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POLinq "join" with a IList<T> getting "Error Unable to create a constant value.."
 

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  1. POLinq "join" with a IList<T> getting "Error Unable to create a constant value.."
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    <p>I have a Save Method that saves with a Linq query a <em>manually re-orderd list</em> (in a web form) that is <em>passed as the parameter to my method</em>, and I try to update the <strong>Order Property</strong> of the <code>IEnumerable&lt;VM_CategoryLabel&gt;</code> I retrieve from the database (EF) with the corresponding value in the list (maybe would that be clearer with my code below):</p> <pre><code>public static void SaveFromList(IList&lt;VM_CategoryLabelExtra&gt; listTemplate) { int idCat = listTemplate.Select(x =&gt; x.IdCat).FirstOrDefault(); var test = (int)listTemplate.Where(z =&gt; z.Id == 8).Select(z =&gt; z.Order).FirstOrDefault(); using (var context = new my_Entities()) { var requete = from x in context.arc_CatLabel where x.ID_Categorie == idCat orderby x.Sequence_Cat select new VM_CategoryLabel { Id = x.ID_LabelPerso, //Order = x.Sequence_Cat, Order = (int)listTemplate.Where(z =&gt; z.Id == x.ID_LabelPerso).Select(z =&gt; z.Order).First(), Label = x.arc_Label.Label, Unit = x.arc_Label.Unit }; context.SaveChanges(); } } </code></pre> <p>I used the <em>"test" var</em> to see if my "sub-query" gets the correct value, and it does, but when I use my Linq expression inside the Select (the commented Order line), I get the following error:</p> <p><strong>Unable to create a constant value of type 'Namespace.Models.VM_CategoryLabelExtra. "Only primitive types and enumeration types are supported in this context.</strong></p> <p>Here are my classes:</p> <pre><code> public class VM_CategoryLabel { public int Id { get; set; } public int Order { get; set; } public string Label { get; set; } public string Unit { get; set; } public bool Checked { get; set; } } public class VM_CategoryLabelExtra { public int Id { get; set; } public int IdCat { get; set; } public int Order { get; set; } public string Label { get; set; } public string Unit { get; set; } public bool Checked { get; set; } } </code></pre> <p>So I suppose that I should not query the list inside my query ? So how do I "match" the 2 lists of values ?</p> <p>I also tried the following (after having replace in the Linq query: Order = x.Sequence_Cat)that is not working neither because the iteration variable is read-only:</p> <pre><code>foreach (var item in requete) { item.Order = listTemplate.Where(x =&gt; x.Id == item.Id).Select(x =&gt; x.Order).FirstOrDefault(); } try { context.SaveChanges(); </code></pre>
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      1. POLinq "join" with a IList<T> getting "Error Unable to create a constant value.."
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    1. COI cant understant this "Order = (int)listTemplate.Where" and Order = x.Sequence_Cat? You cant use twice
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      1. USElvin Mammadov
    2. COwhen I uncomment the 2nd "Order" I comment the first one (that get the values actually in the database). So I only use 1 Order in my query :)
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    3. CO@Bro I like your avatar/picture. Is that really you?
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      1. USKing King
 

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