I replaced the MySQL.Data package with Dapper. To fetch one user from the database all I have to do now is
public Task<User> GetUser(string username)
{
using IDbConnection databaseConnection = new MySqlConnection("connectionString");
DynamicParameters parameters = new DynamicParameters();
parameters.Add("#username", username, DbType.String);
return databaseConnection.QueryFirstOrDefaultAsync<User>(
"SELECT * FROM person WHERE username = #username",
parameters);
}
but I would like to add some trace level logging. Is there a way I can fetch the query string before executing it?
Create your own IDbCommand which would wrap your real IDbCommand and log what you want to intercept.
But since Dapper creates the IDbCommand automatically, you also have to create your own IDbConnection (see CreateCommand below) which would wrap your real IDbConnection and in case would use your own IDbCommand.
Example:
/// <summary>
/// This is just a wrapper around IDbConnection,
/// which allows us to build a wrapped IDbCommand for logging/debugging
/// </summary>
public class InterceptedDbConnection : IDbConnection
{
private readonly IDbConnection _conn;
public InterceptedDbConnection(IDbConnection connection)
{
_conn = connection;
}
public string ConnectionString { get => _conn.ConnectionString; set => _conn.ConnectionString = value; }
public int ConnectionTimeout => _conn.ConnectionTimeout;
public string Database => _conn.Database;
public ConnectionState State => _conn.State;
public IDbTransaction BeginTransaction() => _conn.BeginTransaction();
public IDbTransaction BeginTransaction(IsolationLevel il) => _conn.BeginTransaction(il);
public void ChangeDatabase(string databaseName) => _conn.ChangeDatabase(databaseName);
public void Close() => _conn.Close();
public IDbCommand CreateCommand()
{
// Wrap real command under InterceptedDbCommand
IDbCommand underlyingCommand = _conn.CreateCommand();
return new InterceptedDbCommand(underlyingCommand);
// you could also save this into a "LastCommand" to expose it
// and explore parameter types that Dapper used
}
public void Dispose() => _conn.Dispose();
public void Open() => _conn.Open();
}
/// <summary>
/// This is just a wrapper around IDbCommand,
/// which allows us to log queries
/// or inspect how Dapper is passing our Parameters
/// </summary>
public class InterceptedDbCommand : IDbCommand
{
private readonly IDbCommand _cmd;
public InterceptedDbCommand(IDbCommand command)
{
_cmd = command;
}
public string CommandText { get => _cmd.CommandText; set => _cmd.CommandText = value; }
public int CommandTimeout { get => _cmd.CommandTimeout; set => _cmd.CommandTimeout = value; }
public CommandType CommandType { get => _cmd.CommandType; set => _cmd.CommandType = value; }
public IDbConnection Connection { get => _cmd.Connection; set => _cmd.Connection = value; }
public IDataParameterCollection Parameters => _cmd.Parameters;
public IDbTransaction Transaction { get => _cmd.Transaction; set => _cmd.Transaction = value; }
public UpdateRowSource UpdatedRowSource { get => _cmd.UpdatedRowSource; set => _cmd.UpdatedRowSource = value; }
public void Cancel() => _cmd.Cancel();
public IDbDataParameter CreateParameter() => _cmd.CreateParameter();
public void Dispose() => _cmd.Dispose();
public void Prepare() => _cmd.Prepare();
public int ExecuteNonQuery()
{
// TODO: Log _cmd.CommandText + _cmd.Parameters
return _cmd.ExecuteNonQuery();
}
public IDataReader ExecuteReader()
{
// TODO: Log _cmd.CommandText + _cmd.Parameters
return _cmd.ExecuteReader();
}
public IDataReader ExecuteReader(CommandBehavior behavior)
{
// TODO: Log _cmd.CommandText + _cmd.Parameters
return _cmd.ExecuteReader(behavior);
}
public object ExecuteScalar()
{
// TODO: Log _cmd.CommandText + _cmd.Parameters
return _cmd.ExecuteScalar();
}
}
Last, just replace your connection by the wrapped one:
IDbConnection databaseConnection = new InterceptedDbConnection(MySqlConnection("connectionString"));
I need to pass the DbConnection to my class.
