I'm a beginner with C# MVC (about 6 months of self-learning), currently working on my first project, and I recently came across the problem of an SQL dependency duplicating when the user refreshes a page.
Through looking at various posts and articles across sites, I have cobbled together a working implementation, but I'm still getting my head around some of the elements of it, especially the singleton design pattern and the various class and property modifiers.
I would like to know, are there any gaping holes in my code, or any other considerations I should be making as I plan to set up a few more dependencies?
To give a bit of background to the project scale, it will be used by up to 500 users at a time, and the data affecting the dependency will change up to around once a second during busy periods.
Many thanks in advance. :)
Here is my dependency class:
public sealed class UMCSingleton
{
private static UMCSingleton instance;
private static string connString = ConfigurationManager.ConnectionStrings["ServerConnection"].ConnectionString;
private static SqlConnection conn = new SqlConnection(connString);
private SqlDependency dependency;
private static volatile object padlock = new object();
private UMCSingleton() {}
public static UMCSingleton Instance
{
get
{
if (instance == null)
{
lock (padlock)
{
if (instance == null)
{
instance = new UMCSingleton();
}
}
}
return instance;
}
}
public static SqlConnection getUMCConnection()
{
try
{
if(conn == null)
{
conn = new SqlConnection(connString);
conn.Open();
return conn;
}
if(conn.State == ConnectionState.Closed)
{
conn.ConnectionString = connString;
conn.Open();
}
}
catch (SqlException e) {}
finally {}
return conn;
}
public void RegisterUnmanagdCallDependency()
{
using (getUMCConnection())
{
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandType = CommandType.Text;
cmd.CommandText = "SELECT [CallRef], [CallLoggedByUserId] FROM [dbo].[UnplannedCustomers] Where [ServiceFlowId] = 1";
cmd.Notification = null;
if (dependency == null || dependency.HasChanges == true)
{
dependency = new SqlDependency(cmd);
dependency.OnChange += new OnChangeEventHandler(dependency_OnChange);
}
using (SqlDataReader reader = cmd.ExecuteReader()) {}
}
}
}
void dependency_OnChange(object sender, SqlNotificationEventArgs e) //this will be called when any changes occur in db table.
{
if (e.Type == SqlNotificationType.Change)
{
SqlDependency dependency = (SqlDependency)sender;
if (dependency.HasChanges == true)
{
dependency.OnChange -= dependency_OnChange;
}
UnmanagedCallHub.ShowCalls();
RegisterUnmanagdCallDependency();
}
}
}
Here is my hub class:
public class UnmanagedCallHubData
{
public string CallRef { get; set; }
public string RaisedBy { get; set; }
}
public class UnmanagedCallHub : Hub
{
private ApplicationDbContext _context;
public UnmanagedCallHub()
{
_context = new ApplicationDbContext();
}
public static void ShowCalls()
{
IHubContext context = GlobalHost.ConnectionManager.GetHubContext<UnmanagedCallHub>();
context.Clients.All.UpdateCalls();
}
}
And finally my api controller:
public class UnmanagedCallController : ApiController
{
private ApplicationDbContext _context;
private UserProfile _uPro;
//CONSTRUCTOR SETS DB CONTEXT
public UnmanagedCallController()
{
_context = new ApplicationDbContext();
ApplicationUser user = HttpContext.Current.GetOwinContext()
.GetUserManager<ApplicationUserManager>().FindById(HttpContext.Current.User.Identity.GetUserId());
_uPro = _context.UserProfiles.SingleOrDefault(x => x.UserId == user.Id);
}
[HttpGet]
[Authorize]
public List<UnmanagedCallHubData> GetUnmanagedCalls()
{
List<UnmanagedCallHubData> calls = _context.UnplannedCustomers
.Where(x => x.ServiceFlowId == 1)
.Where(x => x.CurrentManagerUserId == null)
.Select(x => new UnmanagedCallHubData
{
CallRef = x.CallRef,
RaisedBy = x.CallLoggedByUserId
}).ToList();
UMCSingleton.Instance.RegisterUnmanagdCallDependency();
return calls;
}
}
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))
{
...
}
}
My services take a DbContext in their constructor, and I have created a UnitOfWork class that contains all my services in order to make sure the same DbContext is used between them all.
Sample of unitofwork class
private myEntities myContext
public UnitOfWork()
{
myContext = new myEntities();
}
private RequestService requestService;
public RequestService RequestService
{
get
{
if (requestService == null)
requestService = new RequestService(myContext);
return requestService;
}
}
By Using this unitofwork class all the DbContext for my services are now consistent and a change made in one service will appear in another.
However if i need to change the actual Entity context class then that does not get persisted across each service.
Below i have a "Refresh" method that re-initializes it (I need to refresh the context so i can have this class work with some legacy code).
public void Refresh()
{
myContext = new myEntities();
}
However my service classes DbContext objects aren't passed by ref so the context is not set to a new instance of my entity class and this results in the context not being refreshed.
