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Dictionary in C#
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I am finding that as you learn to use and implement more syphistocated
programming techniques the eaiser it becomes to created what many would
call "complex algorithms". I beleive this, just think about what
alternative you have to a Dictionary. I mean other than the similiar
methods found in the System.Collections or Systems.Collections.Generic
classes. Configuration files, database selects, registry settings,
etc...all of which are not responsive enough. Having the ability to
store (Key, Value) pairs in memory, access them and change them at a
very responsive rate provides the right solution for many projects.
For example, I needed to build an HQL (NHibernate) query dynamically
based on the selection from a treeview. The treeveiw could be expanded
n levels. Plus I needed to create joins, table aliases and where clauses.
I needed to maintain counters, class names and table names during the
process.
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I chose to use a Dictionary versus a SortedList or other becuase I did
not need the data to be in any specific order, accessing it randomlly and
would not have too many items in it. It seemed to be the best choice versus
the other possibilities. That's one thing I can recommend when you are
starting you quest to become the best C# programmer in the world. Always
look at the alternatives, always have a reason why you made the decision
you did and always have reasons why you didn't choose the alternative. It
not only helps you improve your scope of understanding but will improve your
technical jargon and improve your design skills on future projects.
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There are only 3 things you really need to do with a Dictiionary. Instantiate
it, load it with data and read the data from it. Sometimes you want check
if a value exists within the dictiionary, so I will cover that too.
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Instantiating a Dictionary is performed like this:
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public static Dictionary<string, int> theDictionary =
new Dictionary<string, int>();
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I use the static keyword becuase in this instance I use it like a global
variable from within one of my classes.
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Loading the data is performed like this:
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theDictionary.Add("KEY1", 10);
theDictionary.Add("KEY2", 123);
theDictionary.Add("KEY3", 16);
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Getting the value from a key is as simple as:
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int keyValue = theDictionary["KEY2"];
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The value for keyValue would be 123.
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And finally, to check is a value exists within the Dictionary, you may
want to do this before you add a new value, NOTE: that the values stored
as the KEY must be unique and you will get an exception if you try to
store something with a duplicate key. So it is always good to check
before you add or put your add with a try..catch block and handle the
exception.
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bool exists = theDictionary.ContainsKey(("KEY1");
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In the above line, exists would be true and you would need to take
appropriate action based on your requirements.
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| Posts: 113 |
| Comments:
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| Fundamentals:
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The sample code on this website is provided to illustrate a concept and should not be used in
applications or Web sites without proper professional consultation, as it may not illustrate
the safest coding practices. I assume no liability for incidental or consequential damages
should the sample code be used for purposes other than as intended.
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