For that I am using the NSubstitute.
But when I run the test the following error occurs:
"System.NullReferenceException: Object reference not set to an instance of an object. Dapper"
My Test
public class SceneApplicationServiceTest
{
private readonly DbConnection _connection = Substitute.For<DbConnection>();
ISceneApplicationService _sceneApplicationService;
public SceneApplicationServiceTest()
{
_sceneApplicationService = new SceneApplicationService(_connection);
}
[Fact]
public async Task ShouldBePossibleSuccessfullyGetByProgramScript()
{
const long programId = 1;
const string scriptId = "2";
await _sceneApplicationService.GetByProgramScript(programId, scriptId);
await _sceneApplicationService.Received(1).GetByProgramScript(programId, scriptId);
}
}
My method
public class SceneApplicationService : ISceneApplicationService
{
private readonly DbConnection _connection;
public SceneApplicationService(DbConnection connection)
{
_connection = connection;
}
public async Task<IEnumerable<LegacySceneResponse>> GetByProgramScript(long programId, string scriptId)
{
object parameters = new
{
CodigoPrograma = programId,
CodigoRoteiro = scriptId
};
if (!ObjectValidation.IsInvalidAnyNullOrEmpty(parameters)) ;
return await _connection.QueryAsync<LegacySceneResponse>(GetScenesByScriptAndProgram.Query, parameters);
}}
The error occurs when the test tries to run the "QueryAsync"
Any ideas?
look here, its the moq for dapper extensions:
https://github.com/UnoSD/Moq.Dapper
QueryAsync is the extension method from Dapper nuget.
Using EntityFramework, I have an auto-generated file with:
namespace Chaos.Data
{
public partial class ChaosModel : OpenAccessContext, IChaosModelUnitOfWork
{
private static string connectionStringName = #"ChaosLibraryConnection";
private static BackendConfiguration backend = GetBackendConfiguration();
private static MetadataSource metadataSource = XmlMetadataSource.FromAssemblyResource("EntitiesModel.rlinq");
public ChaosModel()
:base(connectionStringName, backend, metadataSource)
{ }
public ChaosModel(string connection)
:base(connection, backend, metadataSource)
{ }
......................
In the WCF Service, I am using:
namespace Chaos.DataService
{
[ServiceContract]
public class ChaosService
{
[OperationContract]
public IEnumerable<Encountertime> GetEncounterTimes(DateTime? encountertime)
{
if (encountertime == null) return null;
using (var context = new ChaosModel())
{
var query = from et in context.Encountertimes
where et.Tencounter.Date == ((DateTime)encountertime).Date
select et;
var result = context.CreateDetachedCopy(query.ToList());
return result;
}
}
.............................
How can I make the WCF service on startup execute a method (once) that will return a new connection string so that I can change the calls to ChaosModel() to:
using (var context = new ChaosModel(connectionString))
(I am looking for a way to add a static constructor within the WCF service--or something better?).
(The method will determine the network I am on and construct an appropriate connection string to the network server.)
Note: I can make no changes to the auto-generated Entity file.
Use static constructor.
[ServiceContract]
public class ChaosService
{
private static string connectionString;
static ChaosService(){
connectionString = your logic...
}
[OperationContract]
public IEnumerable<Encountertime> GetEncounterTimes(DateTime? encountertime)
{
using (var context = new ChaosModel(connectionString))
{
...
}
}
}
or eventually a singleton pattern:
public class ConnectionInfo
{
public string ConnectionString { get; private set; }
private ConnectionInfo()
{
var connectionstring = string.Empty;
//some logic
this.ConnectionString = connectionstring;
}
private static ConnectionInfo current;
public static ConnectionInfo Current {
get {
if (current != null)
current = new ConnectionInfo();
return current;
}
}
}
[OperationContract]
public IEnumerable<Encountertime> GetEncounterTimes(DateTime? encountertime)
{
using (var context = new ChaosModel(ConnectionInfo.Current.ConnectionString))
{
...
