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<h1>Type Safety</h1><script>
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</script><p><br></p><p>In the previous example we used generic types for our query,
constraining on only one type of objects. However LINQ is flexible enough to
allow querying across types:</p>
<span name="cs_wiki_filter" csw_filters="cs">
<div class="FormattedSourceCode"><div class="fscHeader"><span class="fscFileName">LinqExample.cs: <span class="fscMemberName">SelectEverythingByName</span></span></div><div class="fscCode"><pre ID="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65"><div><!--
Code highlighting produced by Actipro CodeHighlighter (freeware)
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--><span style="color: #008080;">01</span><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/None.gif" align="top"/><span style="color: #0000FF;">private</span><span style="color: #000000;"> </span><span style="color: #0000FF;">static</span><span style="color: #000000;"> </span><span style="color: #0000FF;">void</span><span style="color: #000000;"> SelectEverythingByName()
</span><span style="color: #008080;">02</span><span style="color: #000000;"><img id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_53_771_Open_Image" src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ExpandedBlockStart.gif" align="top" onClick="this.style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_53_771_Open_Text').style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_53_771_Closed_Image').style.display='inline'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_53_771_Closed_Text').style.display='inline';"/><img id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_53_771_Closed_Image" src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ContractedBlock.gif" align="top" style="display: none;" onClick="this.style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_53_771_Closed_Text').style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_53_771_Open_Image').style.display='inline'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_53_771_Open_Text').style.display='inline';"/> </span><span id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_53_771_Closed_Text" style="border: solid 1px #808080; background-color: #FFFFFF; display: none;">...</span><span id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_53_771_Open_Text"><span style="color: #000000;">{
</span><span style="color: #008080;">03</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> IObjectContainer container </span><span style="color: #000000;">=</span><span style="color: #000000;"> Database();
</span><span style="color: #008080;">04</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">if</span><span style="color: #000000;"> (container </span><span style="color: #000000;">!=</span><span style="color: #000000;"> </span><span style="color: #0000FF;">null</span><span style="color: #000000;">)
</span><span style="color: #008080;">05</span><span style="color: #000000;"><img id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_155_761_Open_Image" src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" onClick="this.style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_155_761_Open_Text').style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_155_761_Closed_Image').style.display='inline'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_155_761_Closed_Text').style.display='inline';"/><img id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_155_761_Closed_Image" src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ContractedSubBlock.gif" align="top" style="display: none;" onClick="this.style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_155_761_Closed_Text').style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_155_761_Open_Image').style.display='inline'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_155_761_Open_Text').style.display='inline';"/> </span><span id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_155_761_Closed_Text" style="border: solid 1px #808080; background-color: #FFFFFF; display: none;">...</span><span id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_155_761_Open_Text"><span style="color: #000000;">{
</span><span style="color: #008080;">06</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">try</span><span style="color: #000000;">
</span><span style="color: #008080;">07</span><span style="color: #000000;"><img id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_193_496_Open_Image" src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" onClick="this.style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_193_496_Open_Text').style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_193_496_Closed_Image').style.display='inline'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_193_496_Closed_Text').style.display='inline';"/><img id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_193_496_Closed_Image" src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ContractedSubBlock.gif" align="top" style="display: none;" onClick="this.style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_193_496_Closed_Text').style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_193_496_Open_Image').style.display='inline'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_193_496_Open_Text').style.display='inline';"/> </span><span id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_193_496_Closed_Text" style="border: solid 1px #808080; background-color: #FFFFFF; display: none;">...</span><span id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_193_496_Open_Text"><span style="color: #000000;">{
