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POUsing Explicit Cast in an Extension Method
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  1. POUsing Explicit Cast in an Extension Method
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    copied!<p>I have a weird problem when I'm trying to cast an object via an extension method. I have a class where I wrap some functionality around an <code>IPAddress</code>.</p> <pre><code>// Dumbed down version of class public sealed class PrefixLengthIPAddress { public static explicit operator IPAddress(PrefixLengthIPAddress address) { return (address != null) ? address._address : null; } public PrefixLengthIPAddress(IPAddress address) { _address = address; _length = address.GetLength(); } private readonly ushort _length; private readonly IPAddress _address; } </code></pre> <p>I don't like the look of all the parenthesis to extract the <code>IPAddress</code> out of the object:</p> <pre><code>var family = ((IPAddress)prefixLengthAddress).AddressFamily; </code></pre> <p>I'd rather be able to do something like this:</p> <pre><code>var family = prefixLengthAddress.CastAs&lt;IPAddress&gt;().AddressFamily; </code></pre> <p>In order to do this I wrote the following Extension Method:</p> <pre><code>public static T CastAs&lt;T&gt;(this object value) where T : class { return (T)value; } </code></pre> <p>Unfortunately with this I'm getting an <code>InvalidCastException</code>:</p> <pre><code>var family = ((IPAddress)prefixLengthAddress).AddressFamily; // Works var family = prefixLengthAddress.CastAs&lt;IPAddress&gt;().AddressFamily; // InvalidCastException </code></pre> <p>I understand that in this particular case I could simply expose the <code>IPAddress</code> with a getter, but we also have more complex explicit casts that I would like to do this with.</p> <p><strong>EDIT</strong></p> <p>Thanks to Chris Sinclair's comment on using <code>dynamic</code> I have updated the extension method to look like:</p> <pre><code>public static T CastAs&lt;T&gt;(this object value) { return (T)((dynamic)value); } </code></pre> <p>There is some overhead with using <code>dynamic</code>, but it is more than fast enough for my needs. It also seems to work with all the basic type casting I've tried.</p>
 

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