So I think i can solve this by passing by ref as shown below
Service class sample
MyEntities myContext;
public RequestService(ref MyEntities myContext)
{
this.myContext = myContext;
}
However i have seen people say you should not pass context classes by ref so i am curious if there is a better way out there and i am looking at this the wrong way?
Edit
Sorry turns out my proposed solution of passing by ref does not solve my problem, but i am still interested as to how i can update the entity context on the UnitOfWork class e.g. setting it to null and have that effect the service classes.
Never ever should you share DbContext, by reference or as reference. It is not thread safe.
http://msdn.microsoft.com/en-us/data/jj729737.aspx
If you need an easy way to generate multiple DbContext, use ObjectPool from Parallel Extensions Extras.
Update 1
#tia is correct in saying that the private instance will not be updated when original changes:
class Program
{
static void Main(string[] args)
{
var pool1 = new ObjectPool<IDbConnection>(() => new SqlConnection("Data Source=server1"));
var service = new Service(ref pool1);
pool1 = new ObjectPool<IDbConnection>(() => new SqlConnection("Data Source=server2"));
Console.WriteLine(service.Pool.GetObject().ConnectionString);
}
}
class Service
{
private ObjectPool<IDbConnection> connectionPool;
public Service(ref ObjectPool<IDbConnection> pool) { this.connectionPool = pool; }
public ObjectPool<IDbConnection> Pool { get { return connectionPool; } }
}
Will print "Data Source=server 1", even if it would be a static field.
Enter Monostate, a wicked pattern, very similar to Singleton.
class Program
{
static void Main(string[] args)
{
var mop = new MonoObjectPool();
mop.Pool = new ObjectPool<IDbConnection>(() => new SqlConnection("Data Source=server1"));
var service = new Service();
mop.Pool = new ObjectPool<IDbConnection>(() => new SqlConnection("Data Source=server2"));
Console.WriteLine(service.Pool.GetObject().ConnectionString);
}
}
internal class MonoObjectPool
{
private static ObjectPool<IDbConnection> pool1;
public ObjectPool<IDbConnection> Pool
{
get { return pool1; }
set { pool1 = value; }
}
}
class Service
{
public ObjectPool<IDbConnection> Pool { get { return new MonoObjectPool().Pool; } }
}
I am getting rid of the constructor for service, as I can always get the current IDbConnection generator. There will always be only one instance of it, regardless how many times someone instantiates the MonoObjectPool.
Update 2
The other option might be to use Autofac, but I am not too familiar with it, yet, so I can't give you an example how a type could get resolved in a service instance. Here is a simple example:
class Program
{
private static IContainer container { get; set; }
static void Main(string[] args)
{
var builder = new ContainerBuilder();
builder.RegisterType<DbCtx1>().As<IDbCtx>();
container = builder.Build();
using (var scope = container.BeginLifetimeScope())
{
var dbctx = scope.Resolve<IDbCtx>();
Console.WriteLine(dbctx.GetType());
}
builder = new ContainerBuilder();
builder.RegisterType<DbCtx2>().As<IDbCtx>();
container = builder.Build();
using (var scope = container.BeginLifetimeScope())
{
var dbctx = scope.Resolve<IDbCtx>();
Console.WriteLine(dbctx.GetType());
}
}
}
interface IDbCtx
{
}
class DbCtx1 : IDbCtx { }
class DbCtx2 : IDbCtx { }
Update 3
So going back to the Monostate, this works as expected:
class Program
{
static void Main(string[] args)
{
var mop = new MonoObjectPool();
mop.Pool = new ObjectPool<IDbConnection>(() => new SqlConnection("Data Source=server1"));
var service = new Service(mop);
mop.Pool = new ObjectPool<IDbConnection>(() => new SqlConnection("Data Source=server2"));
Console.WriteLine(service.Pool.GetObject().ConnectionString);
}
}
internal class MonoObjectPool
{
private static ObjectPool<IDbConnection> pool1;
public ObjectPool<IDbConnection> Pool
{
get { return pool1; }
set { pool1 = value; }
}
}
class Service
{
private MonoObjectPool myPool;
public Service(MonoObjectPool pool) { myPool = pool; }
public ObjectPool<IDbConnection> Pool { get { return myPool.Pool; } }
}
I hope this helps.
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.
I would like to use Entity Framework Code first approach with SQLCE4 database. Everything seems to be really nice but I have problem with debugging sql queries. I found that EFTracing from http://efwrappers.codeplex.com/ should be exactly what I need but I don't know how to use it without app.config file. I am not big fan of this configuration. I want to use only C# code to set everything up and running. I think it should be fine to use code like this:
using (System.Data.Common.DbConnection c =
new EFTracingProvider.EFTracingConnection(
new System.Data.SqlServerCe.SqlCeConnection(conn)))
{
using (var context = new MyContext(c))
{
var a = from data in context.Projects select data;
}
}
But it doesn't work. It throws exception:
Unable to determine the provider name for connection of type
EFTracingProvider.EFTracingConnection'.
