XmlSerializer giving FileNotFoundException at constructor

Question

An application I ve been working with is failing when I try to serialize types   A statement like  XmlSerializer lizer   new XmlSerializer typeof MyType      produces   System IO FileNotFoundException occurred   Message  Could not load file or assembly   Containing Assembly of MyType  XmlSerializers  Version 1 0 0 0  Culture neutral  PublicKeyToken null  or one of its dependencies  The system cannot find the file specified     Source  mscorlib    FileName   Containing Assembly of MyType  XmlSerializers  Version 1 0 0 0  Culture neutral  PublicKeyToken null    FusionLog      StackTrace         at System Reflection Assembly  nLoad AssemblyName fileName  String codeBase  Evidence assemblySecurity  Assembly locationHint  StackCrawlMark amp  stackMark  Boolean throwOnFileNotFound  Boolean forIntrospection         at System Reflection Assembly nLoad AssemblyName fileName  String codeBase  Evidence assemblySecurity  Assembly locationHint  StackCrawlMark amp  stackMark  Boolean throwOnFileNotFound  Boolean forIntrospection    I don t define any special serializers for my class   How can I fix this problem

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In Visual Studio project properties there is an option saying  generate serialization assembly   Try turning it on for a project that generates  Containing Assembly of MyType

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I ran into this exact issue and couldn t get around it by any of the solutions mentioned   Then I finally found a solution  It appears that the serializer needs not only the type  but the nested types as well  Changing this   XmlSerializer xmlSerializer   new XmlSerializer typeof T      To this   XmlSerializer xmlSerializer   new XmlSerializer typeof T  GetNestedTypes       Fixed the issue for me   No more exceptions or anything

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Had a similar problem in one of my  Net Standard dlls  I used Microsoft XmlSerializer Generator nuget  which pre-generating XmlSerializer on  Net Core and  Net Standard

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A custom class to serialise    Serializable  public class TestClass       int x   2      int y   4      public TestClass         public TestClass int x  int y                this x   x          this y   y             public int TestFunction                 return x   y            I have attached the code snippet  Maybe this can help you out   static void Main string   args        XmlSerializer xmlSerializer   new XmlSerializer typeof TestClass         MemoryStream memoryStream   new MemoryStream        XmlTextWriter xmlWriter   new XmlTextWriter memoryStream  Encoding UTF8        TestClass domain   new TestClass 10  3       xmlSerializer Serialize xmlWriter  domain       memoryStream    MemoryStream xmlWriter BaseStream      string xmlSerializedString   ConvertByteArray2Str memoryStream ToArray          TestClass xmlDomain    TestClass DeserializeObject xmlSerializedString        Console WriteLine xmlDomain TestFunction   ToString         Console ReadLine

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Like Martin Sherburn said  this is normal behavior  The constructor of the XmlSerializer first tries to find an assembly named  YourAssembly  XmlSerializers dll which should contain the generated class for serialization of your type  Since such a DLL has not been generated yet  they are not by default   a FileNotFoundException is thrown  When that happenes  XmlSerializer s constructor catches that exception  and the DLL is generated automatically at runtime by the XmlSerializer s constructor  this is done by generating C  source files in the  temp  directory of your computer  then compiling them using the C  compiler   Additional constructions of an XmlSerializer for the same type will just use the already generated DLL      UPDATE  Starting from  NET 4 5  XmlSerializer no longer performs code generation nor does it perform compilation with the C  compiler in order to create a serializer assembly at runtime  unless explicitly forced to by setting a configuration file setting  useLegacySerializerGeneration   This change removes the dependency on csc exe and improves startup performance  Source   NET Framework 4 5 Readme  section 1 3 8 1    The exception is handled by XmlSerializer s constructor  There is no need to do anything yourself  you can just click  Continue   F5  to continue executing your program and everything will be fine  If you re bothered by the exceptions stopping the execution of your program and popping up an exception helper  you either have  Just My Code  turned off  or you have the FileNotFoundException set to break execution when thrown  instead of when  User-unhandled    To enable  Just My Code   go to Tools    Options    Debugging    General    Enable Just My Code  To turn off breaking of execution when FileNotFound is thrown  go to Debug    Exceptions    Find    enter  FileNotFoundException     untick the  Thrown  checkbox from System IO FileNotFoundException

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Just as reference  Taking from D-B answer and comments  I came with this solution which is close to D-B solution  It works fine in all of my cases and it is thread safe  I don t think that using a ConcurrentDictionary would have been ok   using System  using System Collections Generic  using System Xml Serialization   namespace HQ Util General       public class XmlSerializerHelper               private static readonly Dictionary lt Type  XmlSerializer gt   dictTypeToSerializer   new Dictionary lt Type  XmlSerializer gt              public static XmlSerializer GetSerializer Type type                        lock   dictTypeToSerializer                                XmlSerializer serializer                  if     dictTypeToSerializer TryGetValue type  out serializer                                         var importer   new XmlReflectionImporter                        var mapping   importer ImportTypeMapping type  null  null                       serializer   new XmlSerializer mapping                       return  dictTypeToSerializer type    serializer                                     return serializer                                    Usage           if  File Exists Path                         using  XmlTextReader reader   new XmlTextReader Path                                    XmlSerializer x    new XmlSerializer typeof T                    var x   XmlSerializerHelper GetSerializer typeof T                     try                                       options    OptionsBase lt T gt  x Deserialize reader                                     catch  Exception ex                                        Log Instance AddEntry LogType LogException   Unable to open Options file      Path  ex

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Function XmlSerializer FromTypes does not throw the exception  but it leaks the memory  Thats why you need to cache such serializer for every type to avoid memory leaking for every instance created   Create your own XmlSerializer factory and use it simply   XmlSerializer serializer   XmlSerializerFactoryNoThrow Create typeof MyType      The factory looks likes   public static class XmlSerializerFactoryNoThrow       public static Dictionary lt Type  XmlSerializer gt   cache   new Dictionary lt Type  XmlSerializer gt          private static object SyncRootCache   new object                      lt summary gt            the constructor XmlSerializer FromTypes does not throw exception  but it is said that it causes memory leaks         http   stackoverflow com questions 1127431 xmlserializer-giving-filenotfoundexception-at-constructor         That is why I use dictionary to cache the serializers my self           lt  summary gt      public static XmlSerializer Create Type type                XmlSerializer serializer           lock  SyncRootCache                        if   cache TryGetValue type  out serializer                   return serializer                     lock  type    multiple variable of type of one type is same instance                         constructor XmlSerializer FromTypes does not throw the first chance exception                        serializer   XmlSerializer FromTypes new     type    0                 serializer   XmlSerializerFactoryNoThrow Create type                      lock  SyncRootCache                         cache type    serializer                    return serializer                   More complicated version without possibility of memory leak  please someone review the code        public static XmlSerializer Create Type type                XmlSerializer serializer           lock  SyncRootCache                        if   cache TryGetValue type  out serializer                   return serializer                     lock  type    multiple variable of type of one type is same instance                       lock  SyncRootCache                                if   cache TryGetValue type  out serializer                       return serializer                            serializer   XmlSerializer FromTypes new     type    0               lock  SyncRootCache                                 cache type    serializer                                            return serializer

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Seen a lot of recommendations to use a ConcurrentDictionary  but no solid examples of it  so I m going to throw my hat into this solution race   I m not a thread-safe developer  so if this code isn t solid  please speak up for the sake of those who follow after     public static class XmlSerializerHelper       private static readonly ConcurrentDictionary lt Type  XmlSerializer gt  TypeSerializers   new ConcurrentDictionary lt Type  XmlSerializer gt          public static XmlSerializer GetSerializer Type type                return TypeSerializers GetOrAdd type          t   gt                        var importer   new XmlReflectionImporter                var mapping   importer ImportTypeMapping t  null  null               return new XmlSerializer mapping                         I ve seen other posts involving ConcurrentDictionary and Lazy loading the value   I m not sure if that s relevant here or not  but here s the code for that     private static readonly ConcurrentDictionary lt Type  Lazy lt XmlSerializer gt  gt  TypeSerializers   new ConcurrentDictionary lt Type  Lazy lt XmlSerializer gt  gt      public static XmlSerializer GetSerializer Type type        return TypeSerializers GetOrAdd type      t   gt                var importer   new XmlReflectionImporter            var mapping   importer ImportTypeMapping t  null  null           var lazyResult   new Lazy lt XmlSerializer gt       gt  new XmlSerializer mapping   LazyThreadSafetyMode ExecutionAndPublication           return lazyResult         Value

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I was having a similar problem  and ignoring the exception did not work for me  My code was calling NServiceBus  configuration Configure With      XmlSerializer       What fixed it for me was to change the platform for my project    Go to Build Configuration Manager    Find your project and change Platform  in my case from x86 to Any CPU

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This exception can also be trapped by a managed debugging assistant  MDA  called BindingFailure     This MDA is useful if your application is designed to ship with pre-build serialization assemblies  We do this to increase performance for our application  It allows us to make sure that the pre-built serialization assemblies are being properly built by our build process  and loaded by the application without being re-built on the fly   It s really not useful except in this scenario  because as other posters have said  when a binding error is trapped by the Serializer constructor  the serialization assembly is re-built at runtime  So you can usually turn it off

