Projection Strategies
Object Initializers
So far, all our select
clauses have projected scalar element types. With C# object
initializers, you can project into more complex types. For
example, suppose, as a first step in a query, we want to strip vowels
from a list of names while still retaining the original versions
alongside for the benefit of subsequent queries. We can write the
following class to assist:
class Temp ProjectionItem { public string Original; // Original name public string Vowelless; // Vowel-stripped name }
and then project into it with object initializers:
string[] names = { "Tom","Dick","Harry","Mary","Jay" }; IEnumerable<TempProjectionItem> temp = from n in namesselect new TempProjectionItem
{Original = n,
Vowelless = Regex.Replace (n, "[aeiou]", "")
};
The result is of type IEnumerable<TempProjectionItem >
,
which we can subsequently query:
IEnumerable<string> query = from item in temp where item.Vowelless.Length > 2 select item.Original; // RESULT: Dick, Harry, Mary
Anonymous Types
Anonymous types allow you to structure your intermediate results
without writing special classes. We can eliminate the TempProjectionItem
class in our previous
example with anonymous types:
var intermediate = from n in namesselect new
{Original = n,
Vowelless = Regex.Replace (n,"[aeiou]", "")
}; IEnumerable<string> query = from item in intermediate where item.Vowelless.Length > 2 select item.Original;
This gives the same result as the previous example, but without needing to write ...
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