Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>personally I'd avoid the short circuit from operators and just let the methods chain it:</p> <pre><code>public static int CompareChain&lt;T&gt;(this int previous, T a, T b) { if (previous != 0) return previous; return Comparer&lt;T&gt;.Default.Compare(a,b); } </code></pre> <p>use like so:</p> <pre><code>int a = 0, b = 2; string x = "foo", y = "bar"; return a.Compare(b).CompareChain(x,y); </code></pre> <p>can be inlined by the JIT so it can perform just as well as short circuiting built into the language without messing about with more complexity.</p> <p>In response to your asking whether the above 'structure' can apply to more than just comparisons then yes it can, by making the choice of whether to continue or not explict and controllable by the user. This is inherently more complex but, the operation is more flexible so this is unavoidable.</p> <pre><code>public static T ElseIf&lt;T&gt;( this T previous, Func&lt;T,bool&gt; isOK Func&lt;T&gt; candidate) { if (previous != null &amp;&amp; isOK(previous)) return previous; return candidate(); } </code></pre> <p>then use like so</p> <pre><code>Connection bestConnection = server1.GetConnection() .ElseIf(IsOk, server2.GetConnection) .ElseIf(IsOk, server3.GetConnection) .ElseIf(IsOk, () =&gt; null); </code></pre> <p>This is maximum flexibility in that you can alter the <em>IsOk</em> check at any stage and are entirely lazy. For situations where the is OK check is the same in every case you can simplify like so and entirely avoid extensions methods.</p> <pre><code>public static T ElseIf&lt;T&gt;( Func&lt;T,bool&gt; isOK IEnumerable&lt;Func&lt;T&gt;[] candidates) { foreach (var candidate in candidates) { var t = candidate(); if (isOK(t)) return t; } throw new ArgumentException("none were acceptable"); } </code></pre> <p>You could do this with linq but this way gives a nice error message and allows this </p> <pre><code>public static T ElseIf&lt;T&gt;( Func&lt;T,bool&gt; isOK params Func&lt;T&gt;[] candidates) { return ElseIf&lt;T&gt;(isOK, (IEnumerable&lt;Func&lt;T&gt;&gt;)candidates); } </code></pre> <p>style which leads to nice readable code like so:</p> <pre><code>var bestConnection = ElseIf(IsOk, server1.GetConnection, server2.GetConnection, server3.GetConnection); </code></pre> <p>If you want to allow a default value then:</p> <pre><code>public static T ElseIfOrDefault&lt;T&gt;( Func&lt;T,bool&gt; isOK IEnumerable&lt;Func&lt;T&gt;&gt;[] candidates) { foreach (var candidate in candidates) { var t = candidate(); if (isOK(t)) return t; } return default(T); } </code></pre> <p>Obviously all the above can very easily be written using lambdas so your specific example would be:</p> <pre><code>var bestConnection = ElseIfOrDefault( c =&gt; c != null &amp;&amp; !(c.IsBusy || c.IsFull), server1.GetConnection, server2.GetConnection, server3.GetConnection); </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POHow-to: short-circuiting inverted ternary operator implemented in, e.g. C#? Does it matter?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USShuggyCoUk
    1. USShuggyCoUk
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POHow-to: short-circuiting inverted ternary operator implemented in, e.g. C#? Does it matter?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI'd appreciate if you helped me check my use of C# 3 above. I like where you were taking this, but wanted to cover more cases than "Comparison".
      singulars
      1. PO
      1. USmaxwellb
    2. COWow. Thanks. I knew that C# was a pretty expressive language, and that there were certainly ways to do this with a handful of methods, and so posed the original question to see if it would add anything by expressing this logic with such an operator. But, you have certainly demonstrated the expressiveness offered by the existing language very completely. The example you provided seems complete and to address any case in which the "logic operation" proposed would apply. The ElseIf generic method, and the ElseIfOrDefault methods you provide seem extremely flexible.
      singulars
      1. PO
      1. USmaxwellb
    3. COIf you enjoy this then I suggest taking a look at functional languages in general (f# being a pleasant way to do this if you are used to .Net)
      singulars
      1. PO
      1. USShuggyCoUk
 

Querying!

 
Guidance
A row detail

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.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload