LINQ : The query results cannot be enumerated more than once [duplicate]

Question

This is my code

 searchDataContext db = new searchDataContext();

    var query = (from p in db.SearchFirst(city, area)
                select new
                {
                    ID = p.Id,
                    Address = p.address,
                    Level = p.agahilevel

                });
    int count =query.Count();

    // records
    var q = query.Skip(Convert.ToInt32(start)).Take(Convert.ToInt32(width));

    if (q.Count() > 0)
    {
        int index = 0;
        str += "[";
        foreach (var row in q)
        {
            if (index == 0)

I have an error in this code

The query results cannot be enumerated more than once.

please check that and answer me.

Answer 1

You cannot use cached queries and iterate over them more than once...
Make a List<T> of it and try it again

var q = query.ToList(); // work on this

Answer 2

Materialize your query:

var addresses = (from p in db.SearchFirst(city, area)
                select new
                {
                    ID = p.Id,
                    Address = p.address,
                    Level = p.agahilevel

                })
                .Skip(Convert.ToInt32(start))
                .Take(Convert.ToInt32(width))
                .ToList();

Then use Enumerable.Any to check if it contains elements:

if(addresses.Any())
{
    int index = 0; // ...
}

Answer 3

If you add .ToList() to your query your problem will be solved