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POException raised when using a Linq query with Entity Framework
 

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    <p><em>I removed a substantial amount of text from this question because I feel it needed to be more succinct. - Serg</em></p> <p>Here's what I'm trying to do. User selects a State, then a ComboBox loads with Cities in that State, then when user selects a Сity a ListBox loads all projects from that City.</p> <p>When running the method that's supposed to load the projects to the ComboBox, I receive this error:</p> <blockquote> <p>Exception has been thrown by the target of an invocation. Inner Exception is: "{"Specified cast is not valid."}"valid."}"</p> </blockquote> <p>This is the method that causes the exception:</p> <pre><code>private void LoadProjectsToListBox(long idCity) { ProjectRepository projectRepo = new ProjectRepository(); //This line causes the error. var projects = projectRepo.FindAllProjects().Where(c =&gt; c.IDCity == 1).ToList(); } </code></pre> <p>In the Linq query, you'll see that I'm comparing against a hard coded number. 1, is a valid ID of a City that has Projects so it should work. The exception is only raised when I give the Linq query a City ID that has Projects. So it seems the error is raised when the query returns results.</p> <p>Here is the SQL statements I used to generate the Project and City tables:</p> <pre><code>create table City ( ID integer primary key autoincrement, Name string, IDState integer references State(ID) ); create table Project ( ID integer primary key autoincrement, Name string, StartDate text, IDManager integer references Manager(ID), IDCity integer references City(ID), IDDepartment integer references Department(ID), ContactNumber string, Description string ); </code></pre> <p>What strikes me as odd is that using the <strong>exact same pattern and access code</strong> to show a list of Departments (just another table in my database) everything works as expected. For example here's how I load Departments right now just for testing:</p> <pre><code>private void LoadProjectsToListBox(long idCity) { ProjectRepository projectRepo = new ProjectRepository(); DepartmentRepository departmentRepo = new DepartmentRepository(); //Doesn't work - raises exception. var projects = projectRepo.FindAllProjects().Where(c =&gt; c.IDCity == 1).ToList(); //Works exactly as expected. var deps = departmentRepo.FindAllDepartments().Where(c =&gt; c.IDParentDepartment == 7).ToList(); lstProjects.Items.Clear(); foreach (var item in deps) { lstProjects.Items.Add(item.Name); } } </code></pre> <p><strong>Edit:</strong></p> <p>The FindAllDepartments(), FindAllCities(), FindAllProjects() methods are essentially the same.</p> <pre><code>DocumentsDBEntities db = new DocumentsDBEntities(); public IQueryable&lt;Project&gt; FindAllProjects() { return db.Projects; } public IQueryable&lt;City&gt; FindAllCities() { return db.Cities; } public IQueryable&lt;Department&gt; FindAllDepartments() { return db.Departments; } </code></pre> <p>As mentioned before, Department fetching works; Project fetching causes the exception.</p> <p><strong>Edit 3:</strong></p> <p>I fixed it! The problem was with using the datatype of 'Text' in the Project table. If I changed the datatype from that column from 'Text' to 'String' it works flawlessly. Can anyone tell me why? </p>
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    1. COThanks for the stack trace. You mentioned the inner exception, can you provide the stack trace for that?
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    2. COIn the part that works you add just a string (project.Name)? In the one that doesn't work (if I can understand the question correctly), it appears the data-source is wired up to a list of objects and the error sounds like it is failing in retrieving suitable values for said objects. I believe the observed behavior may be a red-herring. Happy coding.
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    3. COIf I just use this line I still have the error fire: var x = projectRepo.FindAllProjects().Where(l => l.IDCity == idCity).ToList();
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