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POHow to avoid multiple nested IFs
 

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    <p>I am currently trying to restructure my program to be more OO and to better implement known patterns etc.</p> <p>I have quite many nested IF-statements and want to get rid of them. How can I go about this? My first approach was to get it done with exceptions, so e.g.</p> <pre><code>public static Boolean MyMethod(String param) { if (param == null) throw new NullReferenceException("param may not be null"); if (param.Equals("none") || param.Equals("0") || param.Equals("zero")) throw new ArgumentNullException("param may not be zero"); // Do some stuff with param // This is not executed if param is null, as the program stops a soon // as one of the above exceptions is thrown } </code></pre> <p>The method is used in the main class of the application, e.g.</p> <pre><code>static void Main() { try { Boolean test = MyClass.MyMethod(null); // Will throw an exception } catch (Exception ex) { MessageBox.Show(ex.Message, "Error"); } </code></pre> <p>I think this is quite nice, as it prevents the nested statements and nearly all of the methods actions are nicely arranged on one level.</p> <p>As with IF-statements, the method would look like this</p> <pre><code>public Boolean MyMethod(String param) { if (param != null) { if (!param.Equals("none") &amp;&amp; !param.Equals("0") &amp;&amp; !param.Equals("zero")) { // Do some stuff with param } else { MessageBox.Show("param may not be zero", "Error"); } else { MessageBox.Show("param may not be null", "Error"); } } </code></pre> <p>Which I find very, very ugly and hard to maintain.</p> <p>Now, the question is; is this approach <em>good</em>? I know, that might be subjective, but how do you overcome nested IFs (1 or 2 levels are not that bad, but it gets worse after that...)</p>
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    1. USFlorian Peschka
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    1. COThis may just be sample code, but you should really avoid throwing Exception. Use ArgumentNullException etc.
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      1. USBrian Rasmussen
    2. COAnd perhaps more importantly you should not throw and then catch exceptions like that.
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      1. USBrian Rasmussen
    3. COIt is sample code, I always try to throw better named exceptions for the case. And the catching does of course not ocurr in the same method, it's done on a very much higher level of the application, more or less just before they bubble up to the user.
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      1. USFlorian Peschka
 

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