}
}
First of all I read this on an article - which basically tells me I should not be using a singleton at all -
Most commonly, singletons don't allow any parameters to be specified when creating the instance - as otherwise a second request for an instance but with a different parameter could be problematic! (If the same instance should be accessed for all requests with the same parameter, the factory pattern is more appropriate.)
Since I need parameters, and same instances with same parameters - I concluded I need a factory pattern.
But I was unable to find a good factory pattern implementation anywhere.
Kindly direct me if you find any good c# singleton factory pattern implementation with parameters
Ok I am going to try and be very specific here... hope this explains my situation.
Alternate methods are most welcome. I just combined a lot of implementations - my understanding may be off.
So I have a class 'A'. It is a class used to connect to a database - Database connection.
The connection needs 4 parameters & the constraints are:
I need to have multiple connections possible - with different databases (parameters differ)
I need only 1 instance of a specific connection - a singleton with parameters which are same (in my understanding)
I will need a factory model as per the article mentioned above and also to limit the number of connections, close the connection after a timeout etc.
On this basis I need a singleton factory with paramenters/arguements... I assume
So the class A is going to look something like this
<which access modifier ?> Class A {
private Class A(string hostname, string port, string username, string pw_hash) {
//create a new instance with the specified parameters
}
//other methods on the connection
protected void close() {
//close the connection
}
}
public class AFactory//should it inherit class A?? {
private IList<A> connections = new List<A>();
private AFactory()
{
//do something
}
private static readonly Lazy<AFactory> lazy
= new Lazy<AFactory>(() => new AFactory());
public static AFactory Instance { get { return lazy.Value; } }
public A getA(string hostname, string service, string username, string pw_hash)
{
foreach (A a in A)
{
if (a.hostname == hostname && a.service == service && a.username == username)
return a;
}
A d = new A(hostname, service, username, pw_hash);
connections.Add(d);
return d;
}
Now this works well and good as long as the class A constructor is public - but It kind of defeats the purpose of a singleton.
What do I need to do to get this code to work.
I need only 1 instance of class A for the specified parameters.
Thanks
Indrajit
Factory is used to generate object rather than manage object. I think a DB connection manager is more suitable in your situation. You can declare the manager as singleton. For individual connection you can use internal class/struct.
See below example:
class DBConnectionManager
{
struct Connection
{
public string Hostname;
public string ServerName;
public string UserName;
public string Password;
public void Connect()
{
}
public void Close()
{
}
}
private static s_instance;
public static DBConnectionManager Instance
{
get {return s_instance; }
}
private List<Connection> m_connections;
public Connection GetConnection(string hostname, string serverName, string userName, string password)
{
// if already exist in m_connections
// return the connection
// otherwise create new connection and add to m_connections
}
public void CloseConnection(string hostname, string serverName, string userName, string password)
{
// if find it in m_connections
// then call Close()
}
public void CloseAll()
{
//
}
}
So I have done this and it works... can you tell me if it is correct. And also is it Thread-Safe?
public Class A
{
private A(string hostname, string port, string username, string pw_hash) {
//create a new instance with the specified parameters
}
//other methods on the connection
protected void close() {
//close the connection
}
public class AFactory
{
private IList<A> connections = new List<A>();
private AFactory()
{
//do something
}
private static readonly Lazy<AFactory> lazy
= new Lazy<AFactory>(() => new AFactory());
public static AFactory Instance { get { return lazy.Value; } }
public A getA(string hostname, string service, string username, string pw_hash)
{
foreach (A a in connections)
{
if (a.hostname == hostname && a.service == service && a.username == username)
return a;
}
A d = new A(hostname, service, username, pw_hash);
connections.Add(d);
return d;
}
}
}
I am using it like this:
A.AFactory fact = A.AFactory.Instance;
A conn = fact.getA(a, b, c, d);
A conn2 = fact.getA(e, f, g, h);
Is there something glaringly wrong with this implementation?
