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POWeird compile-time error on Select() and ToList() LINQ methods
 

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  1. POWeird compile-time error on Select() and ToList() LINQ methods
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    <p>I have a few simple lines of code in a WPF project which give me compilation errors.</p> <pre><code>var resourceNames = new List&lt;string&gt; { "cmbItem1", "cmbItem2", "cmbItem3", "cmbItem4" }; var comboBoxItems = resourceNames.Select(id =&gt; (string)FindResource(id)).ToList(); // other code </code></pre> <p>The compilation error text is</p> <blockquote> <p><strong><em>Error 2 The type 'System.Windows.Forms.Control' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.</em></strong></p> </blockquote> <p>Why have I reference that assembly? I don't use any type from System.Windows.Forms.Control!</p> <p>If I rewrite the code to make static methods invocations instead of extension methods invocations, it works fine:</p> <pre><code>var resourceNames = new List&lt;string&gt; { "cmbItem1", "cmbItem2", "cmbItem3", "cmbItem4" }; var comboBoxItems = Enumerable.Select(resourceNames, id =&gt; (string)FindResource(id)); comboBoxItems = Enumerable.ToList(comboBoxItems); // other code </code></pre> <p>Why is it so? What am I doing wrong?</p> <p><strong><em>UPD1:</em></strong> <img src="https://i.stack.imgur.com/DtKYu.png" alt="An error is in the list."></p> <p><strong><em>UPD2: THE ANSWER</em></strong></p> <p>I and my colleague have investigated the project and found that the reason of the problem. Here are several facts about our visual studio solution:</p> <ol> <li>The problematic code resides in project called Flyer2. That project has a reference to another project called Global.</li> <li>The project Global has several classes which provide global accessible extension methods.</li> <li>One of the extension method has a restriction for a generic type in where clause. The restriction says that the generic type must be an descendant of System.Windows.Control... For some reason existence of a such method produces the compile-time error I've described...</li> </ol> <p>Here is the code of the extension method and the class defining it:</p> <pre><code>using System.Windows.Forms; namespace Global { public static class ControlExtensions { // If I remove the where-clause, the code problem disappears! public static T FindParentByType&lt;T&gt;(this Control parentControl) where T : Control { var currentControl = parentControl != null ? parentControl.Parent : null; while (currentControl != null) { if (currentControl is T) return (T)currentControl; currentControl = currentControl.Parent; } return null; } } } </code></pre>
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    1. PTQuestion
    1. USIgor Soloydenko
    1. USIgor Soloydenko
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    1. VO
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      1. POWeird compile-time error on Select() and ToList() LINQ methods
      1. USRoland Pihlakas
      1. VTFavorite
    2. VO
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      1. POWeird compile-time error on Select() and ToList() LINQ methods
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      1. VTUpMod
    1. COI don't get any compilation error on compiling first two lines
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      1. POWeird compile-time error on Select() and ToList() LINQ methods
      1. USHaris Hasan
    2. COAre you sure? Cuz, your code is working fine on my end :S
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      1. POWeird compile-time error on Select() and ToList() LINQ methods
      1. USAbdul Munim
    3. COI've attached the screenshot of the VS2010.
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      1. POWeird compile-time error on Select() and ToList() LINQ methods
      1. USIgor Soloydenko
 

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