Generics at Runtime

Sunday, August 14, 2005

Here is a little test code that demonstrates how to use Generics at runtime. The code has two tests. The first test shows how to create a Generic Class at runtime. The second shows how to call a Generic method. Keep in mind that when using generics at runtime, there will be a reflection performance hit.

~ Paul

using System;
using System.Collections.ObjectModel;
using Microsoft.VisualStudio.QualityTools.UnitTesting.Framework;
using System.Reflection;
using System.Diagnostics;
namespace GenericTest
{
[TestClass]
public class GenericTest
{
[TestMethod]
public void CreateGenericAtRuntime()
{
Stopwatch watch = Stopwatch.StartNew();
// define the generic class at runtime
            Type genericType = typeof(Collection<>).MakeGenericType(typeof(DateTime));
// create an instance of the generic type
            object instance = Activator.CreateInstance(genericType);
watch.Stop();
        Console.WriteLine(</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">Dynamic Create Time: {0} ms</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">, watch.Elapsed.TotalMilliseconds);

        Assert.IsNotNull(instance, </span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">instance is Null</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">);
        Assert.IsTrue(instance </span><span style="COLOR: #0000ff">is</span><span style="COLOR: #000000"> Collection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">DateTime</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000">);

        Collection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">DateTime</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000"> dates </span><span style="COLOR: #000000">=</span><span style="COLOR: #000000"> instance </span><span style="COLOR: #0000ff">as</span><span style="COLOR: #000000"> Collection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">DateTime</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000">;

        Assert.IsNotNull(dates, </span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">dates is Null</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">);

        watch </span><span style="COLOR: #000000">=</span><span style="COLOR: #000000"> Stopwatch.StartNew();
        Collection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">DateTime</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000"> d </span><span style="COLOR: #000000">=</span><span style="COLOR: #000000"> </span><span style="COLOR: #0000ff">new</span><span style="COLOR: #000000"> Collection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">DateTime</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000">();
        watch.Stop();

        Console.WriteLine(</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">Normal Create Time: {0} ms</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">, watch.Elapsed.TotalMilliseconds);
    }

    </span><span style="COLOR: #0000ff">public</span><span style="COLOR: #000000"> Collection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">T</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000"> GetCollection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">T</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000">()
    { 
        </span><span style="COLOR: #0000ff">return</span><span style="COLOR: #000000"> </span><span style="COLOR: #0000ff">new</span><span style="COLOR: #000000"> Collection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">T</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000">(); 
    }

    [TestMethod()]
    </span><span style="COLOR: #0000ff">public</span><span style="COLOR: #000000"> </span><span style="COLOR: #0000ff">void</span><span style="COLOR: #000000"> CallGenericMethodAtRuntime()
    {
        Stopwatch watch </span><span style="COLOR: #000000">=</span><span style="COLOR: #000000"> Stopwatch.StartNew();
        MethodInfo methodInfo </span><span style="COLOR: #000000">=</span><span style="COLOR: #000000"> </span><span style="COLOR: #0000ff">typeof</span><span style="COLOR: #000000">(GenericTest).GetMethod(</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">GetCollection</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">);
        MethodInfo genericInfo </span><span style="COLOR: #000000">=</span><span style="COLOR: #000000"> methodInfo.MakeGenericMethod(</span><span style="COLOR: #0000ff">typeof</span><span style="COLOR: #000000">(DateTime));
        
        </span><span style="COLOR: #0000ff">object</span><span style="COLOR: #000000"> instance </span><span style="COLOR: #000000">=</span><span style="COLOR: #000000"> genericInfo.Invoke(</span><span style="COLOR: #0000ff">this</span><span style="COLOR: #000000">, </span><span style="COLOR: #0000ff">null</span><span style="COLOR: #000000">);
        watch.Stop();

        Console.WriteLine(</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">Dynamic Invoke Time: {0} ms</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">, watch.Elapsed.TotalMilliseconds);

        Assert.IsNotNull(instance, </span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">instance is Null</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">);
        Assert.IsTrue(instance </span><span style="COLOR: #0000ff">is</span><span style="COLOR: #000000"> Collection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">DateTime</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000">);

        Collection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">DateTime</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000"> dates </span><span style="COLOR: #000000">=</span><span style="COLOR: #000000"> instance </span><span style="COLOR: #0000ff">as</span><span style="COLOR: #000000"> Collection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">DateTime</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000">;

        Assert.IsNotNull(dates, </span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">dates is Null</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">);

        watch </span><span style="COLOR: #000000">=</span><span style="COLOR: #000000"> Stopwatch.StartNew();
        Collection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">DateTime</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000"> d </span><span style="COLOR: #000000">=</span><span style="COLOR: #000000"> </span><span style="COLOR: #0000ff">this</span><span style="COLOR: #000000">.GetCollection</span><span style="COLOR: #000000">&lt;</span><span style="COLOR: #000000">DateTime</span><span style="COLOR: #000000">&gt;</span><span style="COLOR: #000000">();
        watch.Stop();

        Console.WriteLine(</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">Normal Invoke Time: {0} ms</span><span style="COLOR: #000000">"</span><span style="COLOR: #000000">, watch.Elapsed.TotalMilliseconds);
    }
}

}

Hey Paul,

I was quite happy to see in Paul Wilson's comments just now that you've started blogging. Welcome - I hope you enjoy yourself!

I love using your O/R Mapper CS templates - so I'm looking forward to learning a little more about you.

Subscribed.

Tim.

Tim Haines - Sunday, August 14, 2005 4:05:00 AM

Oh wait - those earlier posts are from 2004 - you're an old time blogger. ;-)

Tim Haines - Sunday, August 14, 2005 4:06:00 AM

Paul,

For creation, this should work too:

this.m_GenericEntity = Activator.CreateInstance<EntityType>();

This assume that the generic type is a class (so you need a filter).

Rick Strahl - Wednesday, August 17, 2005 3:52:00 AM

3 Comments