C#: Filling an XML File

Question

so I already have a XML-File which got a lot of Elements, but without any value in them. Now I want do insert some Value in that already existing XML File. So I created an XmlWriter and an XmlReader. After, I started writing the XMLDocument and Copied everything from the Reader like this:

xmlWriter.WriteStartDocument();
xmlWriter.WriteNode(reader, true);

If I just leave it like that (with of course the xmlWriter.WriteEndDocument(); and xmlWriter.Close(); at the end), I will then have a new XML-File which is an exacty Copy of my default one.

My Question now is: Is it possible to add some Values and then safe this new XML-File? So basically an Copy of the default one + Values.

In Case you are wondering, what I mean by Values, I mean the "TestUser" like in the following:

<User>TestUser</User>

I´ve done some research on the Internet how to do this, but sadly I couldnt find anything.

Thanks for your help!

EDIT:

My XML looks something like this (of course larger, thats just a small example):

<users>
    <user></user>
    <user></user>
</users>

And I want this XML to be Copied with some added Values, For Example:

<users>
    <user>TestUser1</user>
    <user>TestUser2</user>
</users>

Answer 1

so you could use this class here and open the desired XML that you need keep in mind to use a object and save the new file with a diferent path or just rename the file in the _Serialize(string filePath, T object)

    public static StreamReader _StreamReader(string filePath)
    {
        try
        {
            if (string.IsNullOrEmpty(filePath))
            {
                throw new InvalidOperationException();
            }

            return new StreamReader(filePath);
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    public static void _Serialize<T>(string filePath, T object)
    {
        try
        {
            var xmlSerializer = new XmlSerializer(object.GetType());
            using (FileStream fileStream = new FileStream(filePath, FileMode.Create))
            {
                xmlSerializer.Serialize(fileStream, object);
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    public static T _UnSerialize<T>(StreamReader streamReader)
    {
        try
        {
            T deserializedObject = default(T);
            XmlSerializer xmlSerializer = new XmlSerializer(typeof(T));
            deserializedObject = (T)xmlSerializer.Deserialize(streamReader);
            streamReader.Dispose();
            return deserializedObject;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }