DtoGeneratorExtn2.cs

foreach (var pds in allProperties)
{
    var symbol = context.Compilation
            .GetSemanticModel(pds.SyntaxTree)
            .GetDeclaredSymbol(pds);
    var property = (symbol as IPropertySymbol);

    if (property.IsOfTypeClass() || property.IsOfTypeStruct())
    {
        if (property.Type.NullableAnnotation == NullableAnnotation.Annotated)
            codeBuilder.AppendLine($"\t\t\t\t\t{property.Name} = entity.{property.Name}?.ToDto() ?? null,");
        else
            codeBuilder.AppendLine($"\t\t\t\t\t{property.Name} = entity.{property.Name}.ToDto(),");
    }
    else
        codeBuilder.AppendLine($"\t\t\t\t\t{property.Name} = entity.{property.Name},");
}