WebService VB.NET - Return list (of) without structure TAG

I have a need to generate an XML code returned through a WebMethod () in the following format. Notice the content within the TAG <user_list> , which must have a list (of) or an arraylist without grouping:

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <s:Header xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" />
    <soap:Body>
        <ListAllUsersResult xmlns="http://teste/">
            <return_code>0</return_code>
            <return_msg>Usuarios obtidos com sucesso</return_msg>
            <user_list>
                <user_id>admin</user_id>
                <user_full_name>Admin. do Sistema</user_full_name>
                <user_id>12345</user_id>
                <user_full_name>NOME DO FUNCIONARIO 1</user_full_name>
                <user_id>678</user_id>
                <user_full_name>NOME DO FUNCIONARIO 2</user_full_name>
            </user_list>
        </ListAllUsersResult>
    </soap:Body>
</soap:Envelope>

However, when I generate XML, it comes out with a structure of my structure, placing additional TAGs. Note that the content <user_list> for each group of records adds a <st_ListUser> :

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <s:Header xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" />
    <soap:Body>
        <ListAllUsersResult xmlns="http://teste/">
            <return_code>0</return_code>
            <return_msg>Usuarios obtidos com sucesso</return_msg>
            <user_list>
                <st_ListUsers>
                    <user_id>admin</user_id>
                    <user_full_name>Admin. do Sistema</user_full_name>
                </st_ListUsers>
                <st_ListUsers>
                    <user_id>12345</user_id>
                    <user_full_name>NOME DO FUNCIONARIO 1</user_full_name>
                </st_ListUsers>
                <st_ListUsers>
                    <user_id>678</user_id>
                    <user_full_name>NOME DO FUNCIONARIO 2</user_full_name>
                </st_ListUsers>
            </user_list>
        </ListAllUsersResult>
    </soap:Body>
</soap:Envelope>

The code I use to mount this XML is as below:

   Public Structure Output_ListAllUsers
        Public return_code As String
        Public return_msg As String
        Public user_list As List(Of st_ListUsers)
    End Structure

    Public Structure st_ListUsers
        Public user_id As String
        Public user_full_name As String
    End Structure

    <SoapDocumentMethod(ParameterStyle:=SoapParameterStyle.Bare), WebMethod()>
    Public Function ListAllUsers(ByVal in_ListAllUsers As Input_ListAllUsers) As Output_ListAllUsers

        Dim obj_Return As New Output_ListAllUsers
        Dim obj_WS As New WS_functions(cc_Ambiente, _UID)

        Try

            Dim obj_WS_Result As WS_functions.st_ListAllUsers_Output = obj_WS.ListAllUsers()
            Dim obj_Users As New List(Of st_ListUsers)

            For Each dados As WS_functions.st_ListAllUsers_Users In obj_WS_Result._Users
                obj_Users.Add(New st_ListUsers With {.user_id = dados.user_id, .user_full_name = dados.user_full_name})
            Next

            obj_Return.return_code = obj_WS_Result.Cod_Process
            obj_Return.return_msg = obj_WS_Result.Desc_Process
            obj_Return.user_list = obj_Users

        Catch ex As Exception
            obj_Return.return_code = 99
            obj_Return.return_msg = ex.Message

        Finally
            ListAllUsers = obj_Return
        End Try
    End Function

Would anyone know how to guide me how do I generate XML the way I need it? I'm using VS2017 in VB and I have the need to keep in ASMX and I can not use WCF.

If you have the solution in C # it's also great!

Thank you!