you could try this:
public static class Singlett<Param,T>
where T : class
{
static volatile Lazy<Func<Param, T>> _instance;
static object _lock = new object();
static Singlett()
{
}
public static Func<Param, T> Instance
{
get
{
if (_instance == null)
{
_instance = new Lazy<Func<Param, T>>(() =>
{
lock (Singlett<Param,T>._lock)
{
try
{
ConstructorInfo constructor = null;
Type[] methodArgs = { typeof(Param) };
constructor = typeof(T).GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, null, methodArgs, null);// Binding flags excludes public constructors.
if (constructor == null)
{
constructor = typeof(T).GetConstructor(BindingFlags.Public, null, methodArgs, null);
if (constructor == null)
return delegate(Param o) { return (T)Activator.CreateInstance(typeof(T), new object[] { o }); };
}
return delegate(Param o) { return (T)constructor.Invoke(new object[] { o }); };
}
catch (Exception exception)
{
throw exception;
}
}
});
}
return _instance.Value;
}
}
}
then to use it:
instead of
int i = 10;
MyClass class = new MyClass(i);
you can write:
int i = 10;
MyClass class = Singlett<int,MyClass>.Instance(i);
Try this:
This interface is exposed from the factory initializer and contains the exposed methods and properties.
public interface IDatabase
{
string ConnectionString { get; set; }
IDataReader ExecuteSql(string sql);
}
Factory base abstract class where you can perform common features to different types of database factories.
public abstract class FactoryBase
{
public FactoryBase() { }
public abstract IDatabase GetDataLayer();
}
Concrete sql class that contains your calls. Have a look at the ExecuteSql method. The connection is self contained in the command so you don't have to worry about opening and closing and disposing of it.
public class SQL : IDatabase
{
private string m_ConnectionString = string.Empty;
public string ConnectionString
{
get { return m_ConnectionString; }
set { m_ConnectionString = value; }
}
public IDataReader ExecuteSql(string sql)
{
using (var command = new SqlCommand(sql, new SqlConnection(ConnectionString)) { CommandType = CommandType.Text, CommandText = sql, CommandTimeout = 0 })
{
if (command.Connection.State != ConnectionState.Open) command.Connection.Open();
return command.ExecuteReader();
}
}
}
Sql factory class that creates an instance of the Sql concrete class.
class SQLFactory : FactoryBase
{
public override IDatabase GetDataLayer()
{
return new SQL();
}
}
The factory initializer class that a developer will use to pass in a type of factory and it will return the IDatabase.
public static class FactoryInitializer
{
public static IDatabase LoadFactory<T>(string connectionstring) where T : FactoryBase, new()
{
var factory = new T();
var data = factory.GetDataLayer();
data.ConnectionString = connectionstring;
return data;
}
}
Then use it as:
var factory = FactoryInitializer.LoadFactory<SQLFactory>(connectionString);
factory.ExecuteSql("SELECT ...");
You can then create may be an OracleFactory and an Oracle concrete class and use it the same way.
I've been playing with Dapper, but I'm not sure of the best way to handle the database connection.
Most examples show the connection object being created in the example class, or even in each method. But it feels wrong to me to reference a connection string in every clss, even if it's pulling from the web.config.
My experience has been with using a DbDataContext or DbContext with Linq to SQL or Entity Framework, so this is new to me.
How do I structure my web apps when using Dapper as my Data Access strategy?
Update: clarification from MarredCheese's comment:
"No need to use a using statement. Dapper will automatically open,
close, and dispose of the connection for you." That's not correct.
Dapper will automatically open closed connections, and it will
automatically close connections that it auto-opened, but it will not
automatically dispose of connections. Marc Gravell and Eric Lippert
both advocate using using with Dapper here.
Microsoft.AspNetCore.All: v2.0.3 | Dapper: v1.50.2
I am not sure if I am using the best practices correctly or not, but I am doing it this way, in order to handle multiple connection strings.
It's easy if you have only 1 connection string
Startup.cs
using System.Data;
using System.Data.SqlClient;
namespace DL.SO.Project.Web.UI
{
public class Startup
{
public IConfiguration Configuration { get; private set; }
// ......
public void ConfigureServices(IServiceCollection services)
{
// Read the connection string from appsettings.
string dbConnectionString = this.Configuration.GetConnectionString("dbConnection1");
// Inject IDbConnection, with implementation from SqlConnection class.
services.AddTransient<IDbConnection>((sp) => new SqlConnection(dbConnectionString));
// Register your regular repositories
services.AddScoped<IDiameterRepository, DiameterRepository>();
// ......
