使用RazorEngine同时解析Razor模板

Question

我在MVC 3 Web应用程序中使用RazorEngine库(http://razorengine.codeplex.com/)来使用Razor模板语言来解析字符串(不是视图).

一般来说,这很好.但是,当多个用户访问同时解析Razor模板的代码时,我偶尔会看到内部Razor编译器中出现的错误(请参阅下面的两个).我在解释这些错误时遇到了麻烦,但我的猜测是我调用Razor编译器的方式不是并发安全的.

这是Razor编译器的已知问题吗？正常的Razor视图(.cshtml)如何不遇到这个问题？有没有一种解决方法比将所有应用程序的调用包含在互斥锁中的Razor.Parse更好？

我的调用代码如下,只是一个简单的包装Razor.Parse:

    protected string ParseTemplate<T>(string templateString, T model)
    {
        //This binderAssembly line is required by NUnit to prevent template compilation errors
        var binderAssembly = typeof(Microsoft.CSharp.RuntimeBinder.Binder).Assembly;
        var result = Razor.Parse(templateString, model);
        return result;
    }

错误一:

System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: chunkLength
at System.Text.StringBuilder.ToString()
at System.Web.Razor.Generator.RazorCodeGenerator.BlockContext.MarkEndGeneratedCode()
at System.Web.Razor.Generator.RazorCodeGenerator.WriteBlock(BlockContext block)
at System.Web.Razor.Parser.ParserContext.FlushNextOutputSpan()
at System.Web.Razor.Parser.ParserContext.StartBlock(BlockType blockType, Boolean outputCurrentBufferAsTransition)
at System.Web.Razor.Parser.ParserBase.ParseComment()
at System.Web.Razor.Parser.ParserBase.TryParseComment(SpanFactory previousSpanFactory)
at System.Web.Razor.Parser.ParserBase.ParseBlockWithOtherParser(SpanFactory previousSpanFactory, Boolean collectTransitionToken)
at System.Web.Razor.Parser.HtmlMarkupParser.TryStartCodeParser(Boolean isSingleLineMarkup, Boolean documentLevel)
at System.Web.Razor.Parser.HtmlMarkupParser.ParseRootBlock(Tuple`2 nestingSequences, Boolean caseSensitive)
at System.Web.Razor.Parser.RazorParser.Parse(LookaheadTextReader input, ParserVisitor visitor)
at System.Web.Razor.RazorTemplateEngine.GenerateCodeCore(LookaheadTextReader input, String className, String rootNamespace, String sourceFileName, Nullable`1 cancelToken)
at System.Web.Razor.RazorTemplateEngine.GenerateCode(TextReader input, String className, String rootNamespace, String sourceFileName, Nullable`1 cancelToken)
at System.Web.Razor.RazorTemplateEngine.GenerateCode(TextReader input)
at RazorEngine.Compilation.CompilerServiceBase.GetCodeCompileUnit(String className, String template, ISet`1 namespaceImports, Type templateType, Type modelType)
at RazorEngine.Compilation.DirectCompilerServiceBase.Compile(TypeContext context)
at RazorEngine.Compilation.DirectCompilerServiceBase.CompileType(TypeContext context)
at RazorEngine.Templating.TemplateService.CreateTemplate(String template, Type modelType)
at RazorEngine.Templating.TemplateService.Parse[T](String template, T model, String name)
at RazorEngine.Razor.Parse[T](String template, T model, String name)

错误二:

System.ObjectDisposedException: Cannot read from a closed TextReader.
at System.IO.StringReader.Read()
at System.Web.Razor.Text.BufferingTextReader.NextCharacter()
at System.Web.Razor.Text.BufferingTextReader.Read()
at System.Web.Razor.Parser.ParserContext.AcceptCurrent()
at System.Web.Razor.Parser.HtmlMarkupParser.ParseRootBlock(Tuple`2 nestingSequences, Boolean caseSensitive)
at System.Web.Razor.Parser.RazorParser.Parse(LookaheadTextReader input, ParserVisitor visitor)
at System.Web.Razor.RazorTemplateEngine.GenerateCodeCore(LookaheadTextReader input, String className, String rootNamespace, String sourceFileName, Nullable`1 cancelToken)
at System.Web.Razor.RazorTemplateEngine.GenerateCode(TextReader input, String className, String rootNamespace, String sourceFileName, Nullable`1 cancelToken)
at System.Web.Razor.RazorTemplateEngine.GenerateCode(TextReader input)
at RazorEngine.Compilation.CompilerServiceBase.GetCodeCompileUnit(String className, String template, ISet`1 namespaceImports, Type templateType, Type modelType)
at RazorEngine.Compilation.DirectCompilerServiceBase.Compile(TypeContext context)
at RazorEngine.Compilation.DirectCompilerServiceBase.CompileType(TypeContext context)
at RazorEngine.Templating.TemplateService.CreateTemplate(String template, Type modelType)
at RazorEngine.Templating.TemplateService.Parse[T](String template, T model, String name)
at RazorEngine.Razor.Parse[T](String template, T model, String name)

Answer 1

更新: 根据他们团队的博客文章,最新版本3.x(在Github上)现在是线程安全的.我没有审查其线程安全性的真实性,但假设它已经正确实现.请考虑此答案的其余部分仅用于历史目的.

从代码来看,这个项目看起来并不是远程线程安全的.

Razor.Parse:

public static string Parse<T>(string template, T model, string name = null)
{
    return DefaultTemplateService.Parse<T>(template, model, name);
}

TemplateService.Parse:

public string Parse<T>(string template, T model, string name = null)
{
    var instance = GetTemplate(template, typeof(T), name);
    ...
}

TemplateService.GetTemplate:

internal ITemplate GetTemplate(string template, Type modelType, string name)
{
    if (!string.IsNullOrEmpty(name))
        if (templateCache.ContainsKey(name))
            return templateCache[name];

    var instance = CreateTemplate(template, modelType);

    if (!string.IsNullOrEmpty(name))
        if (!templateCache.ContainsKey(name))
            templateCache.Add(name, instance);

    return instance;
}

所以,Razor.Parse是一种静态方法. DefaultTemplateService是一个静态属性Razor,并Parse和GetTemplate实例方法,但静态有效调用静态的,因为DefaultTemplateService.这意味着所有线程都经过相同的实例并通过GetTemplate.你会注意到,在不获取任何锁的情况下GetTemplate改变state(templateCache).因此,此代码不是线程安全的.