没有配置文件的实体框架跟踪提供程序包装

Question

我想使用实体框架代码与SQLCE4数据库的第一种方法。一切似乎都很好，但我有问题调试sql查询。我发现EFTracing从http://efwrappers.codeplex.com/应该是我所需要的，但我不知道如何使用它没有app.config文件。我不太喜欢这种配置。我只想使用c#代码来设置和运行一切。我认为应该使用这样的代码:

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;
    }
}

但是它不起作用。它抛出异常:

无法确定类型连接的提供程序名称EFTracingProvider.EFTracingConnection"。

是否有任何简单的方法如何正确地创建包装连接仅在代码中?

Answer 1

解决我的问题是以下DbContext对象。

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;
  }
}

所以现在我可以使用上下文和连接自动创建包装或未包装的SqlCe取决于TraceEnabled属性。

using (var context = new MyContext())
{
    var a = context.Projects.FirstOrDefault();
}

Answer 2

跟踪SQL查询的真正方法是像这样调用ToString方法:

var t = from c in _entities.CompanyDetail
        select c;
string test = t.ToString();

我不知道EFTracing，但是你可能想尝试MVCMiniProfiler。尽管名称MVCMiniProfiler也提供SQL查询分析和工作没有配置文件。

Answer 3

我通过在ObjectContext周围创建包装器类并使用该包装器而不是原始上下文来实现这一点。下面是一个示例上下文包装器:

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; }
    }
}

我还有一个定义跟踪输出方法的静态类，并有一个初始化跟踪的静态方法。:

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是我正在使用的日志接口。你需要替换你自己的接口/方法。

InitSqlTracing方法在我的程序启动时被调用一次，然后LoggedContext类被用来记录实体框架生成的所有SQL。

将它们与示例代码放在一起:

EFTracingExtensions.InitSqlTracing(logger);    // only call this once
using (var context = new LoggedContext())
{
    var a = from data in context.Projects select data;
}