Deleting records from database
public void Delete()
{
using (var database = new Database(_connection))
{
var people = database.Query<Person>().AsDbSet();
people.Delete(people.FirstOrDefault(x => x.Id == 1));
people.Delete(people.FirstOrDefault(x => x.Id == 2));
people.CommitChanges();
}
}
Deleting records by Ids or condition
public void Delete()
{
using (var database = new Database(_connection))
{
var people = database.Query<Person>().AsDbSet();
people.Delete(1);
people.Delete(p => p.ParentId == 10);
people.CommitChangesAsync();
}
}
Upsert record by it's primary key
Kros.KORM supports upserting records based on primary key match.
This can be handy when you know the primary key (or composite primary key) of the record but you can not be sure if it already exists in database.
Given (CompanyId, UserId) is composite primary key for UserRole table:
var admin = new UserRole { CompanyId = 1, UserId = 11, Role = "Admin" };
var owner = new UserRole { CompanyId = 1, UserId = 11, Role = "Owner" };
var user = new UserRole { CompanyId = 2, UserId = 22, Role = "User" };
using (var database = new Database(_connection))
{
var userRoles = database.Query<UserRole>().AsDbSet();
userRoles.Add(admin);
userRoles.CommitChanges();
var userRoles = database.Query<UserRole>().AsDbSet();
userRoles.Upsert(owner); // this will update admins UserRole to owner
userRoles.Upsert(user); // this will insert user
userRoles.CommitChanges();
}
Upsert record by custom columns match
It is possible to upsert records by match of non PK columns.
!!! Use this with caution. This updates all records with matching provided columns !!!
var admin1 = new UserRole { Id = 1, InternalUserNo = 11, Role = "Admin" };
var admin2 = new UserRole { Id = 2, InternalUserNo = 12, Role = "Admin" };
var owner1 = new UserRole { Id = 3, InternalUserNo = 11, Role = "Owner" };
using (var database = new Database(_connection))
{
var userRoles = database.Query<UserRole>().AsDbSet();
userRoles.Add(admin1);
userRoles.CommitChanges();
var userRoles = database.Query<UserRole>().AsDbSet()
.WithCustomUpsertConditionColumns(nameof(UserRole.InternalUserNo));
userRoles.Upsert(admin2); // this will insert new admin with internalUserNo = 12
userRoles.Upsert(owner1); // this will update user with internalUserNo = 11 to Owner
userRoles.CommitChanges();
}
Explicit transactions
By default, changes of a DbSet are committed to database in a transaction. If committing of one record fails, rollback of transaction is executed.
Sometimes you might come to situation, when such implicit transaction would not meet your requirements. For example you need to commit changes to two tables as an atomic operation. When saving changes to first of tables is not successful, you want to discard changes to the other table. Solution of that task is easy with explicit transactions supported by Kros.KORM. See the documentation of BeginTransaction.
using (var transaction = database.BeginTransaction())
{
var invoicesDbSet = database.Query<Invoice>().AsDbSet();
var itemsDbSet = database.Query<Item>().AsDbSet();
try
{
invoicesDbSet.Add(invoices);
invoicesDbSet.CommitChanges();
itemsDbSet.Add(items);
itemsDbSet.CommitChanges();
transaction.Commit();
}
catch
{
transaction.Rollback();
}
}
Simplify Adding, Deleting and Editing records
For simplifying calling methods (Add, Edit, Delete) use extension methods from IDatabaseExtensions class.
Kros.KORM offers special execute commands for SQL databases, that inserts provided simple data into temp table and
then executes some specified action using those temporary data.
You can find these extension methods in IDatabaseExtensions class.
database.ExecuteWithTempTable<TValue>(IEnumerable<TValue> values, action);
await database.ExecuteWithTempTableAsync<TValue>(IEnumerable<TValue> values, function);
database.ExecuteWithTempTable<TKey, TValue>(IDictionary<TKey, TValue> values, action);
await database.ExecuteWithTempTable<TKey, TValue>(IDictionary<TKey, TValue> values, function);
T database.ExecuteWithTempTable<T, TValue> (IEnumerable<TValue> values, action);
await T database.ExecuteWithTempTable<T, TValue> (IEnumerable<TValue> values, function);
T database.ExecuteWithTempTable<T, TKey, TValue> (IDictionary<TKey, TValue> values, action);
await T database.ExecuteWithTempTable<T,TKey, TValue> (IDictionary<TKey, TValue> values, function);
public class Person
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
var ids = new List<int>(){ 0, 1, 2, 3 };
_database.ExecuteWithTempTable(ids, (database, tableName)
=> database.Query<Person>()
.From($"PERSON AS P INNER JOIN {tableName} AS T ON (P.Id = T.Value)")
.ToList());
public class IdDto
{
public IdDto(int id)
{
Id = id;
}
public int Id { get; set; }
}
var ids = new List<IdDto>(){ new IdDto(0), new IdDto(1), new IdDto(2), new IdDto(3) };
_database.ExecuteWithTempTable(ids, (database, tableName)
=> database.Query<Person>()
.Select("P.*")
.From($"PERSON AS P INNER JOIN {tableName} AS T ON (P.Id = T.Id)")
.ToList());
SQL commands executing
Kros.KORM supports SQL commands execution. There are three types of commands:
ExecuteNonQuery for commands that do not return value (DELETE, UPDATE, ...)
