How to: Store the Results of a Query in Memory (C# Programming Guide)
A query is basically a set of instructions for how to retrieve and organize data. To execute the query requires a call to its GetEnumerator method. This call is made when you use a foreach loop to iterate over the elements. To evaluate a query and store its results without executing a foreach loop, just call one of the following methods on the query variable:
We recommend that when you store the query results, you assign the returned collection object to a new variable as shown in the following example:
class StoreQueryResults { static List<int> numbers = new List<int>() { 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 }; static void Main() { IEnumerable<int> queryFactorsOfFour = from num in numbers where num % 4 == 0 select num; // Store the results in a new variable // without executing a foreach loop. List<int> factorsofFourList = queryFactorsOfFour.ToList(); // Iterate the list just to prove it holds data. foreach (int n in factorsofFourList) { Console.WriteLine(n); } // Keep the console window open in debug mode. Console.WriteLine("Press any key"); Console.ReadKey(); } }
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Create a Visual Studio project that targets the .NET Framework version 3.5. By default, the project has a reference to System.Core.dll and a using directive for the System.Linq namespace.
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Copy the code into your project.
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Press F5 to compile and run the program.
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Press any key to exit the console window.
