A programmer day with “That assembly does not allow partially trusted callers”

I make a website, works on local IIS. Performs user registration  + uploading some zip files + generating custom feeds for those zip files.

Using SharpZipLib_0860_Bin ( to unzip file ) , StringTemplate.dll ( to perform custom feed generation ) and NUnit-2.5.7.10213 ( to perform tests).

So far ,so good. Moving into production . User registration works, upload works, trying feeds

“That assembly does not allow partially trusted callers”
Feeds were generated with StringTemplate- it was custom feeds ;-).

Searching , talking with hosting – seeing that this happens if your asp.net does not run under full trust , but under “Medium trust”.

Normally the provider does not want to change and send me advice to put AllowPartiallyTrustedCallersAttribute (APTCA) on the class:
http://msdn.microsoft.com/en-us/library/system.security.allowpartiallytrustedcallersattribute.aspx

This does not work without signing with a strong name – so I generate the snk file , sign mine assemblies, re-deploy. Same error:

“That assembly does not allow partially trusted callers”

That is normally and I have suspected – because I have to sign the stringtemplate, not mine dll.

Trying to see if the stringtemplate is signed  -it is! When put AllowPartiallyTrustedCallersAttribute  and trying to re-build – failed because I do not have his snk

Then, in disperation, I remove the snk from stringtemplate and re-make my project.

And now –

System.Security.SecurityException: Request failed.

Antlr.StringTemplate.FileSystemTemplateLoader.InternalLoadTemplateContents(String templateName) +0

That means that the files to read contents to generate feeds are not accesible to read. But, oh my dear .NET framework :could you not tell from the beginning ?

So, possible solutions to identify causes :  identify the assembly that  causes the harm and either

1. put a snk to this assembly and for all assemblies in superior chaining

2. remove the snk from this assembly

In either case, you should see what the error is.
So how I managed to solve ?
1. Put Reflector and dissasemble the source.
2. Re-compile without snk.
3. Put in Web.Config 4. Compile and run with debug
Now it stops at :
string templateText = InternalLoadTemplateContents(templateName);

This , in StringTemplate class, was 

  protected override string InternalLoadTemplateContents(string templateName)
        {
            string templateText = null;
            string templateLocation = null;

            try
            {
                //templateLocation = Path.Combine(LocationRoot, GetLocationFromTemplateName(templateName));
                templateLocation = string.Format("{0}/{1}", LocationRoot, GetLocationFromTemplateName(templateName)).Replace('\\', '/');
                StreamReader br;
                try
                {
                    br = new StreamReader(templateLocation, encoding);
                }
                catch(FileNotFoundException)
                {
                    return null;
                }
                catch(DirectoryNotFoundException)
                {
                    return null;
                }
                catch(Exception ex)
                {
                    throw new TemplateLoadException("Cannot open template file: " + templateLocation, ex);
                }

                try 
                {
                    templateText = br.ReadToEnd();
                    if ((templateText != null) && (templateText.Length > 0))
                    {
                        //templateText = templateText.Trim();

                        if (filesWatcher == null)
                        {
                            filesWatcher = new FileSystemWatcher(LocationRoot, "*.st");
                            //filesWatcher.InternalBufferSize *= 2;
                            filesWatcher.NotifyFilter = 
                                NotifyFilters.LastWrite 
                                | NotifyFilters.Attributes
                                | NotifyFilters.Security 
                                | NotifyFilters.Size 
                                | NotifyFilters.CreationTime 
                                | NotifyFilters.DirectoryName 
                                | NotifyFilters.FileName;
                            filesWatcher.IncludeSubdirectories = true;
                            filesWatcher.Changed += new FileSystemEventHandler(OnChanged);
                            filesWatcher.Deleted += new FileSystemEventHandler(OnChanged);
                            filesWatcher.Created += new FileSystemEventHandler(OnChanged);
                            filesWatcher.Renamed += new RenamedEventHandler(OnRenamed);
                            filesWatcher.EnableRaisingEvents = true;
                        }
                    }
                    fileSet.Remove(templateLocation);
                }
                finally
                {
                    if (br != null) ((IDisposable)br).Dispose();
                    br = null;
                }
            }
            catch (ArgumentException ex) 
            {
                string message;
                if (templateText == null)
                    message = string.Format("Invalid file character encoding: {0}", encoding);
                else
                    message = string.Format("The location root '{0}' and/or the template name '{1}' is invalid.", LocationRoot, templateName);

                throw new TemplateLoadException(message, ex);
            }
            catch (IOException ex) 
            {
                throw new TemplateLoadException("Cannot close template file: " + templateLocation, ex);
            }
            return templateText;
        }

Does something ring a bell to you ?
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Yes – FileSystemWatcher .
http://msdn.microsoft.com/en-us/library/system.io.filesystemwatcher.aspx
[IODescriptionAttribute(“FileSystemWatcherDesc”)]
[PermissionSetAttribute(SecurityAction.LinkDemand, Name = “FullTrust”)]
[PermissionSetAttribute(SecurityAction.InheritanceDemand, Name = “FullTrust”)]
public class FileSystemWatcher : Component,

Solution : Once defined my FileSystemTemplateLoader_MT – without FileSystemWatcher – all works well
So – the idea is : reflector, sources, find something strange. Remove, rebuild, re-test
(Thanks to OrcsWeb team for helping me on this problem !)