C# 0 The Complete Reference

IEnumerable

). The variable 

posNums

 is then assigned the query expression.

All queries begin with 

from

. This clause specifies two items. The first is the 

range

variable,

 which will receive elements obtained from the data source. In this case, the range 

variable is 

n

. The second item is the data source, which in this case is the 

nums

 array. The 

type of the range variable is inferred from the data source. In this case, the type of 

n

 is 

int

.

Generalizing, here is the syntax of the 

from

 clause:

from 

range-variable

 in 

data-source

The next clause in the query is 

where

. It specifies a condition that an element in the data 

source must meet in order to be obtained by the query. Its general form is shown here:

where 

boolean-expression

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The

boolean-expression 

must produce a 

bool

 result. (This expression is also called a 

predicate

.)

There can be more than one 

where

 clause in a query. In the program, this 

where

 clause is used:

where n > 0

It will be true only for an element whose value is greater than zero. This expression will be 

evaluated for every