IntelliSense doesn't show partial class method

IntelliSense doesn't show partial class method

I have partial class User generated by LINQtoSQL as shortly following:
[global::System.Data.Linq.Mapping.TableAttribute(Name="dbo.[User]")]
public partial class User : INotifyPropertyChanging, INotifyPropertyChanged
{
private static PropertyChangingEventArgs emptyChangingEventArgs = new
PropertyChangingEventArgs(String.Empty);
...
Then I created separate folder "Proxy" in my project and put there extra
piece of User class:
namespace LINQtoSQL_sample.Proxy
{
public partial class User
{
public static string GetActivationUrl()
{
return Guid.NewGuid().ToString("N");
...
Issue happens when I try to invoke that extra static method from another
part of same project. Let's say I have once more folder
"SqlRepositoryImpl" and another one partial class there:
namespace LINQtoSQL_sample.SqlRepositoryImpl
{
public partial class SqlRepository
{
public bool CreateUser(User instance)
{
if (instance.ID == 0)
{
instance.added_date = DateTime.Now;
instance.activated_link =
LINQtoSQL_sample.Proxy.User.GetActivationUrl();
...
As you can see I explicitly defined which part of User class I'm calling
for because IntelliSense didn't suggest me my extra method.
Please, advise why such happens and where I'm wrong?