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2

I'm using StructureMap for my DI. Imagine I have a class that takes 1 argument like:

public class ProductProvider : IProductProvider
{
     public ProductProvider(string connectionString)
     { 
         ....
     }
}

I need to specify the "connectionString at run-time when I get an instance of IProductProvider.

I have configured StructureMap as follows: 

ForRequestedType<IProductProvider>.TheDefault.Is.OfConcreteType<ProductProvider>().  
WithCtorArgument("connectionString");

However, I don't want to call EqualTo("something...") method here as I need some facility to dynamically specify this value at run-time.

My question is: how can I get an instance of IProductProvider by using ObjectFactory?

Currently, I have something like:

ObjectFactory.GetInstance<IProductProvider>();

But as you know, this doesn't work...

Any advice would be greatly appreciated.

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2 Answers

up vote 25 down vote

I suggest declaring that with the StructureMap configuration. Using the slightly newer StructureMap code:

For<IProductProvider>().Use<ProductProvider>
  .Ctor<string>("connectionString").Is(someValueAtRunTime);

This way you don't burden your client code from having to know the value and can keep your IoC configuration separate from your main code.

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up vote 21 down vote accepted

I found the answer myself! Here is the solution:

ObjectFactory.With("connectionString").EqualTo(someValueAtRunTime).GetInstance<IProductProvider>();

Hope this helps others who have come across the same issue.

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1  
Make sure that someValueAtRuntime is a simple value, not any kind of Func or Lambda (if you can do that) for retrieving it, otherwise that function will run every time the dependency is resolved. I used this trick to inject a connection string, just as you're doing. As long as you get the string into a local variable before setting up ObjectFactory, you should be fine. – Mel Aug 9 '11 at 11:59
Yo. What if I have several arguments, arg1, 2, 3 etc. And I want to pass in every argument as is but keep one of the args as null. How to do this? – J0NNY ZER0 Feb 21 at 15:31

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