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<h1>SODA Special Cases Examples</h1>
<p>This topic contains a examples which demonstrate special behavior for some types in SODA. Take also a look at the other <a href="soda_example_catelog.htm">SODA examples</a>.</p>
<h2><a name="ContainsOnCollections"></a><a name="kanchor18"></a>Contains on Collections and Arrays</h2>
<p>Collections and arrays have a special behavior in SODA to make them easier to query. For example you can simple use a constrain directly on a collection-field to check if it contains that value.</p>
<p>Note that currently collections cannot be indexed and therefore such a constrain can be slow on a large data set.</p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IQuery query = container.Query();
query.Constrain(typeof (BlogPost));
query.Descend("tags").Constrain("db4o");
IObjectSet result = query.Execute();</pre>
<div class="codesnippet-meta">SodaQueryExamples.cs: Collection contains constrain
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<div class="codesnippet" MadCap:conditions="Primary.VB.NET">
<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim query As IQuery = container.Query()
query.Constrain(GetType(BlogPost))
query.Descend("tags").Constrain("db4o")
Dim result As IObjectSet = query.Execute()</pre>
<div class="codesnippet-meta">SodaQueryExamples.vb: Collection contains constrain
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<h2><a name="ConstrainsOnCollectionMembers"></a>Constrains on Collection Members</h2>
<p>When you have a collection or array field, you can simply descend further to the collection-member fields. This allows you query for a object, which has a collection and certain objects in that collection.</p>
<p>Note that currently collections cannot be indexed and therefore such a constrain can be slow on a large data set.</p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IQuery query = container.Query();
query.Constrain(typeof(BlogPost));
query.Descend("authors").Descend("name").Constrain("Jenny");
IObjectSet result = query.Execute();</pre>
<div class="codesnippet-meta">SodaQueryExamples.cs: Descend into collection members
<div class="codedownload"><a href="../../../CodeExamples/query/soda/Example-query-soda-csharp.zip" class="codedownload" MadCap:conditions="Primary.Online">Download Code</a></div><div class="codedownload copylink-marker" MadCap:conditions="Primary.Online"><a href="#copy">Copy Code</a></div></div>
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<div class="codesnippet" MadCap:conditions="Primary.VB.NET">
<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim query As IQuery = container.Query()
query.Constrain(GetType(BlogPost))
query.Descend("authors").Descend("name").Constrain("Jenny")
Dim result As IObjectSet = query.Execute()</pre>
<div class="codesnippet-meta">SodaQueryExamples.vb: Descend into collection members
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<h2><a name="ContainsKeyOnMaps"></a>Contains Key on <span class="PrimaryMap">Dictionary</span>s</h2>
<p>You can check a dictionary if it contains a certain key. Similar to collections, you just can directly use a constrain on the collection field. This will compare the value with the keys of the <span class="PrimaryMap">Dictionary</span>.</p>
<p>Note that currently collections cannot be indexed and therefore such a constrain can be slow on a large data set.</p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IQuery query = container.Query();
query.Constrain(typeof (BlogPost));
query.Descend("metaData").Constrain("source");
IObjectSet result = query.Execute();</pre>
<div class="codesnippet-meta">SodaQueryExamples.cs: Dictionary contains a key constrain
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<div class="codesnippet" MadCap:conditions="Primary.VB.NET">
<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim query As IQuery = container.Query()
query.Constrain(GetType(BlogPost))
query.Descend("metaData").Constrain("source")
Dim result As IObjectSet = query.Execute()</pre>
<div class="codesnippet-meta">SodaQueryExamples.vb: Dictionary contains a key constrain
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<h2><a name="FieldObjects"></a>Return the Objects of a Field</h2>
<p>With SODA you can navigate to a field and return the objects of that field. Note that this only works for reference objects and not for value objects like strings and numbers.</p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IQuery query = container.Query();
query.Constrain(typeof(Car));
query.Descend("name").Constrain("Mercedes");
// returns the pilot of these cars
IObjectSet result = query.Descend("pilot").Execute();</pre>