}
}
}
DiameterRepository.cs
using Dapper;
using System.Data;
namespace DL.SO.Project.Persistence.Dapper.Repositories
{
public class DiameterRepository : IDiameterRepository
{
private readonly IDbConnection _dbConnection;
public DiameterRepository(IDbConnection dbConnection)
{
_dbConnection = dbConnection;
}
public IEnumerable<Diameter> GetAll()
{
const string sql = #"SELECT * FROM TABLE";
// No need to use using statement. Dapper will automatically
// open, close and dispose the connection for you.
return _dbConnection.Query<Diameter>(sql);
}
// ......
}
}
Problems if you have more than 1 connection string
Since Dapper utilizes IDbConnection, you need to think of a way to differentiate different database connections.
I tried to create multiple interfaces, 'inherited' from IDbConnection, corresponding to different database connections, and inject SqlConnection with different database connection strings on Startup.
That failed because SqlConnection inherits from DbConnection, and DbConnection inplements not only IDbConnection but also Component class. So your custom interfaces won't be able to use just the SqlConnection implenentation.
I also tried to create my own DbConnection class that takes different connection string. That's too complicated because you have to implement all the methods from DbConnection class. You lost the help from SqlConnection.
What I end up doing
During Startup, I loaded all connection string values into a dictionary. I also created an enum for all the database connection names to avoid magic strings.
I injected the dictionary as Singleton.
Instead of injecting IDbConnection, I created IDbConnectionFactory and injected that as Transient for all repositories. Now all repositories take IDbConnectionFactory instead of IDbConnection.
When to pick the right connection? In the constructor of all repositories! To make things clean, I created repository base classes and have the repositories inherit from the base classes. The right connection string selection can happen in the base classes.
DatabaseConnectionName.cs
namespace DL.SO.Project.Domain.Repositories
{
public enum DatabaseConnectionName
{
Connection1,
Connection2
}
}
IDbConnectionFactory.cs
using System.Data;
namespace DL.SO.Project.Domain.Repositories
{
public interface IDbConnectionFactory
{
IDbConnection CreateDbConnection(DatabaseConnectionName connectionName);
}
}
DapperDbConenctionFactory - my own factory implementation
namespace DL.SO.Project.Persistence.Dapper
{
public class DapperDbConnectionFactory : IDbConnectionFactory
{
private readonly IDictionary<DatabaseConnectionName, string> _connectionDict;
public DapperDbConnectionFactory(IDictionary<DatabaseConnectionName, string> connectionDict)
{
_connectionDict = connectionDict;
}
public IDbConnection CreateDbConnection(DatabaseConnectionName connectionName)
{
string connectionString = null;
if (_connectDict.TryGetValue(connectionName, out connectionString))
{
return new SqlConnection(connectionString);
}
throw new ArgumentNullException();
}
}
}
Startup.cs
namespace DL.SO.Project.Web.UI
{
public class Startup
{
// ......
public void ConfigureServices(IServiceCollection services)
{
var connectionDict = new Dictionary<DatabaseConnectionName, string>
{
{ DatabaseConnectionName.Connection1, this.Configuration.GetConnectionString("dbConnection1") },
{ DatabaseConnectionName.Connection2, this.Configuration.GetConnectionString("dbConnection2") }
};
// Inject this dict
services.AddSingleton<IDictionary<DatabaseConnectionName, string>>(connectionDict);
// Inject the factory
services.AddTransient<IDbConnectionFactory, DapperDbConnectionFactory>();
// Register your regular repositories
services.AddScoped<IDiameterRepository, DiameterRepository>();
// ......