</span><span style="color: #008080;">08</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> var result </span><span style="color: #000000;">=</span><span style="color: #000000;"> from </span><span style="color: #0000FF;">object</span><span style="color: #000000;"> o </span><span style="color: #0000FF;">in</span><span style="color: #000000;"> container
</span><span style="color: #008080;">09</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">where</span><span style="color: #000000;"> o.ToString().StartsWith(</span><span style="color: #800000;">"</span><span style="color: #800000;">Test</span><span style="color: #800000;">"</span><span style="color: #000000;">)
</span><span style="color: #008080;">10</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> select o;
</span><span style="color: #008080;">11</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> IList objects </span><span style="color: #000000;">=</span><span style="color: #000000;"> result.ToList();
</span><span style="color: #008080;">12</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> ListResult(objects);
</span><span style="color: #008080;">13</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top"/> }</span></span><span style="color: #000000;">
</span><span style="color: #008080;">14</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">catch</span><span style="color: #000000;"> (Exception ex)
</span><span style="color: #008080;">15</span><span style="color: #000000;"><img id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_550_650_Open_Image" src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" onClick="this.style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_550_650_Open_Text').style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_550_650_Closed_Image').style.display='inline'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_550_650_Closed_Text').style.display='inline';"/><img id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_550_650_Closed_Image" src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ContractedSubBlock.gif" align="top" style="display: none;" onClick="this.style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_550_650_Closed_Text').style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_550_650_Open_Image').style.display='inline'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_550_650_Open_Text').style.display='inline';"/> </span><span id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_550_650_Closed_Text" style="border: solid 1px #808080; background-color: #FFFFFF; display: none;">...</span><span id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_550_650_Open_Text"><span style="color: #000000;">{
</span><span style="color: #008080;">16</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> System.Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">System Exception: </span><span style="color: #800000;">"</span><span style="color: #000000;"> </span><span style="color: #000000;">+</span><span style="color: #000000;"> ex.Message);
</span><span style="color: #008080;">17</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top"/> }</span></span><span style="color: #000000;">
</span><span style="color: #008080;">18</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">finally</span><span style="color: #000000;">
</span><span style="color: #008080;">19</span><span style="color: #000000;"><img id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_691_747_Open_Image" src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" onClick="this.style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_691_747_Open_Text').style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_691_747_Closed_Image').style.display='inline'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_691_747_Closed_Text').style.display='inline';"/><img id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_691_747_Closed_Image" src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ContractedSubBlock.gif" align="top" style="display: none;" onClick="this.style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_691_747_Closed_Text').style.display='none'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_691_747_Open_Image').style.display='inline'; document.getElementById('..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_691_747_Open_Text').style.display='inline';"/> </span><span id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_691_747_Closed_Text" style="border: solid 1px #808080; background-color: #FFFFFF; display: none;">...</span><span id="..LinqCs.ZipsLinqExample.Cs_LinqExample.Cs_SelectEverythingByName_239_65_691_747_Open_Text"><span style="color: #000000;">{
</span><span style="color: #008080;">20</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> CloseDatabase();
</span><span style="color: #008080;">21</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top"/> }</span></span><span style="color: #000000;">
</span><span style="color: #008080;">22</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top"/> }</span></span><span style="color: #000000;">
</span><span style="color: #008080;">23</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ExpandedBlockEnd.gif" align="top"/> }</span></span></div></pre></div></div>
</span>
<span name="cs_wiki_filter" csw_filters="vb">
<div class="FormattedSourceCode"><div class="fscHeader"><span class="fscFileName">LinqExample.vb: <span class="fscMemberName">SelectEverythingByName</span></span></div><div class="fscCode"><pre ID="..LinqVB.ZipsLinqExample.Vb_LinqExample.Vb_SelectEverythingByName_368_65"><div><!--
