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copied!<pre><code>public int GetPage(int orderId, int sampleId, int itemsPerPage) { //protect against divide by zero if(itemsPerPage < 1) return 1;//or 0 if you want page index int index = _context.Set<Sample>() .Where(s => s.OrderId == orderId && s.Id < sampleId) //.OrderBy(s => s.Id) edited after accepted OrderBy not necessary .Count(); //if index is zero return 1 //if index == 9 and itemsPerPage == 10 return 1 //if index == 10 and itemsPerPage == 10 return 2 //if you want the page index rather than the page number don't add 1 return 1 + (index / itemsPerPage); } </code></pre> <p>@Rob Lyndon's effort made me think some more, and I came up with this as a way of checking that the page actually contains the sample - in one query to the database </p> <pre><code>public int GetPage(int orderId, int sampleId, int itemsPerPage) { //protect against divide by zero if(itemsPerPage < 1) return 1;//or 0 if you want page index, or -1 if you want to flag this as invalid var result = context.Set<Sample>() .Where(s => s.OrderId == orderId && s.Id <= sampleId)//this time include sampleId //.OrderBy(s => s.ID) edited after accepted OrderBy not necessary .GroupBy(x => true) .Select(group => new { MaxID = group.Max(s => s.Id), Count = group.Count() }) .Single(); //Check the sample is actually in the result if(result.MaxID != sampleId) return 1;//or 0 if you want page index, or -1 if you want to flag this as invalid int index = result.Count - 1; //if you want the page index rather than the page number don't add 1 return 1 + (index / itemsPerPage); } </code></pre>

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