}
}
}
DiameterRepository.cs
using Dapper;
using System.Data;
namespace DL.SO.Project.Persistence.Dapper.Repositories
{
// Move the responsibility of picking the right connection string
// into an abstract base class so that I don't have to duplicate
// the right connection selection code in each repository.
public class DiameterRepository : DbConnection1RepositoryBase, IDiameterRepository
{
public DiameterRepository(IDbConnectionFactory dbConnectionFactory)
: base(dbConnectionFactory) { }
public IEnumerable<Diameter> GetAll()
{
const string sql = #"SELECT * FROM TABLE";
// No need to use using statement. Dapper will automatically
// open, close and dispose the connection for you.
return base.DbConnection.Query<Diameter>(sql);
}
// ......
}
}
DbConnection1RepositoryBase.cs
using System.Data;
using DL.SO.Project.Domain.Repositories;
namespace DL.SO.Project.Persistence.Dapper
{
public abstract class DbConnection1RepositoryBase
{
public IDbConnection DbConnection { get; private set; }
public DbConnection1RepositoryBase(IDbConnectionFactory dbConnectionFactory)
{
// Now it's the time to pick the right connection string!
// Enum is used. No magic string!
this.DbConnection = dbConnectionFactory.CreateDbConnection(DatabaseConnectionName.Connection1);
}
}
}
Then for other repositories that need to talk to the other connections, you can create a different repository base class for them.
using System.Data;
using DL.SO.Project.Domain.Repositories;
namespace DL.SO.Project.Persistence.Dapper
{
public abstract class DbConnection2RepositoryBase
{
public IDbConnection DbConnection { get; private set; }
public DbConnection2RepositoryBase(IDbConnectionFactory dbConnectionFactory)
{
this.DbConnection = dbConnectionFactory.CreateDbConnection(DatabaseConnectionName.Connection2);
}
}
}
using Dapper;
using System.Data;
namespace DL.SO.Project.Persistence.Dapper.Repositories
{
public class ParameterRepository : DbConnection2RepositoryBase, IParameterRepository
{
public ParameterRepository (IDbConnectionFactory dbConnectionFactory)
: base(dbConnectionFactory) { }
public IEnumerable<Parameter> GetAll()
{
const string sql = #"SELECT * FROM TABLE";
return base.DbConnection.Query<Parameter>(sql);
}
// ......
}
}
Hope all these help.
It was asked about 4 years ago... but anyway, maybe the answer will be useful to someone here:
I do it like this in all the projects.
First, I create a base class which contains a few helper methods like this:
public class BaseRepository
{
protected T QueryFirstOrDefault<T>(string sql, object parameters = null)
{
using (var connection = CreateConnection())
{
return connection.QueryFirstOrDefault<T>(sql, parameters);
}
}
protected List<T> Query<T>(string sql, object parameters = null)
{
using (var connection = CreateConnection())
{
return connection.Query<T>(sql, parameters).ToList();
}
}
protected int Execute(string sql, object parameters = null)
{
using (var connection = CreateConnection())
{
return connection.Execute(sql, parameters);
}
}
// Other Helpers...
private IDbConnection CreateConnection()
{
var connection = new SqlConnection(...);
// Properly initialize your connection here.
return connection;
}
}
And having such a base class I can easily create real repositories without any boilerplate code:
public class AccountsRepository : BaseRepository
{
public Account GetById(int id)
{
return QueryFirstOrDefault<Account>("SELECT * FROM Accounts WHERE Id = #Id", new { id });
}
public List<Account> GetAll()
{
return Query<Account>("SELECT * FROM Accounts ORDER BY Name");
}
// Other methods...
}
So all the code related to Dapper, SqlConnection-s and other database access stuff is located in one place (BaseRepository). All real repositories are clean and simple 1-line methods.
I hope it will help someone.
