What is MyAssembly.XmlSerializers.dll generated for?

Question

I am working on a project which generates an assembly. I just noticed that an additional assembly *.XmlSerializers.dll is being generated. Why this file is auto generated and what it is used for?

Vestiary

I think you already know why it is generated. if not, it is generated because your project is exposing a kind of webservice. it is always generated either during compile time or during runtime. in runtime it is generated in Temp folder with a random name – Tribunal

Answer 1

In .NET implementation, the XmlSerializer generates a temporary assembly for serializing/deserializing your classes (for performance reasons). It can either be generated on the fly (but it takes time on every execution), or it can be pregenerated during compilation and saved in this assembly you are asking about.

You can change this behaviour in project options (tab Compile -> Advanced Compile Options -> Generate serialization assemblies, Auto or On, respectively). The corresponding element in the project file is GenerateSerializationAssemblies, for example, <GenerateSerializationAssemblies>Auto</GenerateSerializationAssemblies>.

Latoya

If it's generated when the project setting is Auto, does that mean it's needed? what happens if you don't deploy the X.XMLSerializers.dll with the application, will it be generated on the fly? – Autotruck

So how does one go about pre-loading these assemblies? – Girosol

@Rory, I know this question is old, but that seems to be the case. Three of my projects were set to Auto, but only one created a serialization DLL. – Hoisch

**Generate Serialization Assemblies** Specifies whether the compiler will use the XML Serializer Generator Tool (Sgen.exe) to create XML serialization assemblies. Serialization assemblies can improve the startup performance of XmlSerializer if you have used that class to serialize types in your code. By default, this option is set to Auto, which specifies that serialization assemblies be generated only if you have used XmlSerializer to encode types in your code to XML. msdn.microsoft.com/en-us/library/kb4wyys2.aspx – Hoisch

VS2015 manual change: right click on project name -> Properties -> Build -> (Scroll down) Generate serialization assembly. – Burrow

Answer 2

FYI. The exact steps to stop the XmlSerializers.dll from being auto-generated are:

1. In VS, right-click your project file and select "Properties"
2. Click the "Build" tab
3. Change the "Generate serialization assembly" dropdown from "Auto" to "Off"
4. Rebuild and it will be gone

Wier

Yeah but the question was why it is generated! – Vestiary

I know this is an old response but in VS2015 Update 3 on a Winforms app targeting .NET 2.0 x86 when compiled on a Win10 Ent 64bit system then even when the setting "Generate serialization assembly" dropdown to "Off" then the *.XmlSerializers.dll is still generated. My app does reference a ASMX web service. Maybe a bug in VS2015 Update 3? – Rhetor

Answer 3

I think this is the JIT (Just in time) compilation of XML serialisers for performance reasons.

You get the same thing with RegEx instances using the RegexOptions.Compiled option turned on.

I'm no .NET CLR expert, sorry for lack of precise technical detail.

Clientage

Answer 4

*.XmlSerializers.dll are generated using the Sgen.exe [XML Serializer Generator Tool]

See Sgen.exe on MSDN

Typically the Sgen.exe is used in Post Build events of Projects. See if your project has a post build event which generates the *.XmlSerializers.dll

Kava

Answer 5

The project only generates the project.XMLSerialisers.dll for web applications. For other applications you have to run sgen separately.

Maddox

My WinForms app generates MyProject.XMLSerializers.dll when the setting it on or auto – Disquisition

Answer 6

I only have this when generating using a xmlRootAttrebute.

Not sure for your use-case but I used:

private static string ChangeRootName(string xmlString, string newRootName)
{
    var xmlDoc = new XmlDocument();
    xmlDoc.LoadXml(xmlString);

    // Create a new root element with the specified name
    XmlElement newRootElement = xmlDoc.CreateElement(newRootName);

    // Move all child nodes from the old root to the new root
    while (xmlDoc.DocumentElement.HasChildNodes)
    {
        newRootElement.AppendChild(xmlDoc.DocumentElement.FirstChild);
    }

    // Replace the old root with the new root
    xmlDoc.ReplaceChild(newRootElement, xmlDoc.DocumentElement);

    return xmlDoc.OuterXml;
}

And use the normal XmlSerialize and not have this issue.

Futuristic