c# - 带有 c# 表达式的 XAMLX 工作流

Question

我正在 vs2012/.Net 4.5/WF 4.5 中开发自托管工作流，并且很难弄清楚以下消息

Expression Activity type 'CSharpValue`1' requires compilation in order to run. Please ensure that the workflow has been compiled.

当我调用由服务引用生成的事件时会发生此错误(当您添加 WCF 服务引用时，端点上的每个操作都会成为一个事件)。

在 MSDN 中环顾四周，我发现了这些文章:

• http://msdn.microsoft.com/en-us/library/ee358749.aspx
• http://msdn.microsoft.com/en-us/library/29110be7-f4e3-407e-8dbe-78102eb21115#CodeWorkflows

他们说

When a workflow service is hosted in IIS or WAS then no additional steps are required, but if the XAML workflow service is self-hosted, then the C# expressions must be compiled

所以，我终于回答了我的问题:我应该怎么做才能按 F5 键并调试我的工作流，让它在 IIS 上运行？并停止这个该死的异常......

我尝试转到项目配置并设置为使用本地 IIS，如下所示:

但由于我仍然收到错误，我认为它无法正常工作...

Answer 1

老问题，但在将各种信息拼凑了一天之后，我想我应该分享一下，以防其他人遇到这个问题。

来自 C# 表达式 MSDN 文档:

XAMLX 工作流服务支持 C# 表达式。 如果工作流服务托管在 IIS 或 WAS 中，则不需要额外的步骤，但如果 XAML 工作流服务是自托管的，则必须编译 C# 表达式。

在您添加自定义 WorkflowHostFactory 之前，这是真的。在这种情况下，如果您覆盖了错误的方法，您的 C# 将不会被编译。以下代码不会编译 C# 表达式，您将得到可怕的结果:

Expression Activity type 'CSharpValue`1' requires compilation in order to run. Please ensure that the workflow has been compiled.

或者，如果您不查看跟踪消息，则更有帮助:

System.ServiceModel.FaultException: The operation could not be performed because WorkflowInstance '5cfc33d1-b546-4ba8-a8ec-86d3cb16a68b' was aborted.

   public override ServiceHostBase CreateServiceHost(string constructorString, Uri[] baseAddresses)
    {
        return base.CreateServiceHost(constructorString, baseAddresses);
    }

您可以通过覆盖其他工厂方法然后使用 MSDN C# Expressions in Workflow Foundation 4.5 提供的代码编译您的事件来解决此问题:

 protected override WorkflowServiceHost CreateWorkflowServiceHost(WorkflowService service, Uri[] baseAddresses)
    {
        CompileExpressions(service.Body);
        return base.CreateWorkflowServiceHost(service, baseAddresses);
    }

这是整个 WorkflowServiceHostFactory:

 public class MyWorkflowServiceHostFactory : WorkflowServiceHostFactory
{
    protected override WorkflowServiceHost CreateWorkflowServiceHost(WorkflowService service, Uri[] baseAddresses)
    {
        CompileExpressions(service.Body);
        return base.CreateWorkflowServiceHost(service, baseAddresses);
    }

    static void CompileExpressions(Activity activity)
    {
        // activityName is the Namespace.Type of the activity that contains the
        // C# expressions.
        string activityName = activity.GetType().ToString();

        // Split activityName into Namespace and Type.Append _CompiledExpressionRoot to the type name
        // to represent the new type that represents the compiled expressions.
        // Take everything after the last . for the type name.
        string activityType = activityName.Split('.').Last() + "_CompiledExpressionRoot";
        // Take everything before the last . for the namespace.
        string activityNamespace = string.Join(".", activityName.Split('.').Reverse().Skip(1).Reverse());

        // Create a TextExpressionCompilerSettings.
        TextExpressionCompilerSettings settings = new TextExpressionCompilerSettings
        {
            Activity = activity,
            Language = "C#",
            ActivityName = activityType,
            ActivityNamespace = activityNamespace,
            RootNamespace = null,
            GenerateAsPartialClass = false,
            AlwaysGenerateSource = true,
            ForImplementation = false
        };

        // Compile the C# expression.
        TextExpressionCompilerResults results =
            new TextExpressionCompiler(settings).Compile();

        // Any compilation errors are contained in the CompilerMessages.
        if (results.HasErrors)
        {
            throw new Exception("Compilation failed.");
        }

        // Create an instance of the new compiled expression type.
        ICompiledExpressionRoot compiledExpressionRoot =
            Activator.CreateInstance(results.ResultType,
                new object[] { activity }) as ICompiledExpressionRoot;

        // Attach it to the activity.
        CompiledExpressionInvoker.SetCompiledExpressionRoot(
            activity, compiledExpressionRoot);
    }       
}