Serialization duplicate tags c#

Concept: :
************
I am getting

<Invoice>
  <T>
    <TEST>
      <Title>1</Title>
    </TEST>
    <TEST>
      <Title>2</Title>
    </TEST>
  </T>
  <NAME>NN</NAME>
</Invoice>

And i want :


<Invoice>
    <TEST>
      <Title>1</Title>
    </TEST>
    <TEST>
      <Title>2</Title>
    </TEST>
  <NAME>NN</NAME>
</Invoice>

private void button1_Click(object sender, EventArgs e)
        {
            XMLTEST.TEST T1 = new TEST();
            T1.Title = "1";

            XMLTEST.TEST T2 = new TEST();
            T2.Title = "2";
            
            XmlTest myXML = new XmlTest();
            myXML.NAME = "NN";
            myXML.TEST=new List<TEST> { T1,T2};            
            TextWriter writer = new StreamWriter(@"C:\test.xml");        

            XmlSerializer serializer = new XmlSerializer(typeof(XmlTest));
            serializer.Serialize(writer, myXML);
            writer.Close();            
        }

                  
    }
    [XmlRoot("Invoice")]
    public class XmlTest
    {
        public string NAME
        { get; set; }
         
        public List<TEST> T;

   
      
    }
    public class TEST
    {
        public string Title
        { get; set; }
    }

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