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POEntity Framework: Avoiding Inserting Duplicates
 

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    <p>Say, I have the following conceptual model, there are strories that have tags (more than one, so it's a many-to-many relationship), plus each tag belongs to a particular category.</p> <p>My data comes from an external source and before inserting it I want to make sure that no duplicated tags are added.</p> <p><strong>Updated code snippet:</strong></p> <pre><code>static void Main(string[] args) { Story story1 = new Story(); story1.Title = "Introducing the Entity Framework"; story1.Tags.Add(new Tag { Name = ".net", }); story1.Tags.Add(new Tag { Name = "database" }); Story story2 = new Story(); story2.Title = "Working with Managed DirectX"; story2.Tags.Add(new Tag { Name = ".net" }); story2.Tags.Add(new Tag { Name = "graphics" }); List&lt;Story&gt; stories = new List&lt;Story&gt;(); stories.Add(story1); stories.Add(story2); EfQuestionEntities db = new EfQuestionEntities(); Category category = (from c in db.Categories where c.Name == "Programming" select c).First(); foreach (Story story in stories) { foreach (Tag tag in story.Tags) { Tag currentTag = tag; currentTag = GetTag(tag.Name, category, db); } db.Stories.AddObject(story); } db.SaveChanges(); } public static Tag GetTag(string name, Category category, EfQuestionEntities db) { var dbTag = from t in db.Tags.Include("Category") where t.Name == name select t; if (dbTag.Count() &gt; 0) { return dbTag.First(); } var cachedTag = db.ObjectStateManager.GetObjectStateEntries(EntityState.Added). Where(ose =&gt; ose.EntitySet == db.Tags.EntitySet). Select(ose =&gt; ose.Entity). Cast&lt;Tag&gt;().Where(x =&gt; x.Name == name); if (cachedTag.Count() != 0) { return cachedTag.First(); } Tag tag = new Tag(); tag.Name = name; tag.Category = category; db.Tags.AddObject(tag); return tag; } </code></pre> <p>However, I get an exception about an object with the same EntityKey that is already present in the ObjectContext.</p> <p>Also, if I remove the else statement I will get an exception about violating an FK constraint, so it seems like its Category attribute is set to null.</p>
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