Code highlighting produced by Actipro CodeHighlighter (freeware)
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--><span style="color: #008080;">01</span><img id="..LinqVB.ZipsLinqExample.Vb_LinqExample.Vb_SelectEverythingByName_368_65_15_487_Open_Image" src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ExpandedBlockStart.gif" align="top" onClick="this.style.display='none'; document.getElementById('..LinqVB.ZipsLinqExample.Vb_LinqExample.Vb_SelectEverythingByName_368_65_15_487_Open_Text').style.display='none'; document.getElementById('..LinqVB.ZipsLinqExample.Vb_LinqExample.Vb_SelectEverythingByName_368_65_15_487_Closed_Image').style.display='inline'; document.getElementById('..LinqVB.ZipsLinqExample.Vb_LinqExample.Vb_SelectEverythingByName_368_65_15_487_Closed_Text').style.display='inline';"/><img id="..LinqVB.ZipsLinqExample.Vb_LinqExample.Vb_SelectEverythingByName_368_65_15_487_Closed_Image" src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ContractedBlock.gif" align="top" style="display: none;" onClick="this.style.display='none'; document.getElementById('..LinqVB.ZipsLinqExample.Vb_LinqExample.Vb_SelectEverythingByName_368_65_15_487_Closed_Text').style.display='none'; document.getElementById('..LinqVB.ZipsLinqExample.Vb_LinqExample.Vb_SelectEverythingByName_368_65_15_487_Open_Image').style.display='inline'; document.getElementById('..LinqVB.ZipsLinqExample.Vb_LinqExample.Vb_SelectEverythingByName_368_65_15_487_Open_Text').style.display='inline';"/><span style="color: #0000FF;">Private</span><span style="color: #000000;"> </span><span style="color: #0000FF;">Shared</span><span style="color: #000000;"> </span><span id="..LinqVB.ZipsLinqExample.Vb_LinqExample.Vb_SelectEverythingByName_368_65_15_487_Closed_Text" style="border: solid 1px #808080; background-color: #FFFFFF; display: none;">Sub SelectEverythingByName()</span><span id="..LinqVB.ZipsLinqExample.Vb_LinqExample.Vb_SelectEverythingByName_368_65_15_487_Open_Text"><span style="color: #0000FF;">Sub</span><span style="color: #000000;"> SelectEverythingByName()
</span><span style="color: #008080;">02</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">Dim</span><span style="color: #000000;"> container </span><span style="color: #0000FF;">As</span><span style="color: #000000;"> IObjectContainer </span><span style="color: #000000;">=</span><span style="color: #000000;"> Database()
</span><span style="color: #008080;">03</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">If</span><span style="color: #000000;"> container </span><span style="color: #0000FF;">IsNot</span><span style="color: #000000;"> </span><span style="color: #0000FF;">Nothing</span><span style="color: #000000;"> </span><span style="color: #0000FF;">Then</span><span style="color: #000000;">
</span><span style="color: #008080;">04</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">Try</span><span style="color: #000000;">
</span><span style="color: #008080;">05</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/>
</span><span style="color: #008080;">06</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">Dim</span><span style="color: #000000;"> result </span><span style="color: #000000;">=</span><span style="color: #000000;"> From o </span><span style="color: #0000FF;">In</span><span style="color: #000000;"> container Where (o.ToString().StartsWith(</span><span style="color: #800000;">"</span><span style="color: #800000;">Test</span><span style="color: #800000;">"</span><span style="color: #000000;">)) </span><span style="color: #0000FF;">Select</span><span style="color: #000000;"> o
</span><span style="color: #008080;">07</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">Dim</span><span style="color: #000000;"> objects </span><span style="color: #0000FF;">As</span><span style="color: #000000;"> IList </span><span style="color: #000000;">=</span><span style="color: #000000;"> result.ToList()
</span><span style="color: #008080;">08</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> ListResult(objects)
</span><span style="color: #008080;">09</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">Finally</span><span style="color: #000000;">
</span><span style="color: #008080;">10</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> CloseDatabase()
</span><span style="color: #008080;">11</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">End</span><span style="color: #000000;"> </span><span style="color: #0000FF;">Try</span><span style="color: #000000;">
</span><span style="color: #008080;">12</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/InBlock.gif" align="top"/> </span><span style="color: #0000FF;">End</span><span style="color: #000000;"> </span><span style="color: #0000FF;">If</span><span style="color: #000000;">
</span><span style="color: #008080;">13</span><span style="color: #000000;"><img src="../../../../Utility/ActiPro.CodeHighligher/OutliningIndicators/ExpandedBlockEnd.gif" align="top"/> </span><span style="color: #0000FF;">End Sub</span></span></div></pre></div></div>
</span>
<p>We have both Car and Pilot objects that can correspond the
selected criteria and - yes, we will get a mixed list of both. This feature is
potentially dangerous as in the development cycle you may lose control of the
objects that answer the criteria and get unexpected results. Be aware and use
untyped LINQ queries with caution.</p>
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This revision (1) was last Modified 2008-02-12T06:22:30 by Tetyana.
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