String.Replace不替换

Question

I'm doing some file clean up in an xml file and trying to use string.Replace to replace certain text blocks but it does not seem to be replacing the text that I am searching on.

My clean up code is follows

private Stream PrepareFile(string path)
{
    string data = File.ReadAllText(path);

    var newData = data.Replace("<a:FMax xmlns:b=\"http://www.w3.org/2001/XMLSchema\" i:type=\"b:string\"/>", "<a:FMax>0</a:FMax>")
        .Replace("<a:KVy xmlns:b=\"http://www.w3.org/2001/XMLSchema\" i:type=\"b:string\"/>", "<a:KVy>0</a:KVy>")
        .Replace("<a:Td xmlns:b=\"http://www.w3.org/2001/XMLSchema\" i:type=\"b:string\"/>", "<a:Td>0</a:Td>")
        .Replace("<a:VyLim xmlns:b=\"http://www.w3.org/2001/XMLSchema\" i:type=\"b:string\"/>", "<a:VyLim>0</a:VyLim>");

    var newData2 = newData.Replace("<a:VxTableSxI3_2I xmlns:b=\"http://www.w3.org/2001/XMLSchema\" i:type=\"b:string\"/>", "<a:VxTableSxI3_2I>0</a:VxTableSxI3_2I>");

    byte[] bytes = Encoding.ASCII.GetBytes(newData2);
    return new MemoryStream(bytes);
}

I should be able to write back to the original 'data' variable, but I split the variables out to be able to compare the strings before and after the replace. My xml file contains the following values(copied verbatim)

<a:LongitudinalTracker z:Id="i58">
    <Name xmlns="http://schemas.datacontract.org/2004/07/HmsSim.EntityModule.BaseTypes" i:nil="true"/>
    <a:FMax xmlns:b="http://www.w3.org/2001/XMLSchema" i:type="b:string"/>
    <a:K>2</a:K>
    <a:KVy xmlns:b="http://www.w3.org/2001/XMLSchema" i:type="b:string"/>
    <a:Td xmlns:b="http://www.w3.org/2001/XMLSchema" i:type="b:string"/>
    <a:VyLim xmlns:b="http://www.w3.org/2001/XMLSchema" i:type="b:string"/>
</a:LongitudinalTracker>

And the before and after strings look identical. I'm sure I am missing something silly, but I can't see what it is. Most of the answers to similar questions point out that the original code is not using the return value, but in this case I am definitely using the return value.

Answer 1

As suggested I am posting the code that ended up solving this.

private Stream PrepareFile(string path)
{
    string data = File.ReadAllText(path);

    var xml = XDocument.Parse(data);

    XNamespace ns = "http://schemas.datacontract.org/2004/07/HmsSim.EntityModule.Entities.SimulationEntities.Track";
    var longTracker = from item in xml.Descendants(ns + "LongitudinalTracker") select item;

    foreach (var xElement in longTracker.Elements())
    {
        XNamespace nsI = "http://www.w3.org/2001/XMLSchema-instance";
        if (xElement.Attribute(nsI + "type") != null)
        {
            xElement.Attribute(nsI + "type").Remove();
            XAttribute attribute = new XAttribute(nsI + "nil", "true");
            xElement.Add(attribute);
        }
    }

    var latTracker = from item in xml.Descendants(ns + "LateralTracker") select item;

    foreach (var xElement in latTracker.Elements())
    {
        XNamespace nsI = "http://www.w3.org/2001/XMLSchema-instance";
        if (xElement.Attribute(nsI + "type") != null)
        {
            xElement.Attribute(nsI + "type").Remove();
            XAttribute attribute = new XAttribute(nsI + "nil", "true");
            xElement.Add(attribute);
        }
    }

    Stream stream = new MemoryStream();
    xml.Save(stream);
    // Rewind the stream ready to read from it elsewhere
    stream.Position = 0;

    return stream;
}

This code works and is less brittle than the original code. As always, suggestions are welcome. Thanks to everyone who commented and led me towards this answer, I appreciate it.