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POPassing an IDisposable object by reference causes an error?
 

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  1. POPassing an IDisposable object by reference causes an error?
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    <p>I am trying to create a general method for disposing an object that implements <a href="http://msdn.microsoft.com/en-us/library/system.idisposable(loband).aspx" rel="nofollow noreferrer">IDisposable</a>, called <code>DisposeObject()</code><br /></p> <p>To make sure I am disposing an object pointed by original reference, I am trying to pass an object by reference.</p> <p>But I am getting a compilation error that says</p> <blockquote> <p>The 'ref' argument type doesn't match parameter type</p> </blockquote> <p>In the below (simplified) code, both <code>_Baz</code> and <code>_Bar</code> implement <a href="http://msdn.microsoft.com/en-us/library/system.idisposable(loband).aspx" rel="nofollow noreferrer">IDisposable</a>.<br /></p> <p><img src="https://farm4.static.flickr.com/3576/3479637489_d92cf9f406_o.png" alt="alt text"></p> <p>So the questions are,<br /></p> <ol> <li>Why am I getting this error?</li> <li>Is there a way to get around it?</li> </ol> <p><strong>[UPDATE]</strong> From provided answers so far, as long as I do not set an IDisposable argument to null, I can simply pass an object by value without using <code>ref</code>. I am now having another trouble whether to set disposable objects to <code>null</code> or not within <code>DisposeObject</code> method. <br /></p> <p>Here is the full source for completeness:</p> <pre><code>public class Foo : IDisposable { private Bar _Bar; private Baz _Baz; private bool _IsDisposed; ~Foo() { Dispose(false); } public void Dispose(bool disposing) { if (!_IsDisposed) { if (disposing) { DisposeObject(ref _Baz); DisposeObject(ref _Bar); } } _IsDisposed = true; } private void DisposeObject(ref IDisposable obj) { try { if (obj == null) return; obj.Dispose(); obj = null; } catch (ObjectDisposedException) { /* Already Disposed... */ } } public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } } public class Bar : IDisposable { public void Dispose() {} } public class Baz : IDisposable { public void Dispose() {} } </code></pre> <p><strong>[RESULT]</strong> <br /> I removed the code that sets argument to null (<code>obj = null;</code>) within <code>DisposeObject</code> So the final code became.</p> <pre><code> public void Dispose(bool disposing) { if (!_IsDisposed) { if (disposing) { DisposeObject(_Baz); DisposeObject(_Bar); } } _IsDisposed = true; } private void DisposeObject(IDisposable obj) { try { if (obj == null) return; obj.Dispose(); } catch (ObjectDisposedException) { /* Already Disposed... */ } } </code></pre>
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    1. USSung Kim
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    1. COI see no specific reason for using reference parameters here. Could you elaborate perhaps?
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      1. POPassing an IDisposable object by reference causes an error?
      1. USNoldorin
    2. CO@Noldorin: My initial implementation was to dispose an argument and set it to null. "obj == null;" That was the reason for "ref".
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      1. USSung Kim
    3. COobj == null is a comparison, not an assignment. obj = null is an assignment.
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      1. POPassing an IDisposable object by reference causes an error?
      1. USAdam Robinson
 

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