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Argument Helper

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

Introduction

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.

Background

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

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)
{
    ArgumentHelper.AssertEnumMember<PluginType>(pluginType, 
                   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;
}

History

  • 20/3/2009 - Uploaded.

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

Andrew_Thomas
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: http://andrew.thomas.net.nz, which is all about development in Microsoft .Net, focused on C#, Asp .NET, SQL Server and SEO. Check it out...

Comments and Discussions

 
General[My vote of 2] Do better PinmemberDonsw19-Apr-09 18:13 
GeneralRe: [My vote of 2] Do better PinmemberAndrew_Thomas20-Apr-09 0:28 
The code is at the top of the article - in the attached zip.
What was brought to the table with this was the fact that its important to check arguments (which you have stated), and that in almost all code I have seen it is not done. The attached code offers a simple toolkit to allow you to add argument checking easily to your code.
What did I get out of this? Nothing except giving something back to people that it may help. Oh and also the negative comments from you, much appreciated.
GeneralRe: [My vote of 2] Do better PinmemberDonsw20-Apr-09 2:36 
GeneralMy vote of 1 PinmemberShukaido31-Mar-09 10:25 
GeneralRe: My vote of 1 PinmemberAndrew_Thomas20-Apr-09 1:09 
GeneralMy vote of 1 Pinmember_FleX20-Mar-09 14:53 
GeneralRe: My vote of 1 Pinmemberdimzon21-Mar-09 3:01 
GeneralRe: My vote of 1 PinmemberAndrew_Thomas23-Mar-09 0:03 
GeneralRe: My vote of 1 Pinmembergonalo23-Mar-09 23:55 
GeneralRe: My vote of 1 [modified] PinmemberTimMerksem24-Mar-09 7:24 
GeneralRe: My vote of 1 PinmemberAndrew_Thomas24-Mar-09 12:49 
GeneralRe: My vote of 1 Pinmemberptmcomp24-Mar-09 11:20 

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