Explicit initialization without namespace

[totpero]

Scenario 1:

I have my own declaration of SelectListItem and if i try this:

var my = new List<Base.Models.Metadate.SelectListItem>()
{
	new SelectListItem(),
       ....
}

I get ambiguous error because in my MVC app is another class with same name (https://msdn.microsoft.com/en-us/library/system.web.mvc.selectlistitem(v=vs.118).aspx)

I'm forced to use the entire namespace path explicit like this:

var my = new List<Base.Models.Metadate.SelectListItem>()
{
	new Base.Models.Metadate.SelectListItem()
}

Is not obvious and sufficient if i have List<Base.Models.Metadate.SelectListItem>() ?

Scenario 2:

If i have this explicit variable declaration also i'm forced to use all namespace when i initialize this variable:

Base.Models.Metadate.SelectListItem my = new Base.Models.Metadate.SelectListItem();

Why not using like this:

Base.Models.Metadate.SelectListItem my = new SelectListItem();

[Vlad-Stryapko]

You can make the existing case a bit simpler by namespace aliases.

using Base = Base.Models.Metadate;
...
var item = new Base.SelectListItem();

Also note the usage of var instead of explicit type, which simplifies things for your second scenario.

[vladd]

Well, but what should happen in the following setup:

var c = new NS1.Container<NS2.T2, NS3.T3>() // items are of type NS4.T4
{
    new V() // is it NS1.V, NS2.V, NS3.V or NS4.V?
};

? I'd better prefer target-typed new:

var my = new List<Base.Models.Metadate.SelectListItem>()
{
    new () // selects the item type automatically
};

[totpero]

@vladd YES, this should be much better, elegant and simple way.

[CyrusNajmabadi]

Is not obvious and sufficient if i have List<Base.Models.Metadate.SelectListItem>()

No, it is not. You may be referencing another type with that same name from some other namespace. Code like this already may exist today. We can't break the meaning of it.

[totpero]

If I have the same name from same other namespace then I can get the ambiguous error.
Why would I name my assembly/namespaces like Microsoft?

[jnm2]

Even better is what ReSharper suggests and I'm hoping Roslyn soon suggests out of the box (dotnet/roslyn#23373):

using SelectListItem = Base.Models.Metadate.SelectListItem;
// ...
var my = new List<SelectListItem>
{
    new SelectListItem()
}

With the championed target-typed new expression (#100) which I'm super excited about:

var my = new List<Base.Models.Metadate.SelectListItem>
{
    new()
}

[totpero]

In c# 9 this will be possible using Target-typed new expressions 👍