My goal is to get a weighted average from one table, based on another tables primary key.

Example Data:

Table1

Key     WEIGHTED_AVERAGE

0200    0

Table2

ForeignKey    LENGTH    PCR
0200          105       52
0200          105       60
0200          105       54
0200          105       -1
0200          47        55

I need to get a weighted average based on the length of a segment and I need to ignore values of -1. I know how to do this in SQL, but my goal is to do this in LINQ. It looks something like this in SQL:

SELECT Sum(t2.PCR*t2.LENGTH)/Sum(t2.LENGTH) AS WEIGHTED_AVERAGE
FROM Table1 t1, Table2 t2
WHERE t2.PCR <> -1
AND t2.ForeinKey = t1.Key;

I am still pretty new to LINQ, and having a hard time figuring out how I would translate this. The result weighted average should come out to roughly 55.3. Thank you.