C# 0 The Complete Reference

join

 is shown here (in context with the 

from

):

from 

range-varA 

in

data-sourceA

    join 

range-varB

 in 

data-sourceB

        on 

range-varA.property

 equals 

range-varB

.

property

The key to using 

join

 is to understand that each data source must contain data in common, 

and that data can be compared for equality. Thus, in the general form, 

data-sourceA

 and 

data-

sourceB

 must have something in common that can be compared. The items being compared 

are specified by the 

on

 section. Thus, when 

range-varA.property

 is equal to 

range-varB.property

,

the correlation succeeds. In essence, 

join

 acts like a filter, allowing only those elements that 

share a common value to pass through.

When using 

join

, often the sequence returned is a composite of portions of the two data 

sources. Therefore, 

join

 lets you generate a new list that contains elements from two 

different data sources. This enables you to organize data in a new way.

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