What do 2 brackets in a row mean in xaml.cs?

Just started learning C# (in xaml), so appreciate some elaboration:

((MSAvalon.Windows.Serialization.ILoaded)(_Text_2_)).DeferLoad();

Not sure what all the round brackets means... does it mean "_Text_2_" is a child of object "MSAvalon.Windows.Serialization.ILoaded" ?

and i开发者_高级运维f so... why not just something like:

MSAvalon.Windows.Serialization.ILoaded._Text_2.DeferLoad();

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_Text_2_ is casted to a MSAvalon.Windows.Serialization.ILoaded Object/Interface and then the method DeferLoad is called

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This is a typecast, used to tell the compiler that a variable is of a particular type when it's not obvious. It could have been used like this:

class Foo {
    private object _Text_2_;

    void Method() {
        ((MSAvalon.Windows.Serialization.ILoaded)_Text_2_).DeferLoad();
    }
}

Leaving out the typecast here would cause a compiler error, since DeferLoad is not a method of object. You're telling the compiler here that you have some special knowledge that _Text_2_ is really what you say it is.

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Basically it's started with (( so that DeferLoad can be called. I'll illustrate with an example.

Lets say you do the following.

object s = "Hello world";

s now contains a string. If you want to make this string uppercase using a cast (as in your example, I can't simply write this

(string)s.ToUpper();

ToUpper() can't be called, since it's not valid on a variable of type object. If you rewrite this to

((string)s).ToUpper()

it's valid. Because of the brackets, s is casted to a string first, then string.ToUpper() is called on the variable.

Note that in this case (s as string).ToUpper() would be a cleaner approach.