如何在运行时统一更新构造函数参数值

Question

I have the following Unity configuration section

<register type="IDbContext" mapTo="ProjectEntities" name="ProjectEntitiesContext" >
          <constructor>
            <param name="connectionString" value="conString" />
          </constructor>

Which works great. I get the value of "conString" in the connectionString parameter of my ProjectEntities class.

However, what I would like to do is change the value of the conString parameter in code.

some thing like

   myIocContaniner.registratons.ProjectEntities.Constructor.value = "Different Connection String"

And have "Different Connection String" passed to the ProjectEntities constructor when its created.

The problem I am trying to solve is making a .net WebApi interact with different data bases based on the request.

Answer 1

I'm assuming you resolve your IDbContext every time you use it (something like this)?

IDbContext myDbContext = myIocContainer.Resolve<IDbContext>("ProjectEntitiesContext");
// Some code here using myDbContext

You can just remap the type in Unity.

myIocContainer.RegisterType<IDbContext, ProjectEntities>("ProjectEntitiesContext", new InjectionConstructor("Different Connection String"));

The next time it resolves it, it'll be the new mapped type with the new injected constructor parameter.

This is also assuming you only have the connection string as a parameter to your constructor. If you have other parameters, you'll need to adjust the InjectionConstructor accordingly.