Question

我正在尝试创建一个SQL CLR示例，其中取决于processorClass，表示为字符串，我将能够返回处理请求的具体处理程序类型。当我添加这一行时：

MessageProcessorBase messageProcessor = MessageProcessorResolver.Create(MessageProcessorAssemblyName, processorClass);

导致以下错误：

消息6522，级别16，状态1，过程MessageProcessorTrigger，第1行在执行用户定义的例程或聚合“MessageProcessorTrigger”期间发生.NET Framework错误： System.IO.FileNotFoundException：无法加载文件或程序集“MyNamespace.MessageProcessor”或其依赖项之一。该系统找不到指定的文件。 System.IO.FileNotFoundException：找不到在System.Reflection.RuntimeAssembly._nLoad（AssemblyName fileName，String codeBase，Evidence assemblySecurity，RuntimeAssembly locationHint，StackCrawlMark＆amp; stackMark，IntPtr pPrivHostBinder，Boolean throwOnFileNotFound，Boolean forIntrospection，Boolean suppressSecurityChecks）在System.Reflection.RuntimeAssembly.nLoad（AssemblyName fileName，String codeBase，Evidence assemblySecurity，RuntimeAssembly locationHint，StackCrawlMark＆amp; stackMark，IntPtr pPrivHostBinder，Boolean throwOnFileNotFound，Boolean forIntrospection，Boolean suppressSecurityChecks）在System.Reflection.RuntimeAssembly.InternalLoadAssemblyName（AssemblyName assemblyRef，Evidence assemblySecurity，RuntimeAssembly reqAssembly，StackCrawlMark＆amp; stackMark，IntPtr pPrivHostBinder，Boolean throwOnFileNotFound，Boolean forIntrospection，Boolean suppressSecurityChecks）在System.Activator.CreateInstance（String assemblyString，String typeName，Boolean ignoreCase，BindingFlags bindingAttr，Binder binder，Object [] args，CultureInfo culture，Object [] activationAttributes，Evidence securityInfo，StackCrawlMark＆amp; stackMark）在System.Activator.CreateInstance（String assemblyName，String typeName） at MyNamespace.MessageProcessorFactory.Create（String assemblyName，String handler）在MyNamespace.Triggers.MessageProcessorTrigger（）

步骤

将数据插入表MessageQueue。
SQL CLR触发器调用Create方法来获取处理程序的实例（失败点）。
调用实例上的Handle方法。

表格

CREATE TABLE MessageProcessor.MessageQueue
(
    Id             INT IDENTITY(1,1) PRIMARY KEY NOT NULL
,   Name           NVARCHAR(50) NOT NULL
,   MessageType    INT  NOT NULL
,   StatusId       INT
,   ProcessorClass NVARCHAR(50)
)

ALTER DATABASE MYBD SET TRUSTWORTHY ON;
GO

exec sp_configure 'clr enabled', 1
GO

reconfigure
GO

触发器（SQL CLR）

public partial class Triggers
{
    private const string MessageProcessorAssemblyName = "MyProcessor.MessageProcessor";
    // Enter existing table or view for the target and uncomment the attribute line
    //[SqlTrigger(Name = "MessageProcessorTrigger", Target = "MessageProcessor.MessageQueue", Event = "FOR INSERT")]
    public static void MessageProcessorTrigger()
    {
        SqlTriggerContext triggerContext = SqlContext.TriggerContext;
        string processorClass = string.Empty;

        if (triggerContext == null) return;
        if (triggerContext.TriggerAction == TriggerAction.Insert)
        {
            using (SqlConnection conn = new SqlConnection(" context connection=true"))
            {
                conn.Open();
                SqlCommand command = conn.CreateCommand();
                SqlPipe sqlP = SqlContext.Pipe;

                command.Connection = conn;
                command.CommandText = "SELECT ProcessorClass FROM INSERTED";

                processorClass = command.ExecuteScalar().ToString();
                sqlP.Send(string.Format("Called MessageProcessor {0}", processorClass));

                //var handle = Activator.CreateInstance(MessageProcessorAssemblyName, processorClass);

                MessageProcessorBase messageProcessor = MessageProcessorFactory.Create(MessageProcessorAssemblyName,
                    processorClass);
                messageProcessor.HandleMessage(string.Empty);
            }
        }
    }
}

最后调用Resolver来获取调用Handle Method的实例。

public class MessageProcessorResolver
{
    public static MessageProcessorBase Create(string assemblyName, string handler)
    {
        return (MessageProcessorBase)Activator.CreateInstance(assemblyName, handler).Unwrap();
    }
}

我使用Permission Set UNSAFE创建程序集，只是为了启用事件记录，因为这是当前处理程序执行的唯一操作。
它似乎是调用Activator.CreateInstance的问题，因为当我在Create方法中将返回类型设置为CustomerMessageHandler时，一切都按预期工作。我知道在SQLCLR中不允许使用Reflection，并且错误似乎指向了这个方向，但我已经看到了这个使用here的例子，这让我想到也许我只是遗漏了一些东西。

为了完整性，MessageProcessorBase只是一个抽象类，只有一个方法，Handle

public abstract class MessageProcessorBase
{
    public virtual void HandleMessage(string messageDetails)
    {
        Console.WriteLine("Handled by Message Processor Base Method");
    }
}

，而CustomerMessageHandler只是：

public class CustomerMessageHandler : MessageProcessorBase
{
    public override void HandleMessage(string messageDetails)
    {
        const string source = "Message Processor SQLCLR";
        const string log = "Application";
        const string logEvent = "Customer Processor";

        if (!EventLog.SourceExists(source))
            EventLog.CreateEventSource(source, log);

        EventLog.WriteEntry(source, logEvent);
        Console.WriteLine("Handled by Customer Handler");
    }
}

请原谅这篇文章的篇幅，我尽量做到尽可能完整。

从SQLCLR调用Activator.CreateInstance会导致异常

0 个答案: