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POCannot use String.Empty as a default value for an optional parameter
 

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    <p>I am reading <strong>Effective C#</strong> by Bill Wagner. In <em>Item 14 - Minimize Duplicate Initialization Logic</em>, he shows the following example of using the new optional parameters feature in a constructor:</p> <p><code>public MyClass(int initialCount = 0, string name = "")</code></p> <p>Notice that he used <code>""</code> instead of <code>string.Empty</code>.<br> He comments:</p> <blockquote> <p>You'll note [in an example above] that the second constructor specified "" for the default value on the <em>name</em> parameter, rather than the more customary <code>string.Empty</code>. That's because <code>string.Empty</code> is not a compile-time constant. It is a static property defined in the string class. Because it is not a compile constant, you cannot use it for the default value for a parameter. </p> </blockquote> <p>If we cannot use the <code>string.Empty</code> static in all situations, then doesn't that defeat the purpose of it? I thought that we would use it to be sure that we have a system-independent means of referring to the empty string. Is my understanding wrong? Thanks.</p> <p>UPDATE<br> Just a follow up comment. According to MSDN:</p> <blockquote> <p>Each optional parameter has a default value as part of its definition. If no argument is sent for that parameter, the default value is used. <strong>Default values must be constants.</strong></p> </blockquote> <p>Then we aren't be able to use <code>System.Environment.NewLine</code> either, or use newly instantiated objects as default values. I haven't used VS2010 yet, and this is disappointing!</p>
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    1. COI am not aware of any differences between how empty strings are represented on different platforms. It's not like newline.
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      1. USTom Cabanski
    2. CORight, I was thinking that, so then is it just that it looks nicer in code?
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    3. COThe CLR and not the 'System' is the determining factor as to whether "" is an empty string or not. So I think you could safely assume the "" is a system-independent way of refering to a string on a compliant CLR implementation.
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      1. USChris Taylor
 

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