I created extension methods with a property that retrieves the connection string from configuration. This lets the callers not have to know anything about the connection, whether it's open or closed, etc. This method does limit you a bit since you're hiding some of the Dapper functionality, but in our fairly simple app it's worked fine for us, and if we needed more functionality from Dapper we could always add a new extension method that exposes it.
internal static string ConnectionString = new Configuration().ConnectionString;
internal static IEnumerable<T> Query<T>(string sql, object param = null)
{
using (SqlConnection conn = new SqlConnection(ConnectionString))
{
conn.Open();
return conn.Query<T>(sql, param);
}
}
internal static int Execute(string sql, object param = null)
{
using (SqlConnection conn = new SqlConnection(ConnectionString))
{
conn.Open();
return conn.Execute(sql, param);
}
}
I do it like this:
internal class Repository : IRepository {
private readonly Func<IDbConnection> _connectionFactory;
public Repository(Func<IDbConnection> connectionFactory)
{
_connectionFactory = connectionFactory;
}
public IWidget Get(string key) {
using(var conn = _connectionFactory())
{
return conn.Query<Widget>(
"select * from widgets with(nolock) where widgetkey=#WidgetKey", new { WidgetKey=key });
}
}
}
Then, wherever I wire-up my dependencies (ex: Global.asax.cs or Startup.cs), I do something like:
var connectionFactory = new Func<IDbConnection>(() => {
var conn = new SqlConnection(
ConfigurationManager.ConnectionStrings["connectionString-name"];
conn.Open();
return conn;
});
Best practice is a real loaded term. I like a DbDataContext style container like Dapper.Rainbow promotes. It allows you to couple the CommandTimeout, transaction and other helpers.
For example:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
using Dapper;
// to have a play, install Dapper.Rainbow from nuget
namespace TestDapper
{
class Program
{
// no decorations, base class, attributes, etc
class Product
{
public int Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public DateTime? LastPurchase { get; set; }
}
// container with all the tables
class MyDatabase : Database<MyDatabase>
{
public Table<Product> Products { get; set; }
}
static void Main(string[] args)
{
var cnn = new SqlConnection("Data Source=.;Initial Catalog=tempdb;Integrated Security=True");
cnn.Open();
var db = MyDatabase.Init(cnn, commandTimeout: 2);
try
{
db.Execute("waitfor delay '00:00:03'");
}
catch (Exception)
{
Console.WriteLine("yeah ... it timed out");
}
db.Execute("if object_id('Products') is not null drop table Products");
db.Execute(#"create table Products (
Id int identity(1,1) primary key,
Name varchar(20),
Description varchar(max),
LastPurchase datetime)");
int? productId = db.Products.Insert(new {Name="Hello", Description="Nothing" });
var product = db.Products.Get((int)productId);
product.Description = "untracked change";
// snapshotter tracks which fields change on the object
var s = Snapshotter.Start(product);
product.LastPurchase = DateTime.UtcNow;
product.Name += " World";
// run: update Products set LastPurchase = #utcNow, Name = #name where Id = #id
// note, this does not touch untracked columns
db.Products.Update(product.Id, s.Diff());
// reload
product = db.Products.Get(product.Id);
Console.WriteLine("id: {0} name: {1} desc: {2} last {3}", product.Id, product.Name, product.Description, product.LastPurchase);
// id: 1 name: Hello World desc: Nothing last 12/01/2012 5:49:34 AM
Console.WriteLine("deleted: {0}", db.Products.Delete(product.Id));
// deleted: True
Console.ReadKey();
}
}
}
Try this:
public class ConnectionProvider
{
DbConnection conn;
string connectionString;
DbProviderFactory factory;
// Constructor that retrieves the connectionString from the config file
public ConnectionProvider()
{
this.connectionString = ConfigurationManager.ConnectionStrings[0].ConnectionString.ToString();
factory = DbProviderFactories.GetFactory(ConfigurationManager.ConnectionStrings[0].ProviderName.ToString());
}
// Constructor that accepts the connectionString and Database ProviderName i.e SQL or Oracle
public ConnectionProvider(string connectionString, string connectionProviderName)
{
this.connectionString = connectionString;
factory = DbProviderFactories.GetFactory(connectionProviderName);
}
// Only inherited classes can call this.
public DbConnection GetOpenConnection()
{
conn = factory.CreateConnection();
conn.ConnectionString = this.connectionString;
conn.Open();
return conn;
}
}
Everyone appears to be opening their connections entirely too early? I had this same question, and after digging through the Source here - https://github.com/StackExchange/dapper-dot-net/blob/master/Dapper/SqlMapper.cs
You will find that every interaction with the database checks the connection to see if it is closed, and opens it as necessary. Due to this, we simply utilize using statements like above without the conn.open(). This way the connection is opened as close to the interaction as possible. If you notice, it also immediately closes the connection. This will also be quicker than it closing automatically during disposal.
