How to generate a XML-file with multiple namespaces in root element with XDocument in C#?

Question

I want to generate a custom manifest.xml file for an Outlook Add-In using XDocument in C#.

My current XML file (what I want to generate now) looks as following:

<?xml version="1.0" encoding="UTF-8"?>
<OfficeApp xmlns="http://schemas.microsoft.com/office/appforoffice/1.1"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xmlns:bt="http://schemas.microsoft.com/office/officeappbasictypes/1.0"
           xmlns:mailappor="http://schemas.microsoft.com/office/mailappversionoverrides"
           xsi:type="MailApp">
  <Id>{0026EAB0-AFBA-43FE-A3FA-C479B6FEECCA}</Id>
  <Version>2.0.0.0</Version>
  <!-- More elements -->
</OfficeApp>

My main problem is, that I can't manage to add multiple namespaces to the OfficeApp-element.

I already tried the following:

private readonly XNamespace Xsi = "xsi:";
private readonly XNamespace MicrosoftSchemasAppsForOffice = "http://schemas.microsoft.com/office/appforoffice/1.1";
private readonly XNamespace W3 = "http://www.w3.org/2001/XMLSchema-instance";
private readonly XNamespace MicrosoftSchemasOfficeBasicTypes = "http://schemas.microsoft.com/office/officeappbasictypes/1.0";
private readonly XNamespace MicrosoftSchemasMailAppVersion = "http://schemas.microsoft.com/office/mailappversionoverrides";

private XDocument GenerateDocument()
{
    return new XDocument(
      new XDeclaration("1.0", "utf-8", null),
      new XElement("OfficeApp",
        new XAttribute("xmlns", MicrosoftSchemasAppsForOffice),
        new XAttribute(XNamespace.Xmlns + "xsi", W3),
        new XAttribute(XNamespace.Xmlns + "bt", MicrosoftSchemasOfficeBasicTypes),
        new XAttribute(XNamespace.Xmlns + "mailappor", MicrosoftSchemasMailAppVersion),
        new XAttribute(Xsi + "type", "MailApp"),
        new XElement("Id", "{" + Guid.NewGuid().ToString() + "}"),
        new XElement("Version", "2.0.0.0")
      )
    );
}

Which leaded to the following Exception:

System.Xml.XmlException: 'The prefix '' cannot be redefined from '' to    'http://schemas.microsoft.com/office/appforoffice/1.1' within the same start element tag.'

I also tried to replace line

new XAttribute("xmlns", MicrosoftSchemasAppsForOffice),

with

new XAttribute(XNamespace.Xmlns.NamespaceName, MicrosoftSchemasAppsForOffice),

but this gave me the following Exception:

System.Xml.XmlException: 'The ':' character, hexadecimal value 0x3A, cannot be included in a name.'

After hours of trying and failing I still don't know how to handle the xmlns-namespace properly. What am I doing wrong? I think the XML-Code I am trying to generate is valid as it works pretty fine.

I'm thankful for any hint. Thanks!

Answer 1

Your root namespace doesn't have to be added as attribute, just used as namespace for elements. Also, you have to use xsi namespace value with the type attribute:

private readonly XNamespace MicrosoftSchemasAppsForOffice = "http://schemas.microsoft.com/office/appforoffice/1.1";
private readonly XNamespace W3 = "http://www.w3.org/2001/XMLSchema-instance";
private readonly XNamespace MicrosoftSchemasOfficeBasicTypes = "http://schemas.microsoft.com/office/officeappbasictypes/1.0";
private readonly XNamespace MicrosoftSchemasMailAppVersion = "http://schemas.microsoft.com/office/mailappversionoverrides";

private XDocument GenerateDocument()
{
    return new XDocument(
      new XDeclaration("1.0", "utf-8", null),
      new XElement(MicrosoftSchemasAppsForOffice + "OfficeApp",
        new XAttribute(XNamespace.Xmlns + "xsi", W3),
        new XAttribute(XNamespace.Xmlns + "bt", MicrosoftSchemasOfficeBasicTypes),
        new XAttribute(XNamespace.Xmlns + "mailappor", MicrosoftSchemasMailAppVersion),
        new XAttribute(W3 + "type", "MailApp"),
        new XElement(MicrosoftSchemasAppsForOffice + "Id", "{" + Guid.NewGuid().ToString() + "}"),
        new XElement(MicrosoftSchemasAppsForOffice + "Version", "2.0.0.0")
      )
    );
}

Answer 2

Try getting namespace right is hard in XDocument so I normally just parse a string

            string xml = 
                "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" +
                "<OfficeApp xmlns=\"http://schemas.microsoft.com/office/appforoffice/1.1\"" +
                   " xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"" +
                   " xmlns:bt=\"http://schemas.microsoft.com/office/officeappbasictypes/1.0\"" +
                   " xmlns:mailappor=\"http://schemas.microsoft.com/office/mailappversionoverrides\"" +
                   " xsi:type=\"MailApp\">" +
                "</OfficeApp>";

            XDocument doc = XDocument.Parse(xml);
            XElement officeApp = doc.Root;
            XNamespace ns = officeApp.GetDefaultNamespace();
            officeApp.Add(new XElement(ns + "Id","{0026EAB0-AFBA-43FE-A3FA-C479B6FEECCA}"));
            officeApp.Add(new XElement(ns + "Version","2.0.0.0"));