private Database _database = new Database(new SqlConnection("connection string"));
// to work with command parameters you can use CommandParameterCollection
var parameters = new CommandParameterCollection();
parameters.Add("@value", "value");
parameters.Add("@id", 10);
parameters.Add("@type", "DateTime");
_database.ExecuteNonQuery("UPDATE Column = @value WHERE Id = @id AND Type = @type", parameters);
// or you can send them directly via params array
_database.ExecuteNonQuery("UPDATE Column = @value WHERE Id = @id AND Type = @type", "value", 10, "DateTime");
ExecuteScalar for commands that return only one value (SELECT)
ExecuteStoredProcedure for executing of stored procedures. Stored procedure may return scalar value or list of values or it can return data in output parameters.
Execution of stored procedure example
public class Person
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime BDay { get; set; }
}
private Database _database = new Database(new SqlConnection("connection string"));
// Stored procedure returns a scalar value.
int intResult = _database.ExecuteStoredProcedure<int>("ProcedureName");
DateTime dateResult = _database.ExecuteStoredProcedure<DateTime>("ProcedureName");
// Stored procedure sets the value of output parameter.
var parameters = new CommandParameterCollection();
parameters.Add("@param1", 10);
parameters.Add("@param2", DateTime.Now);
parameters.Add("@outputParam", null, DbType.String, ParameterDirection.Output);
_database.ExecuteStoredProcedure<string>("ProcedureName", parameters);
Console.WriteLine(parameters["@outputParam"].Value);
// Stored procedure returns complex object.
Person person = _database.ExecuteStoredProcedure<Person>("ProcedureName");
// Stored procedure returns list of complex objects.
IEnumerable<Person> persons = _database.ExecuteStoredProcedure<IEnumerable<Person>>("ProcedureName");
CommandTimeout support
If you want to execute time-consuming command, you will definitely appreciate CommandTimeout property of transaction. See the documentation of BeginTransaction.
Warning: You can set CommandTimeout only for main transaction, not for nested transactions. In that case CommandTimout of main transaction will be used.
Option for post-migration actions and post-migration database views refresh with an option to accept the script ID up to which actions will be executed after migration is available. The default script RefreshViews.sql for refreshing views is in resources.
Action will be executed only if the ID of the latest script of the migration is less than or equal to the user-defined ID. If the ID is not defined, the action will execute regardless.
const long scriptId = 20251912010;
builder.Services.AddKorm(builder.Configuration)
.AddKormMigrations(options =>
{
var assembly = Assembly.GetEntryAssembly();
options.AddAssemblyScriptsProvider(assembly, "CompanyStruct.SqlScripts");
options.AddRefreshViewsAction();
options.AddAfterMigrationAction(async (database, id) =>
{
if (id <= scriptId)
{
await database.ExecuteNonQueryAsync("INSERT ...");
}
});
})
.Migrate();
Record types
KORM supports a new record type for model definition.
public record Person(int Id, string FirstName, string LastName);
using var database = new Database(new SqlConnection("connection string"));
foreach (Person person = database.Query<Person>())
{
Console.WriteLine($"{person.Id}: {person.FirstName} - {person.LastName}");
}
The same features as for "standard" class-es are supported. Converters, name mapping and value injection. It is possible to use fluent notation, but also using attributes.
To use attribute notation, you must use syntax with property: keyword.
public record Person(int Id, [property: Alias("FirstName")]string Name);
Materializing record types is a bit faster than with property-filled classes.
1000 rows of InMemoryDbReader:
Method
Mean
Error
StdDev
RecordTypes
301.50 μs
5.07 μs
7.11 μs
ClassTypes
458.10 μs
7.13 μs
6.68 μs
Logging
Kros.KORM offers the ability to log each generated and executed query. All you have to do is add this line to your source code.
Database.Log = Console.WriteLine;
Supported database types
Kros.KORM uses its own QueryProvider to execute query in a database. ISqlExpressionVisitor transforms IQuery to SELECT command specific for each supported database engine.
MsAccess is suported from version 2.4 in Kros.KORM.MsAccess library. If you need to work with MS Access database, you have to refer this library in your project and register MsAccessQueryProviderFactory.
MsAccessQueryProviderFactory.Register();
Current version of Kros.KORM suports databases MS ACCESS and MS SQL.