One of the many examples of this from the repo above:
private static int ExecuteCommand(IDbConnection cnn, ref CommandDefinition command, Action<IDbCommand, object> paramReader)
{
IDbCommand cmd = null;
bool wasClosed = cnn.State == ConnectionState.Closed;
try
{
cmd = command.SetupCommand(cnn, paramReader);
if (wasClosed) cnn.Open();
int result = cmd.ExecuteNonQuery();
command.OnCompleted();
return result;
}
finally
{
if (wasClosed) cnn.Close();
cmd?.Dispose();
}
}
Below is a small example of how we use a Wrapper for Dapper called the DapperWrapper. This allows us to wrap all of the Dapper and Simple Crud methods to manage connections, provide security, logging, etc.
public class DapperWrapper : IDapperWrapper
{
public IEnumerable<T> Query<T>(string query, object param = null, IDbTransaction transaction = null, bool buffered = true, int? commandTimeout = null, CommandType? commandType = null)
{
using (var conn = Db.NewConnection())
{
var results = conn.Query<T>(query, param, transaction, buffered, commandTimeout, commandType);
// Do whatever you want with the results here
// Such as Security, Logging, Etc.
return results;
}
}
}
I wrap connection with the helper class:
public class ConnectionFactory
{
private readonly string _connectionName;
public ConnectionFactory(string connectionName)
{
_connectionName = connectionName;
}
public IDbConnection NewConnection() => new SqlConnection(_connectionName);
#region Connection Scopes
public TResult Scope<TResult>(Func<IDbConnection, TResult> func)
{
using (var connection = NewConnection())
{
connection.Open();
return func(connection);
}
}
public async Task<TResult> ScopeAsync<TResult>(Func<IDbConnection, Task<TResult>> funcAsync)
{
using (var connection = NewConnection())
{
connection.Open();
return await funcAsync(connection);
}
}
public void Scope(Action<IDbConnection> func)
{
using (var connection = NewConnection())
{
connection.Open();
func(connection);
}
}
public async Task ScopeAsync<TResult>(Func<IDbConnection, Task> funcAsync)
{
using (var connection = NewConnection())
{
connection.Open();
await funcAsync(connection);
}
}
#endregion Connection Scopes
}
Examples of usage:
public class PostsService
{
protected IConnectionFactory Connection;
// Initialization here ..
public async Task TestPosts_Async()
{
// Normal way..
var posts = Connection.Scope(cnn =>
{
var state = PostState.Active;
return cnn.Query<Post>("SELECT * FROM [Posts] WHERE [State] = #state;", new { state });
});
// Async way..
posts = await Connection.ScopeAsync(cnn =>
{
var state = PostState.Active;
return cnn.QueryAsync<Post>("SELECT * FROM [Posts] WHERE [State] = #state;", new { state });
});
}
}
So I don't have to explicitly open the connection every time.
Additionally, you can use it this way for the convenience' sake of the future refactoring:
var posts = Connection.Scope(cnn =>
{
var state = PostState.Active;
return cnn.Query<Post>($"SELECT * FROM [{TableName<Post>()}] WHERE [{nameof(Post.State)}] = #{nameof(state)};", new { state });
});
What is TableName<T>() can be found in this answer.
Hi #donaldhughes I'm new on it too, and I use to do this:
1 - Create a class to get my Connection String
2 - Call the connection string class in a Using
Look:
DapperConnection.cs
public class DapperConnection
{
public IDbConnection DapperCon {
get
{
return new SqlConnection(ConfigurationManager.ConnectionStrings["Default"].ToString());
}
}
}
DapperRepository.cs
public class DapperRepository : DapperConnection
{
public IEnumerable<TBMobileDetails> ListAllMobile()
{
using (IDbConnection con = DapperCon )
{
con.Open();
string query = "select * from Table";
return con.Query<TableEntity>(query);
}
}
}
And it works fine.