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{TOC}

Back to Standard Query Operator Index


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Introduction

The Aggregate operator applies a function over a sequence. The result of the previous call to the function is passed in as an argument to the function with the next element. Optionally starts with a seed value and select projection clause.

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Method Signatures

// 1 - Call Function on Each Element
public static TSource Aggregate<TSource>(
    this IEnumerable<TSource> source, 
    Func<TSource, TSource, TSource> func)
 
// 2 - With Seed
public static TAccumulate Aggregate<TSource, TAccumulate>(
    this IEnumerable<TSource> source, 
    TAccumulate seed, 
    Func<TAccumulate, TSource, TAccumulate> func)
 
// 3 - With Seed and Select Projection
public static TResult Aggregate<TSource, TAccumulate, TResult>(
    this IEnumerable<TSource> source, 
    TAccumulate seed, Func<TAccumulate, TSource, TAccumulate> func, 
    Func<TAccumulate, TResult> resultSelector)

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Exceptions

Throws an ArgumentNullException if source or func or resultSelector is null.
Throws an InvalidOperationException if source is empty.


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Pseudo-code

If source is null throw ArgumentNullException.
If func is null throw ArgumentNullException.
If source is empty throw an InvalidOperationException.


Overload 1:
Start with the first element (first value of result).
Iterate over the source elements (starting at the second element if its there, otherwise break out of this loop)
Return result.


Overload 2:
Start with the seed value (first value of result)
Iterate over the source elements (starting at the first element)
Return result.


Overload 3:
Start with the seed value (first value of result)
Iterate over the source elements (starting at the first element)
Pass in the result to the resultSelector function and return its result.


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Loop Count

1 (the source sequence is always iterated one time)

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Code Samples

TODO: Code sample needed.