Join with Substring?

[Erich]

Hi,

i have a linq statement and want in a join a substring query.
for example:

".... join e in employee on surname = l.userId.ToString().Substring(l.userId.ToString().Length-5,5) equals e.emplId into e_join ..."

It doesn't work and i can't found a substring query in a join on google ...

My problem is, the userId has a lenght of 5 with unsigned (-77704) and the emplId is signed (77704)
And i want with a substring only select the 5-digit.

Can any one help me? Please.

Thanks Erich