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Argument Helper

, 20 Mar 2009 CPOL
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An argument helper for checking arguments passed into methods.


This code example shows how to make your public methods safer to use. Especially, if they are to be used as libraries by others who don't have access to the source code.


I thought I would share some functionality to help argument checking for public methods/properties. All public/internal methods in assemblies should have appropriate argument checking and throw the appropriate exceptions:

  • ArgumentNullException – A null was passed when an argument must be specified.
  • ArgumentException – An argument passed was invalid for a certain reason.

Using the code

Obviously, the exceptions should only be thrown where appropriate, but if the code within your method requires the arguments to be in a certain state, you need to ensure it. To this end, I have added some helpers:

ArgumentHelper.AssertEnumMember<T>(enumArgument, enumValuesValid[]);
ArgumentHelper.AssertNotNull<T>(notNullArgument, " notNullArgument ");

They are pretty self explanatory, but are useful for throwing for simpler checking.

/// <summary>
/// Retrieves all available plugins based on plugin type.
/// </summary>
/// <param name="pluginType">Type of plugins to get.</param>
/// <param name="plugins">List to populate.</param>
/// <param name="pluginFile">Some plugin file.</param>
/// <param name="canBeNull">Can be null string.</param>
/// <returns>True if successful.</returns>
public static bool GetAllPlugins(PluginType pluginType, IList<string> plugins, 
                                 string pluginFile, string canBeNull)
                   new PluginType[] {PluginType.Global, PluginType.Packager}); 
    ArgumentHelper.AssertNotNull<IList<string>>(plugins, "plugins");
    ArgumentHelper.AssertNotEmptyAndNotNull(pluginFile, "pluginFile"); 

    if (canBeNull == null) //can be null so need need to check above.
      return false;


  • 20/3/2009 - Uploaded.


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


About the Author

Chief Technology Officer Intuitive Search Technologies
United Kingdom United Kingdom
Originally from New Zealand, currently work as Development Directory at a software company in the UK specialising in online marketing and advertising.
I have a blog located at:, which is all about development in Microsoft .Net, focused on C#, Asp .NET, SQL Server and SEO. Check it out...

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Comments and Discussions

General[My vote of 2] Do better Pin
Donsw19-Apr-09 18:13
memberDonsw19-Apr-09 18:13 
GeneralRe: [My vote of 2] Do better Pin
Andrew_Thomas20-Apr-09 0:28
memberAndrew_Thomas20-Apr-09 0:28 
GeneralRe: [My vote of 2] Do better Pin
Donsw20-Apr-09 2:36
memberDonsw20-Apr-09 2:36 
GeneralMy vote of 1 Pin
Shukaido31-Mar-09 10:25
memberShukaido31-Mar-09 10:25 
GeneralRe: My vote of 1 Pin
Andrew_Thomas20-Apr-09 1:09
memberAndrew_Thomas20-Apr-09 1:09 
GeneralMy vote of 1 Pin
_FleX20-Mar-09 14:53
member_FleX20-Mar-09 14:53 
should be done by test not in runtime
GeneralRe: My vote of 1 Pin
dimzon21-Mar-09 3:01
memberdimzon21-Mar-09 3:01 
GeneralRe: My vote of 1 Pin
Andrew_Thomas23-Mar-09 0:03
memberAndrew_Thomas23-Mar-09 0:03 
GeneralRe: My vote of 1 Pin
gonalo23-Mar-09 23:55
membergonalo23-Mar-09 23:55 
GeneralRe: My vote of 1 [modified] Pin
TimMerksem24-Mar-09 7:24
memberTimMerksem24-Mar-09 7:24 
GeneralRe: My vote of 1 Pin
Andrew_Thomas24-Mar-09 12:49
memberAndrew_Thomas24-Mar-09 12:49 
GeneralRe: My vote of 1 Pin
ptmcomp24-Mar-09 11:20
memberptmcomp24-Mar-09 11:20 

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