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:
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();
}
}
Compiling the Code
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.
Copy the code into your project.
Press F5 to compile and run the program.
Press any key to exit the console window.