update data using viewmodel
<p>I'm trying to update dataEntry using viewmodel and I'm getting this error msg :</p>

<blockquote>
  <p>Store update, insert, or delete statement affected an unexpected
  number of rows (0). Entities may have been modified or deleted since
  entities were loaded.</p>
</blockquote>

<p>As far as I understand it's showing the ID is missing , but onDebug I can c the foreign id (<code>model.rgrade.SubjectId</code>) I cant finger out how to find the model rgradeId(   in the results.</p>

<p>This is my code :</p>

<pre><code>//checked if the subject name is allready in the db
var subjectNameQuery = db.Subject.Where(n =&gt; n.SubjectName.ToLower().Equals(model.sub.SubjectName));
if (subjectNameQuery.Count() &gt; 0)
{
    //if the name is in the table, do Not add the name of the Id again
    model.rev.SubjectId = subjectNameQuery.SingleOrDefault().SubjectId;
    model.rgrade.SubjectId = subjectNameQuery.SingleOrDefault().SubjectId;
    if (model.rev.GBU == "Good")
    {
        model.rgrade.Good = +1;
    }
    else if (model.rev.GBU == "Bad")
    {
        model.rgrade.bad = +1;
    }
    else if (model.rev.GBU == "Ugly")
    {
        model.rgrade.Ugly = +1;
    }

    db.Entry(model.rgrade).State = EntityState.Modified;
}
</code></pre>