Documentation:Further Linq enhancements: Difference between revisions

Further Linq enhancements

Revision as of 08:37, 15 March 2023

Until now, it has been problematic to filter on type in Linq.

The problem can be shown with this model:

If you want to find SomeSubClass that has a Class2 with a specific name:

var foo2 = (from v in EcoLinqExtender.PSQuery<Class2>(EcoSpace) 
     where (v.Class1.Attribute1 == "5" && v.Name == "5A") 
         select v.Class1)

But now, you also get Class1s that are not of SomeSubClass.That is a problem in certain situations.

In Ocl2Ps, we would have done:

Class2.allInstances->select(a|((a.Class1.Attribute1 = '5') and (a.Name = '5A'))).Class1->FilterOnType(SomeSubClass)

Until now, MDriven Linq2Sql logic did not understand the Linq counterpart of FilterOnType – which is OfType<class>().

But now it does:

var foo2 = (from v in EcoLinqExtender.PSQuery<Class2>(EcoSpace) 
       where (v.Class1.Attribute1 == "5" && v.Name == "5A") 
           select v.Class1).OfType<SomeSubClass>()

With this in place, the database takes care of all the filtering for us and returns the SomeSubClasses that have any Class2 with the correct criteria.

This page was edited more than 11 months ago on 02/10/2024. What links here

@@ Line 1: / Line 1: @@
-Up until now there has been a problem to filter on type in Linq
+Until now, it has been problematic to filter on type in Linq.
 The problem can be shown with this model:
 [[File:Linq.png|none|thumb|366x366px]]
-If you want to find SomeSubClass that has a Class2 with a specific name :<html>
+If you want to find SomeSubClass that has a Class2 with a specific name:<html>
 <pre class="code"><span style="background: white; color: blue;">var </span><span style="background: white; color: black;">foo2 = (</span><span style="background: white; color: blue;">from </span><span style="background: white; color: black;">v </span><span style="background: white; color: blue;">in </span><span style="background: white; color: #2b91af;">EcoLinqExtender</span><span style="background: white; color: black;">.PSQuery&lt;</span><span style="background: white; color: #2b91af;">Class2</span><span style="background: white; color: black;">&gt;(EcoSpace)
       </span><span style="background: white; color: blue;">where </span><span style="background: white; color: black;">(v.Class1.Attribute1 == </span><span style="background: white; color: #a31515;">"5" </span><span style="background: white; color: black;">&amp;&amp; v.Name == </span><span style="background: white; color: #a31515;">"5A"</span><span style="background: white; color: black;">)
@@ Line 11: / Line 11: @@
 </html>
-But now you also get Class1’s that are not of SomeSubClass. And that is a problem in certain situations.
+But now, you also get Class1s that are not of SomeSubClass.That is a problem in certain situations.
-In Ocl2Ps we would have done:<blockquote>''Class2.allInstances->select(a|((a.Class1.Attribute1 = '5') and (a.Name = '5A'))).Class1->FilterOnType(SomeSubClass)''</blockquote>Until now MDriven Linq2Sql logic did not understand the Linq counterpart of FilterOnType – which is OfType<class>().
+In Ocl2Ps, we would have done:<blockquote>''Class2.allInstances->select(a|((a.Class1.Attribute1 = '5') and (a.Name = '5A'))).Class1->FilterOnType(SomeSubClass)''</blockquote>Until now, MDriven Linq2Sql logic did not understand the Linq counterpart of FilterOnType – which is OfType<class>().
 But now it does:
@@ Line 24: / Line 24: @@
 </html>
-With this is place the database takes care of all the filtering for us and returns the SomeSubClasses that has any Class2 with the correct criteria.
+With this in place, the database takes care of all the filtering for us and returns the SomeSubClasses that have any Class2 with the correct criteria.
 [[Category:Linq]]