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copied!<p>I agree with you that the ?? operator is usually of limited use-- it's useful to provide a fall-back value if something is null, but isn't useful to prevent a Null Reference Exception in cases when you want to continue drilling down into properties or methods of a sometimes-null reference. </p> <p>IMHO, what's needed much more than ?? is a "null-dereference" operator which allows you to chain long property and/or method chains together, e.g. <code>a.b().c.d().e</code> without having to test each intermediate step for null-ness. The <a href="http://groovy.codehaus.org/" rel="nofollow noreferrer">Groovy</a> language has a <a href="http://groovy.codehaus.org/Operators#Operators-SafeNavigationOperator(?.)" rel="nofollow noreferrer">Safe Navigation operator</a> and it's very handy.</p> <p>Luckily, it seems that the C# team is aware of this feature gap. See this <a href="http://connect.microsoft.com/VisualStudio/feedback/details/432830" rel="nofollow noreferrer">connect.microsoft.com suggestion</a> for the C# team to add a null-dereference operator to the C# language. </p> <blockquote> <p>We get quite a number of requests for features similar to this one. The "?." version mentioned in the community discussion is closest to our hearts - it allows you to test for null at every "dot", and composes nicely with the existing ?? operator:</p> <p>a?.b?.c ?? d</p> <p>Meaning if any of a , a.b or a.b.c is null use d instead.</p> <p>We are considering this for a future release, but it won't be in C# 4.0.</p> <p>Thanks again,</p> <p>Mads Torgersen, C# Language PM</p> </blockquote> <p>If you also want this feature in C#, add your votes to the <a href="http://connect.microsoft.com/VisualStudio/feedback/details/432830" rel="nofollow noreferrer">suggestion</a> on the connect site! :-)</p> <p>One workaround I use to get around the lack of this feature is an extension method like what's described in <a href="http://blogs.infosupport.com/blogs/frankb/archive/2008/02/02/Using-C_2300_-3.0-Extension-methods-and-Lambda-expressions-to-avoid-nasty-Null-Checks.aspx" rel="nofollow noreferrer">this blog post</a>, to allow code like this: </p> <pre><code>string s = h.MetaData .NullSafe(meta => meta.GetExtendedName()) .NullSafe(s => s.Trim().ToLower()) </code></pre> <p>This code either returns <code>h.MetaData.GetExtendedName().Trim().ToLower()</code> or it returns null if h, h.MetaData, or h.MetaData.GetExtendedName() is null. I've also extended this to check for null or empty strings, or null or empty collections. Here's code I use to define these extension methods:</p> <pre><code>public static class NullSafeExtensions { /// <summary> /// Tests for null objects without re-computing values or assigning temporary variables. Similar to /// Groovy's "safe-dereference" operator .? which returns null if the object is null, and de-references /// if the object is not null. /// </summary> /// <typeparam name="TResult">resulting type of the expression</typeparam> /// <typeparam name="TCheck">type of object to check for null</typeparam> /// <param name="check">value to check for null</param> /// <param name="valueIfNotNull">delegate to compute if check is not null</param> /// <returns>null if check is null, the delegate's results otherwise</returns> public static TResult NullSafe<TCheck, TResult>(this TCheck check, Func<TCheck, TResult> valueIfNotNull) where TResult : class where TCheck : class { return check == null ? null : valueIfNotNull(check); } /// <summary> /// Tests for null/empty strings without re-computing values or assigning temporary variables /// </summary> /// <typeparam name="TResult">resulting type of the expression</typeparam> /// <param name="check">value to check for null</param> /// <param name="valueIfNotNullOrEmpty">delegate to compute non-null value</param> /// <returns>null if check is null, the delegate's results otherwise</returns> public static TResult CheckNullOrEmpty<TResult>(this string check, Func<string, TResult> valueIfNotNullOrEmpty) where TResult : class { return string.IsNullOrEmpty(check) ? null : valueIfNotNullOrEmpty(check); } /// <summary> /// Tests for null/empty collections without re-computing values or assigning temporary variables /// </summary> /// <typeparam name="TResult">resulting type of the expression</typeparam> /// <typeparam name="TCheck">type of collection or array to check</typeparam> /// <param name="check">value to check for null</param> /// <param name="valueIfNotNullOrEmpty">delegate to compute non-null value</param> /// <returns>null if check is null, the delegate's results otherwise</returns> public static TResult CheckNullOrEmpty<TCheck, TResult>(this TCheck check, Func<TCheck, TResult> valueIfNotNullOrEmpty) where TCheck : ICollection where TResult : class { return (check == null || check.Count == 0) ? null : valueIfNotNullOrEmpty(check); } } </code></pre>

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