Microsoft Dynamics AX (Archived)

use of as keyword

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Posted on by @rp@n

Dear All,

i read in blogs but not understand the purpose of use "as" keyword.

In standard code in SSRS reports i saw keyword "as".

Can you please let me know when and why we use "As" keyword.

What is does practically?

Please give me more shed on this.

Thanks!

Arpan

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Koen Roks on at

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Hi Arpan,

The "as" keyword can be used for casting. When we use a common buffer we can cast it to as specific table like the "custTable"

Another use of casting is up or down casting of class that use enheritance. For example if class Bar extends Foo you can always cast Foo back to Bar with the "as" keyword.

Kind regards,

Koen

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Chaitanya Golla 17,225 on at

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Hi,

as keyword is helpful to make downcast assignments explicit(For class or table inheritance) and is keyword on other hand helps to test whether this downcast is valid or not at run time.

Refer following link for detailed explanation:

(Expression Operators: Is and As for Inheritance [AX 2012])

msdn.microsoft.com/.../gg843452.aspx;MSPPError=-2147217396

(X++ Keywords [AX 2012])

msdn.microsoft.com/.../aa661012.aspx

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@rp@n 30 on at

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Thanks koen and Chaitanya

Sorry, not understand

Example :

AssetBalanceReportColumnsContract contract = this.parmDataContratc() as AssetBalanceReportColumnsContract

Can you please let me explain based on above code which using as keyword in SSRS report.

why? what is does practically ?

Please give me more shed on this.

Thanks!

Arpan

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Mahmoud Hakim 17,887 on at

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Needed when you assign a base class variable to a derived class variable. For example, given a Derived class that extends a Base class, the statement myDerived = myBase as Derived; avoids a compiler error by using the as keyword. This keyword also applies when you assign a base table variable to a derived table variable.

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@rp@n 30 on at

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Thanks Hakim,

I understand, but what is the benefit of this ?

myDerived = myBase as Derived

without using "as" we can do right?

Please give me more shed on this.

Arpan

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Rohin 4,624 on at

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Like above shared MSDN document clearly explains why we use "AS" keyword, Let me re-write here again:

"The as keyword tells other programmers and the compiler that you believe the downcast will be valid during run time."

I think you should give your time to read this.

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Mahmoud Hakim 17,887 on at

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can you check this link

msdn.microsoft.com/.../gg843452.aspx

You can use the as keyword for assignments that downcast from a base class variable to a derived class variable. The as keyword tells other programmers and the compiler that you believe the downcast will be valid during run time.

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@rp@n 30 on at

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I go through link before krishhdax.blogspot.in/.../is-and-as-keywords-introduced-in-ax2012.html

but not understand of meaning "Downcast".

please give me more shed on this.

Arpan

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Martin Dráb 237,961 Most Valuable Professional on at

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You're forgetting that you have the whole internet within arm's reach. For example, you can read about downcasting on Wikipedia.

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