Use XmlAttributeOverrides, but get an InvalidOperationException nevertheless

Christian Treffler

Hello, I'd like to serialize an Objekt with XmlSerializer. The Objekt is a kind of treeview with lots of public properties like this:

public object Instance;

Currently I have different kind of classes stored in the Instance objects, all inheriting from the same base class. If I want to serialize these, I need to tell the XmlSerializer in an XmlAttributeOverrides object about the different Instance object classes. I collect this information dynamically before starting the XmlSerializer. Setting a breakpoint just before that I can check the Overrides object which looks like this:

- Overrides {System.Xml.Serialization.XmlAttributeOverrides} System.Xml.Serialization.XmlAttributeOverrides

```
  Non-Public members
```

  types   Count = 5   System.Collections.Hashtable

  \[{CTrModules.MDataSaveXML}\] {System.Collections.Hashtable}

  Key {Name = "MDataSaveXML" FullName = "CTrModules.MDataSaveXML"}    object {System.RuntimeType}

  Value   Count = 1   object {System.Collections.Hashtable}

  \["Instance"\]    {System.Xml.Serialization.XmlAttributes}

```
  Raw View
```

  \[{CTrModules.QSM\_Var\_Dict}\] {System.Collections.Hashtable}

  Key {Name = "QSM\_Var\_Dict" FullName = "CTrModules.QSM\_Var\_Dict"}    object {System.RuntimeType}

  Value   Count = 1   object {System.Collections.Hashtable}

  \["Instance"\]    {System.Xml.Serialization.XmlAttributes}

```
  Raw View
```

  \[{System.String}\]   {System.Collections.Hashtable}

  Key {Name = "String" FullName = "System.String"}    object {System.RuntimeType}

  Value   Count = 1   object {System.Collections.Hashtable}

  \["Instance"\]    {System.Xml.Serialization.XmlAttributes}

```
  Raw View
```

  \[{CTrModules.MHandleException}\] {System.Collections.Hashtable}

  Key {Name = "MHandleException" FullName = "CTrModules.MHandleException"}    object {System.RuntimeType}

  Value   Count = 1   object {System.Collections.Hashtable}

  \["Instance"\]    {System.Xml.Serialization.XmlAttributes}

```
  Raw View
```

  \[{FFV\_Cockpit.InternalExcHandler}\]  {System.Collections.Hashtable}

  Key {Name = "InternalExcHandler" FullName = "FFV\_Cockpit.InternalExcHandler"}   object {System.RuntimeType}

  Value   Count = 1   object {System.Collections.Hashtable}

  \["Instance"\]    {System.Xml.Serializat

Bernhard Hiller

Did you add the [XmlInclude(typeof(CTrModules.MDataSaveXML))] attribute to the base class or pass an array of types to the constructor of the serializer? See e.g. http://stackoverflow.com/questions/4923896/i-am-getting-an-error-when-trying-to-xml-serialize-an-object[^]

Christian Treffler

Hi Bernhard,

Bernhard Hiller wrote:

Did you add the [XmlInclude(typeof(CTrModules.MDataSaveXML))] attribute to the base class

I don't really want to go with that option, because then I have to remember to add such an include for any class I derive from the base class. But I tried it just for test purposes: I get the same problem. The option I chose to use is this one:

Bernhard Hiller wrote:

or pass an array of types to the constructor of the serializer?

I wrote a method to gather all types in an array and I pass this array to the serializer. I set a breakpoint at the call of the serializer and inspected this array:

- Overrides {System.Xml.Serialization.XmlAttributeOverrides} System.Xml.Serialization.XmlAttributeOverrides

```
  Non-Public members
```

  types   Count = 5   System.Collections.Hashtable

  \[{CTrModules.MDataSaveXML}\] {System.Collections.Hashtable}

  Key {Name = "MDataSaveXML" FullName = "CTrModules.MDataSaveXML"}    object {System.RuntimeType}

  Value   Count = 1   object {System.Collections.Hashtable}

  \["Instance"\]    {System.Xml.Serialization.XmlAttributes}

```
  Raw View
```

  \[{CTrModules.QSM\_Var\_Dict}\] {System.Collections.Hashtable}

  Key {Name = "QSM\_Var\_Dict" FullName = "CTrModules.QSM\_Var\_Dict"}    object {System.RuntimeType}

  Value   Count = 1   object {System.Collections.Hashtable}

  \["Instance"\]    {System.Xml.Serialization.XmlAttributes}

```
  Raw View
```

  \[{System.String}\]   {System.Collections.Hashtable}

  Key {Name = "String" FullName = "System.String"}    object {System.RuntimeType}

  Value   Count = 1   object {System.Collections.Hashtable}

  \["Instance"\]    {System.Xml.Serialization.XmlAttributes}

```
  Raw View
```

  \[{CTrModules.MHandleException}\] {System.Collections.Hashtable}

  Key {Name = "MHandleException" FullName = "CTrModules.MHandleException"}    object {System.RuntimeType}

  Value   Count = 1   object {System.Collections.Hashtable}

  \["Instance"\]    {System.Xml.Serialization.XmlAttributes}

```
  Raw View
```

  \[{FFV\_Cockpit.InternalExcHandler}\]  {System.Collections.Hashtable}

  Key {Name = "InternalExcHandler" FullName = "FFV\_Cockpit.InternalExcHandler&q