Is there TryResolve in Unity?

Question

How can I make Unity not to throw ResolutionFailedException if Resolve fails?

Is there something like TryResolve<IMyInterface>?

var container = new UnityContainer();
var foo = container.TryResolve<IFoo>();
Assert.IsNull(foo);

score 16 · Answer 1 · answered Aug 25 '10 at 16:23

16

Also note that, if you're using Unity 2.0 you can use the new IsRegistered() method and it's generic version as well.

answered Aug 25 '10 at 16:23

Bryan Ray

931
10
26

10

One [big warning](https://unity.codeplex.com/discussions/392550) about the IsRegistered method: It is only meant for debugging because it is notoriously slow! It has a performance characteristic of O(n) and can completely drown the performance of your application. – Steven Aug 22 '13 at 06:45

score 9 · Accepted Answer · edited Sep 13 '17 at 19:12

This has been an issue on the codeplex site, you can find the code here (look at the bottom of that thread and they have made an extension method...very handy)

http://unity.codeplex.com/Thread/View.aspx?ThreadId=24543

and the you can use code like this:

if (container.CanResolve<T>() == true)
{
    try
    {
        return container.Resolve<T>();
    }
    catch (Exception e)
    {
        // do something else
    }
}

CanResolve is that extension method. I'm actually registering that extension upon creation of the container...something like this:

private void CreateContainer()
{
    ExeConfigurationFileMap map = new ExeConfigurationFileMap();

    map.ExeConfigFilename = // path to config file

    // get section from config code goes here

    IUnityContainer container = new UnityContainer();
    container.AddNewExtension<UnityExtensionWithTypeTracking>();
    section.Containers.Default.Configure(container);        
}

score 3 · Answer 3 · answered May 18 '09 at 18:14

3

It seems that it lacks this feature. This article shows the example of enclosing Resolve method in the try/catch block to implement it.

public object TryResolve(Type type)
{
    object resolved;

    try
    {
        resolved = Resolve(type);
    }
    catch
    {
        resolved = null;
    }

    return resolved;
}

answered May 18 '09 at 18:14

bbmud

2,678
21
15

Thanks for the great answer. I wasn't sure if my question was clear but your answer is exactly what I was looking for. – Vadim May 18 '09 at 18:20

score 2 · Answer 4 · answered May 18 '09 at 19:25

2

This is not available in the current release. However, you can always "roll your own" using extension methods in C# 3. Once Unity supports this, you can omit or update the extension method.

public static class UnityExtensions
{
    public static T TryResolve<T>( this UnityContainer container )
        where T : class
    {
        try
        {
            return (T)container.Resolve( typeof( T ) );
        }
        catch( Exception )
        {
            return null;
        }
    }
}

answered May 18 '09 at 19:25

LBushkin

129,300
32
216
265

6

Functional but expensive. Catching exception and returning null is not a good practice. – Karel Kral Feb 01 '11 at 09:09
Good way to extend, but instead of try catch, use IsRegistered method which is less expensive. – Chinjoo Apr 19 '18 at 11:45

score 0 · Answer 5 · answered Jun 02 '15 at 11:51

In Prism Unity 5, they have come up with the TryResolve function that has been included in the namespace Microsoft.Practices.Prism.UnityExtensions.

Please go through this link https://msdn.microsoft.com/en-us/library/gg419013(v=pandp.50).aspx for reference.

score 0 · Answer 6 · answered Aug 06 '20 at 14:14

0

IComponent component= null;

if (c.IsRegistered<IComponent>(registrationName))
{
  component= c.Resolve<IComponent>(registrationName);
}

return component;

answered Aug 06 '20 at 14:14

Amir Touitou

3,141
1
35
31

Is there TryResolve in Unity?

6 Answers6

Linked