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Posted 19 Jan 2012

Dictionary Extensions: Define Useful Extensions to Play Safe

, 25 Jan 2012
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Useful extensions to play safe
if (searchCriteria.ContainsKey(key) &&
       !string.IsNullOrEmpty(searchCriteria[key]))
    searchTerm = searchCriteria[key];

Ever have a dictionary or similar data structure and your code has many repeated checks to pull the value when in reality you’d be happy with a default value like null or string.Empty? Well, consider the following extension to Dictionary:

public static class DictionaryExtensions
{
    public static TValue GetSafeValue<TKey, TValue>(this Dictionary<TKey, 
                         TValue> dictionary, TKey key)
    {
        TValue result = default(TValue);
        dictionary.TryGetValue(index, out result);
        return result;
    }
}

Let’s say you do...

Dictionary bob = new Dictionary();
string safe = bob.GetSafeValue(100);
System.Diagnostics.Trace.WriteLine(safe);

...where safe defaults to “” as it hasn’t been added. Stop! I know what you’re going to say and I thought of that too. You can control the default value as well:

public static class DictionaryExtensions
{
    /// <summary>
    /// Gets the safe value associated with the specified key.
    /// </summary>
    /// <typeparam name="TKey">The type of the key.</typeparam>
    /// <typeparam name="TValue">The type of the value.</typeparam>
    /// <param name="dictionary">The dictionary.</param>
    /// <param name="key">The key of the value to get.</param>
    public static TValue GetSafeValue<TKey, TValue>(this Dictionary<TKey, 
                         TValue> dictionary, TKey key)
    {
        return dictionary.GetSafeValue(key, default(TValue));
    }

    /// <summary>
    /// Gets the safe value associated with the specified key.
    /// </summary>
    /// <typeparam name="TKey">The type of the key.</typeparam>
    /// <typeparam name="TValue">The type of the value.</typeparam>
    /// <param name="dictionary">The dictionary.</param>
    /// <param name="key">The key of the value to get.</param>
    /// <param name="defaultValue">The default value.</param>
    public static TValue GetSafeValue<TKey, TValue>(this Dictionary<TKey, 
           TValue> dictionary, TKey key, TValue defaultValue)
    {
        TValue result;
        if (key == null || !dictionary.TryGetValue(key, out result))
            result = defaultValue;
        return result;
    }
}

Let’s say you do...

Dictionary bob = new Dictionary();
string safe = bob.GetSafeValue(100, null);
System.Diagnostics.Trace.WriteLine(safe);

...where safe is null.

There’s obviously something wrong with me because I still think this stuff is cool.

I’m developing a nice little set of extensions at this point. Often, it seems like overkill to encapsulate handy functions like these in a class. I had started by deriving a class from Dictionary<TKey, TValue> but changed over to the above.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Chris_Green
Architect Avaya Inc.
Ireland Ireland
Formerly a C++ client developer, nowadays I'm all about C# and ASP.NET. Over the years I have mastered some and played with many aspects of .NET.

Follow my blog as I catalogue the more arcane problems I encounter and their solutions at CodingLifestyle.com

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Comments and Discussions

 
QuestionIf you really want your methods to be "safe"... Pin
Qwertie24-Jan-12 16:07
memberQwertie24-Jan-12 16:07 
AnswerRe: If you really want your methods to be "safe"... Pin
newkie25-Jan-12 2:35
membernewkie25-Jan-12 2:35 
QuestionNaming Pin
Richard Deeming24-Jan-12 6:45
memberRichard Deeming24-Jan-12 6:45 
QuestionGood code! Pin
Member 308248723-Jan-12 20:58
memberMember 308248723-Jan-12 20:58 

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