Searching a column in Entity Framework with multiple values - entity-framework

Question

I am trying to run a search on one particular field of a table with a list of values. Not able to find a solution so far. Any help is really appreciated.
Here is the scenario
var records = new PagedList<Required>();
var result = db.Required.Where(x => filter == null || (x.Title.Contains(filter)) || x.CID.Contains(filter));
foreach (string str in SelectedNetwork)
{
string tempStr = str;
result = result.Where(x => x.Network == tempStr);
records.TotalRecords = result.Count();
}
records.Content = result
.Where(x => filter == null ||
(x.Title.Contains(filter))
|| x.CID.Contains(filter)
)
.OrderBy(sort + " " + sortdir)
.Skip((page - 1) * Convert.ToInt32(records.PageSize))
.Take(Convert.ToInt32(records.PageSize))
.ToList();
highlighted code in the foreach loop fails to run as per expectation. Is there any way, I can fix it?
Thanks
Tutumon

Answer 1

You must take into account that LINQ expressions are queries, until you materialize them. To materialize them you need to either enumerate them, or convert them to a list, array, or whatever, i.e. enumerate their members in a foreach, or call a method like ToList(), or ToArray().
In your code the original query stored in result is not materialized, so everytime a foreach loop is executed, a new Where contidion is added to the original query. To vaoid this behavior you need to recreate the whole results query in each iteration, so that you get a fresh copy of the unfilterd expression.
There would be another solution which would be to materialize the result query and then run the foreach loop as is. The problem of this solution would be that you would get all the data from the database, keep it in memory and run the Where and the Count on the in-memory copy. Unless there is a very small number of rows in Required that would be a very bad idea.