{"id":347,"date":"2009-04-27T19:46:23","date_gmt":"2009-04-27T18:46:23","guid":{"rendered":"http:\/\/www.gamlor.info\/wordpress\/?p=347"},"modified":"2021-03-11T09:44:25","modified_gmt":"2021-03-11T08:44:25","slug":"argument-validation-utility","status":"publish","type":"post","link":"https:\/\/www.gamlor.info\/wordpress\/2009\/04\/argument-validation-utility\/","title":{"rendered":"Argument Validation Utility"},"content":{"rendered":"

A while ago I\u2019ve found a nice way to implement argument validation on the Paint.Net-blog<\/a>. Its a fluent-interface like this:<\/p>\n

\n
public<\/span> void<\/span> CallMe(object<\/span> sender,int<\/span> size, string<\/span> name)\r\n{\r\n    Validate.Begin()\r\n        .IsType<Guid>(sender, \"sender\"<\/span>)\r\n        .BiggerThan(size, 0, \"size\"<\/span>)\r\n        .IsNotEmpty(name, \"name\"<\/span>)\r\n        .Check();\r\n    \/*IMPL *\/<\/span>\r\n}<\/pre>\n<\/blockquote>\n
If only condition fails,<\/p>\n
CallMe(Guid.NewGuid(), 2, “”<\/span>);<\/p><\/blockquote>\n
you get a normal exception:<\/p>\n
System.ArgumentException: The argument ‘name’ cannot be empty<\/p><\/blockquote>\n
But if more than one condition fails,<\/p>\n
CallMe(“I’m not a guid”, 0, null);<\/p><\/blockquote>\n
you get an exception which reports each violation:<\/p>\n
Core.IoC.Utils.MultiException: Validation failed with multiple causes:<\/p>\n
The parameter ‘sender’ is not of type: ‘System.Guid’. Instance: ‘I’m not a guid’ of type: System.String<\/p>\n
Expected that the argument ‘size’ is bigger than 0 but is is 0<\/p>\n
Value cannot be null. Parameter name: name<\/p><\/blockquote>\n
Its even possible to iterate over the inner exceptions if necessary:<\/p>\n
\n
try<\/span>{\r\n    CallMe(\"I'm not a guid\"<\/span>, 0, null<\/span>);\r\n} catch<\/span>(MultiException ex)\r\n{\r\n    foreach<\/span> (var singleException in<\/span> ex.InnerExceptions)\r\n    {\r\n        Console.Out.WriteLine(singleException);\r\n    }\r\n}<\/pre>\n<\/blockquote>\n
Now to the clever implementation. All the checks are actually extension-methods, which extend the Validation-class. Now, the initial Validate.Begin()-Method return null! Each validation-method first checks its validation. If it fails, it checks if a Validation-class instance is there or not. If so, it adds its exception, if not, it creates the Validation class instance. The final Check-method then tests if there is actually a Validation class instance and throws the exceptions if necessary. With this clever trick, the validation-checks never allocate any object until there is an exception to throw (more detailed on the Paint.Net-blog<\/a>)<\/p>\n
\n
\n
public<\/span> static<\/span> class<\/span> Validate\r\n{\r\n\r\n    public<\/span> static<\/span> Validation Begin()\r\n    {\r\n        return<\/span> null<\/span>;\r\n    }\r\n}\r\n\r\npublic<\/span> sealed<\/span> class<\/span> Validation\r\n{\r\n    private<\/span> readonly<\/span> List<Exception> exceptions = new<\/span> List<Exception>(1);\r\n\r\n    internal<\/span> Validation()\r\n    {\r\n    }\r\n\r\n    internal<\/span> IEnumerable<Exception> Exceptions\r\n    {\r\n        get { return<\/span> exceptions; }\r\n    }\r\n\r\n    internal<\/span> Validation AddException(Exception ex)\r\n    {\r\n        exceptions.Add(ex);\r\n        return<\/span> this<\/span>;\r\n    }\r\n}\r\n\r\npublic<\/span> static<\/span> class<\/span> ValidationExtensions\r\n{\r\n    \/\/\/ *snip* documentation<\/span>\r\n    public<\/span> static<\/span> Validation IsNotNull<T>(this<\/span> Validation validation, T theObject, string<\/span> argumentName) where<\/span> T : class<\/span>\r\n    {\r\n        if<\/span> (theObject == null<\/span>)\r\n        {\r\n            return<\/span> (validation ?? new<\/span> Validation()).AddException(new<\/span> ArgumentNullException(argumentName));\r\n        }\r\n        return<\/span> validation;\r\n    }\r\n\r\n    \/* more checks *\/<\/span>\r\n\r\n    \/\/\/ *snip* documentation<\/span>\r\n    public<\/span> static<\/span> Validation Check(this<\/span> Validation validation)\r\n    {\r\n        if<\/span> (validation == null<\/span>) return<\/span> validation;\r\n        {\r\n            if<\/span> (validation.Exceptions.Take(2).Count() == 1)\r\n            {\r\n                throw<\/span> validation.Exceptions.First();\r\n            }\r\n            var messages = new<\/span> StringBuilder(\"Validation Failed with multiple causes:\"<\/span>);\r\n            messages.AppendLine();\r\n            foreach<\/span> (var exception in<\/span> validation.Exceptions)\r\n            {\r\n                messages.AppendLine(exception.Message);\r\n            }\r\n            throw<\/span> new<\/span> MultiException(messages.ToString(), validation.Exceptions);\r\n        }\r\n    }\r\n}\r\n\r\n[Serializable]\r\npublic<\/span> class<\/span> MultiException : ArgumentException\r\n{\r\n\r\n    internal<\/span> MultiException(string<\/span> message, IEnumerable<Exception> exceptions) : base<\/span>(message)\r\n    {\r\n        InnerExceptions = exceptions;\r\n    }\r\n\r\n    \/* snip some irrelavant stuff *\/<\/span>\r\n\r\n    public<\/span> IEnumerable<Exception> InnerExceptions { get; private<\/span> set; }\r\n\r\n    \/* snip serialisation-stuff *\/<\/span>\r\n}<\/pre>\n<\/div>\n<\/blockquote>\n
As far as I know with .NET 4.0 some kind of contracts<\/a> will be introduced to the core framework. Then I will start to use those, to benefit from the better tool support.<\/p>\n","protected":false},"excerpt":{"rendered":"
A while ago I\u2019ve found a nice way to implement argument validation on the Paint.Net-blog. Its a fluent-interface like this: public void CallMe(object sender,int size, string name) { Validate.Begin() .IsType<Guid>(sender,… <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_links_to":"","_links_to_target":""},"categories":[126,17],"tags":[21,24],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.gamlor.info\/wordpress\/wp-json\/wp\/v2\/posts\/347"}],"collection":[{"href":"https:\/\/www.gamlor.info\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.gamlor.info\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.gamlor.info\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.gamlor.info\/wordpress\/wp-json\/wp\/v2\/comments?post=347"}],"version-history":[{"count":8,"href":"https:\/\/www.gamlor.info\/wordpress\/wp-json\/wp\/v2\/posts\/347\/revisions"}],"predecessor-version":[{"id":3754,"href":"https:\/\/www.gamlor.info\/wordpress\/wp-json\/wp\/v2\/posts\/347\/revisions\/3754"}],"wp:attachment":[{"href":"https:\/\/www.gamlor.info\/wordpress\/wp-json\/wp\/v2\/media?parent=347"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.gamlor.info\/wordpress\/wp-json\/wp\/v2\/categories?post=347"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.gamlor.info\/wordpress\/wp-json\/wp\/v2\/tags?post=347"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}