using System;

using System.Xml.Serialization;

using System.Xml;

using System.IO;

​

public class Program

{

    public static void Main()

    {

        //Arrange

        var expectedResult = "<?xml version=\"1.0\" encoding=\"utf-16\"?>\r\n<PRODUCT>\r\n <NAME>OhneWert</NAME>\r\n</PRODUCT>";

        var poco = new Product{Name = "OhneWert"};

        //Act

        var result = new ProductSerializer().Serialize<Product>(poco);

        //Assert

        if(result != expectedResult)

            throw new InvalidOperationException("Product xml should not contain nullable integer types");

    }

}

​

public class ProductSerializer 

{

    public string Serialize<T>(T objectToSerialize)

    {

        var namespaces = new XmlSerializerNamespaces();

        namespaces.Add(string.Empty, string.Empty);

        var serializer = new XmlSerializer(typeof(T));

​

        using var stringWriter = new StringWriter();

        using var writer = new XmlTextWriter(stringWriter) { Formatting = Formatting.Indented };

        serializer.Serialize(writer, objectToSerialize, namespaces);

​

        return stringWriter.ToString();

    }

}

​

[XmlType("PRODUCT")]

[Serializable]

public class Product

{

    [XmlElement(ElementName = "WERT")]

    public int? Wert { get; set; } = null!;

    [XmlElement(ElementName = "NAME")]

    public string Name { get; set; } = string.Empty;

}

​