The process cannot access the file because it is being used by another process

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C#

I am trying to update/write to a node in an XML. I have the acception of 'The process cannot access the file because it is being used by another process'. when I googled it they say try using(..){} I did try and also I tried to change the file share mode to 'readwrite' or shut down the antivirus program taht is currently running but still I couldnt find a solution to it. I am getting the error while I am trying to write the xml it throws that an error. The code is like this:

if (agService.Status == ServiceControllerStatus.Stopped)
{
    XmlDocument xmlDoc = new XmlDocument();
    xmlDoc.Load(Application.StartupPath + "\\ReviewRules.xml");
    XmlNodeList timerNodes = xmlDoc.SelectNodes("/Settings/Timer");
    foreach (XmlNode node in timerNodes)
    {
        node["Timer"].InnerText = TimeInterval;
    }
    StringWriter sw = new StringWriter();
    XmlTextWriter xw = new XmlTextWriter(sw);
    xmlDoc.WriteTo(xw);
    
    string xml = xmlDoc.InnerXml.ToString();
    //xmlDoc.Save(Application.StartupPath + "\\ReviewRules.xml");
    //FileStream fs = File.Create(Application.StartupPath + "\\ReviewXML\\ReviewRules.xml");
    //FileStream fs = new FileStream(Application.StartupPath + "\\ReviewRules.xml", FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite);            
    //File.WriteAllText(Application.StartupPath + "\\ReviewRules.xml", xml);
    //fs.Close();
    using (FileStream fs = File.Create(Application.StartupPath + "\\ReviewRules.xml"))
    {
        File.WriteAllText(Application.StartupPath + "\\ReviewRules.xml", xml);
        fs.Close();
    }