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XmlSerializer InvalidOperationException using modules in v1.9.4.17
f#classes

Hi,

On moving to v1.9.4.17 XmlSerializer has started throwing an exception when attempting to serialize a type defined in a module. The exception is:

InvalidOperationException: 'ClassName' cannot be serialized. Static types cannot be used as parameters or return types.

Here is a complete example that causes this exception:

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module Test


#light


open System
open System.Xml
open System.Xml.Serialization


[<Serializable>]
type Person() =
    let mutable name = ""
    member x.Name with get() = name and set v = name <- v
    
///Takes an obj of serializable class 'ty and saves it to the given file path.
let xmlSave file (ob : 'ty)  =
  let xs = new XmlSerializer(typeof<'ty>)
  use xtr = new XmlTextWriter( (file : string), null, Formatting = Formatting.Indented ) in
    xs.Serialize(xtr, ob)    


let bob = Person(Name="Bob")
xmlSave "bob.xml" bob

This problem can be fixed by placing the Person class outside of a module so:

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namespace Test


#light


open System
open System.Xml
open System.Xml.Serialization


[<Serializable>]
type Person() =
    let mutable name = ""
    member x.Name with get() = name and set v = name <- v
    

module Utils =
    ///Takes an obj of serializable class 'ty and saves it to the given file path.
    let xmlSave file (ob : 'ty)  =
      let xs = new XmlSerializer(typeof<'ty>)
      use xtr = new XmlTextWriter( (file : string), null, Formatting = Formatting.Indented ) in
        xs.Serialize(xtr, ob)    


module Main =
    open Utils
    let bob = Person(Name="Bob")
    xmlSave "bob.xml" bob
    
open Main

This seems to preclude serializing any classes that are defined in a top-level module file. The refactored file is probably a cleaner design, but less concise.

regards,
Danny

.

I got the same issue today with the CTP. Thank you for posting the solution.

By on 10/1/2008 7:26 AM ()

Interesting, thanks for reporting this. This looks like an unexpected issue with XmlSerialziation and "static classes" in .NET. The enclosing class should be irrelevant to XmlSerialization but it seems it is not.

We'll take a look at this more closely and see if there's anything we can do: tools such as FxCop like modules to appear as sealed, static classes, so there are tradeoffs to be made here. For now the workaround you have is the best approach.

Kind regards

don

By on 6/27/2008 4:35 PM ()

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