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Believe it or not  this is normal behaviour  An exception is thrown but handled by the XmlSerializer  so if you just ignore it everything should continue on fine   I have found this very annoying  and there have been many complaints about this if you search around a bit  but from what I ve read Microsoft don t plan on doing anything about it   You can avoid getting Exception popups all the time while debugging if you switch off first chance exceptions for that specific exception  In Visual Studio  go to Debug -  Exceptions  or press Ctrl   Alt   E   Common Language Runtime Exceptions -  System IO -  System IO FileNotFoundException   You can find information about another way around it in the blog post C  XmlSerializer FileNotFound exception  which discusses Chris Sells  tool XmlSerializerPreCompiler

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Your type may reference other assemblies which cannot be found neither in the GAC nor in your local bin folder               or one of its dependencies  The system   cannot find the file specified    Can you give an example of the type you want to serialize   Note  Ensure that your type implements Serializable

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I had the same problem until I used a 3rd Party tool to generate the Class from the XSD and it worked   I discovered that the tool was adding some extra code at the top of my class   When I added this same code to the top of my original class it worked   Here s what I added      pragma warning disable namespace MyNamespace     using System    using System Diagnostics    using System Xml Serialization    using System Collections    using System Xml Schema    using System ComponentModel    using System Xml    using System Collections Generic      System CodeDom Compiler GeneratedCodeAttribute  System Xml    4 6 1064 2       System SerializableAttribute       System Diagnostics DebuggerStepThroughAttribute       System ComponentModel DesignerCategoryAttribute  code       System Xml Serialization XmlTypeAttribute AnonymousType   true      System Xml Serialization XmlRootAttribute Namespace       IsNullable   false     public partial class MyClassName

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I was getting the same error  and it was due to the type I was trying to deserialize not having a default parameterless constructor  I added a constructor  and it started working

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My solution is to go straight to reflection to create the serializer  This bypasses the strange file loading that causes the exception  I packaged this in a helper function that also takes care of caching the serializer   private static readonly Dictionary lt Type XmlSerializer gt   xmlSerializerCache   new Dictionary lt Type  XmlSerializer gt      public static XmlSerializer CreateDefaultXmlSerializer Type type         XmlSerializer serializer      if   xmlSerializerCache TryGetValue type  out serializer                 return serializer            else               var importer   new XmlReflectionImporter            var mapping   importer ImportTypeMapping type  null  null           serializer   new XmlSerializer mapping           return  xmlSerializerCache type    serializer

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There is a workaround for that  If you use  XmlSerializer lizer   XmlSerializer FromTypes new     typeof MyType     0     it should avoid that exception  This worked for me   WARNING  Do not use multiple times  or you will have a memory leak  You will leak memory like crazy if you use this method to create instances of XmlSerializer for the same type more than once    This is because this method bypasses the built-in caching provided the XmlSerializer type  and XmlSerializer type  defaultNameSpace  constructors  all other constructors also bypass the cache     If you use any method to create an XmlSerializer that is not via these two constructors  you must implement your own caching or you ll hemorrhage memory

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In Visual Studio project properties   Build  page  if I recall it right  there is an option saying  generate serialization assembly   Try turning it on for a project that generates  Containing Assembly of MyType

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To avoid the exception you need to do two things    Add an attribute to the serialized class  I hope you have access  Generate the serialization file with sgen exe   Add the System Xml Serialization XmlSerializerAssembly attribute to your class  Replace  MyAssembly  with the name of the assembly where MyClass is in    Serializable   XmlSerializerAssembly  MyAssembly XmlSerializers    public class MyClass           Generate the serialization file using the sgen exe utility and deploy it with the class   s assembly      sgen exe MyAssembly dll    will generate the file MyAssembly XmlSerializers dll  These two changes will cause the  net to directly find the assembly  I checked it and it works on  NET framework 3 5 with Visual Studio 2008

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Troubleshooting compilation errors on the other hand is very complicated  These problems manifest themselves in a FileNotFoundException with the message   File or assembly name abcdef dll  or one of its dependencies  was not found  File name   abcdef dll     at System Reflection Assembly nLoad           at System Reflection Assembly InternalLoad           at System Reflection Assembly Load         at System CodeDom Compiler CompilerResults get CompiledAssembly      You may wonder what a file not found exception has to do with instantiating a serializer object  but remember  the constructor writes C  files and tries to compile them  The call stack of this exception provides some good information to support that suspicion  The exception occurred while the XmlSerializer attempted to load an assembly generated by CodeDOM calling the System Reflection Assembly Load method  The exception does not provide an explanation as to why the assembly that the XmlSerializer was supposed to create was not present  In general  the assembly is not present because the compilation failed  which may happen because  under rare circumstances  the serialization attributes produce code that the C  compiler fails to compile   Note This error also occurs when the XmlSerializer runs under an account or a security environment that is not able to access the temp directory   Source  http   msdn microsoft com en-us library aa302290 aspx

[c#] XmlSerializer giving FileNotFoundException at constructor

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