C# XML-Serialization -> Get rid of a hierarchy level

I have an issue with my serialization. what I need to achieve is the following xml output:

<?xml version="1.0" encoding="utf-8"?>
<Import xmlns_xsi="http://www.w3.org/2001/XMLSchema-instance" xsi_noNamespaceSchemaLocation="TR-DGU%20Import-Schema%20V2015%20-%20Stand%20M%C3%A4rz%202016.xsd">
    <creationDate>2016-05-19</creationDate>
    <hospitalCode>A-0000-A</hospitalCode>
    <importCasesWithErrors>1</importCasesWithErrors>
    <caseList>
            <case>
                <patientCode>A</patientCode>
                <intealPatientId>123456</intealPatientId>
            </case>
            <case>
                <patientCode>B</patientCode>
                <intealPatientId>asdasdasdasd</intealPatientId>
            </case>
    </caseList>
</Import>

But what I get is the following output with an additional xml level which I need to get rid of (Note the Entry "CaseNotNeeded"):

<?xml version="1.0" encoding="utf-8"?>
<Import xmlns_xsi="http://www.w3.org/2001/XMLSchema-instance" xsi_noNamespaceSchemaLocation="TR-DGU%20Import-Schema%20V2015%20-%20Stand%20M%C3%A4rz%202016.xsd">
    <creationDate>2016-05-19</creationDate>
    <hospitalCode>A-0000-A</hospitalCode>
    <importCasesWithErrors>1</importCasesWithErrors>
    <caseList>
        **<CaseNotNeeded>**
            <case>
                <patientCode>A</patientCode>
                <intealPatientId>123456</intealPatientId>
            </case>
            <case>
                <patientCode>B</patientCode>
                <intealPatientId>asdasdasdasd</intealPatientId>
            </case>
        **</CaseNotNeeded>**
    </caseList>
</Import>

I need to have a list of cases (CaseItems) in the List (CaseList) but I get always this additional entry. Anybody an idea how to get rid of that?

Any hint is very much appreciated!

My code looks like this:

CaseList.cs

namespace Serialization.Model
{
    [Serializable]
    [XmlRoot("Import")]
    public class CaseList 

    {
        [XmlArrayItem("case", typeof(CaseItem))]

        public List<CaseItem> CaseNotNeeded
        {
            get;
            set;
        }

        public CaseList()
        {
            CaseNotNeeded = new List<CaseItem>();
        }
    }
}

CaseItem.cs

namespace Serialization.Model
{
    [Serializable]
    //[XmlRoot("case")]
    public class CaseItem
    {

        [XmlElement("patientCode")]
        public string PatientCode { get; set; }

        [XmlElement("intealPatientId")]
        public string IntealPatientId { get; set; }

        public CaseItem()
        {
        }
    }
}

Import.cs

namespace Serialization.Model
{
    [Serializable]
    [XmlRootAttribute(ElementName = "Import", IsNullable = false)]
    public class Import 
    {
        [XmlAttribute("xmlns_xsi")]
        public string XMLNS { get; set; }

        [XmlAttribute("xsi_noNamespaceSchemaLocation")]
        public string XMLNSLocation { get; set; }

        [XmlElement("creationDate")]
        public string CreationDate { get; set; }

        [XmlElement("hospitalCode")]
        public string HospitalCode { get; set; }

        [XmlElement("importCasesWithErrors")]
        public int ImportCasesWithErrors { get; set; }

        [XmlElement("caseList")]
        public CaseList CaseList { get; set; }

        public Import()
        { 
        }
    }
}

and finally in the main method:

.............
.............
.............
import.CaseList = new CaseList();

CaseItem case_1 = new CaseItem();
case_1.IntealPatientId = "123456";
case_1.PatientCode = "A";
import.CaseList.CaseNotNeeded.Add(case_1);

CaseItem case_2 = new CaseItem();
case_2.IntealPatientId = "asdasdasdasd";
case_2.PatientCode = "B";
import.CaseList.CaseNotNeeded.Add(case_2);