modify dictionary value

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Jon Slaughter - 17 Mar 2008 20:22 GMT

How do I modify the value of a dictionary object?

I have something like

Dictionary<string, A> Q = ...

Where A is a struct.

I want to change some values in A but

Q["somestr"].x = 1;

doesn't work because it makes them read only.

If I do something like

A a = Q["somestr"];

a.x = 1;

then of course it doesn't update the value in the dictionary.

The only way I know to do it is remove the key and then re-add it with the
new value... but surely there is a better way?

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Jon Skeet [C# MVP] - 17 Mar 2008 20:37 GMT

> How do I modify the value of a dictionary object?
>
[quoted text clipped - 20 lines]
> The only way I know to do it is remove the key and then re-add it with the
> new value... but surely there is a better way?

No - or at least not without a bit of jiggery-pokery with interfaces.
But then it's a bad idea to make the struct mutable in the first place.
This is just one of the places where mutable structs are painful. Avoid
them, avoid them, avoid them.

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Jon Skeet - <skeet@pobox.com>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
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Jon Slaughter - 17 Mar 2008 21:50 GMT

>> How do I modify the value of a dictionary object?
>>
[quoted text clipped - 26 lines]
> This is just one of the places where mutable structs are painful. Avoid
> them, avoid them, avoid them.

I moved on to a keyed collection. Thats actually what I originally wanted
but didn't know it existed. (a little easier than using a dictionary because
my value was a struct in the first place).

I changed the struct to a class though so I can easily modify the values.

Thanks,
Jon

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modify dictionary value

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