<div class="codesnippet-meta">SodaQueryExamples.cs: Return the object of a field
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<div class="codesnippet" MadCap:conditions="Primary.VB.NET">
<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim query As IQuery = container.Query()
query.Constrain(GetType(Car))
query.Descend("name").Constrain("Mercedes")
' returns the pilot of these cars
Dim result As IObjectSet = query.Descend("pilot").Execute()</pre>
<div class="codesnippet-meta">SodaQueryExamples.vb: Return the object of a field
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<h2><a name="MixQueryByExample"></a>Mixing With Query By Example</h2>
<p>When you have a reference type field, you can also use a <a href="../query_by_example.htm">query by example</a> constrain for that field. Pass a new object as an example for this.</p>
<p>Note that when you pass a persisted object, it will compare it by object identity and not use it as example. You can force this behavior by adding an explicit by example constrain.</p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IQuery query = container.Query();
query.Constrain(typeof(Car));
// if the given object is not stored,
// it will behave like query by example for the given object
Pilot examplePilot = new Pilot(null, 42);
query.Descend("pilot").Constrain(examplePilot);
IObjectSet carsOfPilot = query.Execute();</pre>
<div class="codesnippet-meta">SodaQueryExamples.cs: Mix with query by example
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<div class="codesnippet" MadCap:conditions="Primary.VB.NET">
<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim query As IQuery = container.Query()
query.Constrain(GetType(Car))
' if the given object is not stored,
' it will behave like query by example for the given object
Dim examplePilot As New Pilot(Nothing, 42)
query.Descend("pilot").Constrain(examplePilot)
Dim carsOfPilot As IObjectSet = query.Execute()</pre>
<div class="codesnippet-meta">SodaQueryExamples.vb: Mix with query by example
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<h2><a name="DynamicTypedNature"></a>Dynamically Typed</h2>
<p>SODA is a dynamically query language. By default SODA acts like a filter on all stored objects. You just add constrains which filters the objects to the desired output. </p>
<p>An example for this behavior: You just add an field-constraint without any <a href="soda_example_catelog.htm#TypeConstraint">type-constrain</a> on the object. This will return all objects which have such a field and match the constrain.</p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IQuery query = container.Query();
// You can simple filter objects which have a certain field
query.Descend("name").Constrain(null).Not();
IObjectSet result = query.Execute();</pre>
<div class="codesnippet-meta">SodaQueryExamples.cs: Pure field constrains
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<div class="codesnippet" MadCap:conditions="Primary.VB.NET">
<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim query As IQuery = container.Query()
' You can simple filter objects which have a certain field
query.Descend("name").Constrain(Nothing).[Not]()
Dim result As IObjectSet = query.Execute()</pre>
<div class="codesnippet-meta">SodaQueryExamples.vb: Pure field constrains
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<p>This also means that you can query for not existing fields. SODA will not complain if a field doesn't exist. Instead it won't return any object, because no object could satisfy the constrain.</p>
<div class="codesnippet" MadCap:conditions="Primary.c#">
<pre class="prettyprint" xml:space="preserve">IQuery query = container.Query();
query.Constrain(typeof (Pilot));
// using not existing fields doesn't throw an exception
// but rather exclude all object which don't use this field
query.Descend("notExisting").Constrain(null).Not();
IObjectSet result = query.Execute();</pre>
<div class="codesnippet-meta">SodaQueryExamples.cs: Using not existing fields excludes objects
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<div class="codesnippet" MadCap:conditions="Primary.VB.NET">
<pre class="prettyprint lang-vb" MadCap:conditions="Primary.Online" xml:space="preserve">Dim query As IQuery = container.Query()
query.Constrain(GetType(Pilot))
' using not existing fields doesn't throw an exception
' but rather exclude all object which don't use this field
query.Descend("notExisting").Constrain(Nothing).[Not]()
Dim result As IObjectSet = query.Execute()</pre>
<div class="codesnippet-meta">SodaQueryExamples.vb: Using not existing fields excludes objects
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