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    <p>To respond directly to your specific question (why use <code>First</code> if you can always use <code>FirstOrDefault</code>), there are instances where you cannot use <code>FirstOrDefault</code>, because it loses information! The "default value" is likely a valid element type in the source list. You have no way to distinguish between the first element in the enumeration being null/default vs. there being no elements in the list unless you use <code>First</code> or first check if there are <code>Any</code> elements, which requires double-enumeration.</p> <p>This is especially true for value-typed enumerables, such as <code>int[]</code>. <code>default(int)</code> is <code>0</code>, which is also most likely a valid value of the array.</p> <p>In general, the two methods represent different logical flows. <code>First</code> would be used if not having any elements is "exceptional" (an error), which then want to handle out-of-band in your application. In this scenario, you "expect" to have at least one element. <code>FirstOrDefault</code> returns null on an empty set, which means you need to do additional processing with the returned value. This is similar logic to the <code>Parse</code> vs <code>TryParse</code> methods on <code>int</code>/<code>double</code>/etc. In fact, your question in some ways leads itself to the more general question of why to ever use exceptions.</p> <p>Since <code>First</code> throws an exception, it lends itself to all of the code-reuse opportunities that exceptions provide. For example, you could do:</p> <pre><code>try { x = arr1.First(); y = arr2.First(); z = arr3.First(); } catch { throw new ArgumentException(); } </code></pre>
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Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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