Question

I am trying to update an XML, but would like to retain the formatting{indenting} and not insert the XmlDeclaration tag. The following the snippet that I am applying.

let UpdateAndSave (configFileName:string) = 
    let xmlDoc = XDocument.Load(configFileName)
    xmlDoc.XPathEvaluate(@"Product/SomeTag/Attr[@type='Value']") :?> _
    |> Seq.cast<XElement>
    |> Seq.iter (fun elem -> elem.AddAfterSelf(XElement.Parse("<Risk type=\"123\" methodology=\"Sample\"/>")))
    do 
        let xmlWriterSettings = new XmlWriterSettings()
        xmlWriterSettings.OmitXmlDeclaration = true
        xmlWriterSettings.Indent = true
        using(XmlWriter.Create(configFileName, xmlWriterSettings))(fun xmlFileWriter -> 
        xmlDoc.Save(xmlFileWriter)
        )   
    configFileName

After the update, the xml formatting is totally lost and also the ‘XmlDeclaration’ tag gets inserted. Am I missing something?

Answer 1

In F#, = is comparison operator while <- is an assignment to a mutable field. I expect the compiler to complain that xmlWriterSettings.OmitXmlDeclaration = true is not unit value in your example.

Moreover, your do block seems redundant and using could be replaced by use for conciseness.

let xmlWriterSettings = new XmlWriterSettings()
xmlWriterSettings.OmitXmlDeclaration <- true
xmlWriterSettings.Indent <- true
use xmlWriter = XmlWriter.Create(configFileName, xmlWriterSettings)
xmlDoc.Save(xmlWriter)