Is there any simple way how to correctly create wrapped connection only in code?
Solution for my problem is following DbContext object.
public class MyContext : DbContext
{
public MyContext()
: base(CreateConnection("Data Source=file.sdf",
"System.Data.SqlServerCe.4.0"), true)
{ }
public DbSet<Project> Projects { get; set; }
public static bool TraceEnabled = true;
private static DbConnection CreateConnection(string connectionString,
string providerInvariantName)
{
DbConnection connection = null;
if (TraceEnabled)
{
EFTracingProviderConfiguration.RegisterProvider();
EFTracingProviderConfiguration.LogToConsole = true;
string wrapperConnectionString = String.Format(#"wrappedProvider={0};{1}",
providerInvariantName, connectionString);
connection = new EFTracingConnection()
{
ConnectionString = wrapperConnectionString
};
}
else
{
DbProviderFactory factory = DbProviderFactories.GetFactory(providerInvariantName);
connection = factory.CreateConnection();
connection.ConnectionString = connectionString;
}
return connection;
}
}
So now I can use just context and connection is created automatically for wrapped or unwrapped SqlCe depending on TraceEnabled property.
using (var context = new MyContext())
{
var a = context.Projects.FirstOrDefault();
}
The genuine way to trace SQL queries is to call the ToString method like that :
var t = from c in _entities.CompanyDetail
select c;
string test = t.ToString();
I don't know EFTracing, but you might want to try MVCMiniProfiler. Despite the name MVCMiniProfiler also provide SQL queries profiling and work without config file.
I've done this by creating a wrapper class around the ObjectContext and using that wrapper instead of the original context. Here's an example context wrapper:
public partial class LoggedContext : MyContext
{
public LoggedContext()
: this("name=MyEntities") // Adjust this to match your entities
{
}
public LoggedContext(string connectionString)
: base(EntityConnectionWrapperUtils.CreateEntityConnectionWithWrappers(connectionString)
{
}
private EFTracingConnection TracingConnection
{
get { return this.UnwrapConnection<EFTracingConnection>(); }
}
public event EventHandler<CommandExecutionEventArgs> CommandExecuting
{
add { this.TracingConnection.CommandExecuting += value; }
remove { this.TracingConnection.CommandExecuting -= value; }
}
public event EventHandler<CommandExecutionEventArgs> CommandFinished
{
add { this.TracingConnection.CommandFinished += value; }
remove { this.TracingConnection.CommandFinished -= value; }
}
public event EventHandler<CommandExecutionEventArgs> CommandFailed
{
add { this.TracingConnection.CommandFailed += value; }
remove { this.TracingConnection.CommandFailed -= value; }
}
}
I also have a static class that defines the tracing output method and has a static method to initialize tracing. Here:
public static class EFTracingExtensions
{
private static ILogger _logger;
public static void InitSqlTracing(ILogger logger)
{
_logger = logger;
EFTracingProviderConfiguration.RegisterProvider();
if (logger.IsLoggingEnabled()) // Don't add logging hooks if logging isn't enabled
{
EFTracingProviderConfiguration.LogAction = new Action<CommandExecutionEventArgs>(AppendSqlLog);
}
}
private static void AppendSqlLog(CommandExecutionEventArgs e)
{
if (e.Status != CommandExecutionStatus.Executing) // we only care about Finished and Failed
{
StringBuilder msg = new StringBuilder(e.ToTraceString().TrimEnd());
msg.Append(Environment.NewLine);
if (e.Result is SqlDataReader)
{
int rows = ((SqlDataReader)e.Result).HasRows ? ((SqlDataReader)e.Result).RecordsAffected : 0;
msg.AppendFormat("*** {0} rows affected", rows);
}
else if (e.Result is int)
{
msg.AppendFormat("*** result: {0}", e.Result);
}
else
{
msg.AppendFormat("*** finished, result: {0}", e.Result);
}
msg.Append(Environment.NewLine);
msg.AppendFormat(" [{0}] [{1}] in {2} seconds", e.Method, e.Status, e.Duration);
_logger.Log(msg.ToString(), LoggerCategories.SQL);
}
}
}
ILogger is the logging interface I'm using. You need to substitute your own interface/methods.
The InitSqlTracing method is invoked once when my program starts up, and then the LoggedContext class is used to log all the SQL generated by Entity Framework.
Putting it all together with your sample code:
EFTracingExtensions.InitSqlTracing(logger); // only call this once
using (var context = new LoggedContext())
{
var a = from data in context.Projects select data;
}