Generics: Performance & type safety with example

Generics: Performance & type safety with example

A short note for Generics

• According to msdn “Generics are essentially a ‘code template’ that allows developers to define type-safe data structures without committing to an actual data type”.
• Introduced in .net framework 2.0

Type safety & Performance

• Generics are type safe because generics are available at run time, It means the runtime knows what type of data structure you're using and can store it in memory more efficiently.

In generics, developer can write code without incurring the cost or risk of runtime cast (boxing & unboxing) operations, so the code execution time decreases

 

Source Code

public static void GenericListPerformanceTest()
{
    var stopwatchGenericList = Stopwatch.StartNew();
    var stopwatchNonGenericList = Stopwatch.StartNew();
    var GenericList = new List<int> { 12, 89, 102, 34, 84, 67, 21 };
    var NonGenericArrayList = new ArrayList { 12, 89, 102, 34, 84, 67, 21, "Test string" };

    // Sorting generic list
    GenericList.Sort();
    stopwatchGenericList.Stop();
    Console.WriteLine($"Generic Sort" + Environment.NewLine +
        $"{nameof(GenericList)} : {GenericList}" + Environment.NewLine +
        $"Time taken: {stopwatchGenericList.Elapsed.TotalMilliseconds} ms" + Environment.NewLine);

    // Sorting non generic list
    NonGenericArrayList.Sort();
    stopwatchNonGenericList.Stop();
    Console.WriteLine($"Non-Generic Sort" + Environment.NewLine +
        $"{nameof(NonGenericArrayList)} : {NonGenericArrayList} " + Environment.NewLine +
        $"Time taken: {stopwatchNonGenericList.Elapsed.TotalMilliseconds} ms");
}

1. Performance test

 

 

Output

 

 

2. Type safety test

 

Let’s update the above code, Add a new string in GenericList, we can see a compile time error occurs for invalid type.

 

 

 

Let’s modify the same in NonGenericArrayList, we can see

1. No compile time error because arraylist store data in object type
2. But in runtime while performing the sort operation we got InvalidOperationException