Oct 27 2006

appSettings, type-safety and default values — all in 5 minute’s work

Published by sethyates at 6:00 pm under Development

I recently wanted to have a method I could call to get a type-safe AppSetting, with an optional default value if the AppSetting wasn’t set. In C# 2.0, I came up with this:
public static T GetSetting<T>(string name, T defaultValue)
{
string input = ConfigurationManager.AppSettings[name];
if (input != null)
{
return (T)Convert.ChangeType(input, typeof(T));
}
else
{
return defaultValue;
}
}

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2 Responses to “appSettings, type-safety and default values — all in 5 minute’s work”

  1. # Sonny Mon 30 Oct 2006 at 9:44 am

    Very neat use of the �GetType� method, didn�t realise it was there until now.

    Just to add some value I�ve refactored the code below so that it also checks for both empty and null, also removed the else (but thats just coding style).

    ///
    /// Gets the setting.
    ///
    /// The name.
    /// The default value.
    /// The type
    public static T GetSetting(string name, T defaultValue)
    {
    string input = ConfigurationManager.AppSettings[name];

    if (! String.IsNullOrEmpty(input))
    {
    return (T) Convert.ChangeType(input, typeof(T));
    }

    return defaultValue;
    }

    Thanks for the code snippet, I�m sure I�ll find a neat way to incorporate it into a base class.

    Cheers
    Sonny M

  2. # Sonny Mon 07 Nov 2006 at 5:47 pm

    Hi Seth,

    Not sure if it’s by design or a bug but the Convert.ChangeType method doesn’t handle nullable types.

    The below link goes into more depth into the problem and possible solution, but the supporting sample isn’t coded for web environment.

    http://72.14.253.104/search?q=cache:WWFbc_Zt-eIJ:blog.pumacode.org/+Convert.ChangeType+nullable+type+error&hl=en&gl=au&ct=clnk&cd=4

    I’ll try and post a solution, but thats if you don’t do it first.

    Cheers
    Sonny M

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