The result of a query cannot be enumerated more than once

Question

I am using the entity framework (ef) and am getting the following error:

"The result of a query cannot be enumerated more than once.".

I have a repository class which contains the ef data context. I then have a controller class (not to be confused with MVC controllers) which contains an instance of the repository. So far so good... I have a search method on the controller which is supposed to return an array of RadComboBoxItemData, which is used to populate a Telerik RadComboBox control.

public RadComboBoxItemData[] Search(int id, string searchText)
{
    var query = context.Search(id, searchText);
    List<RadComboBoxItemData> result = new List<RadComboBoxItemData>();
    foreach (var item in query)
    {
        RadComboBoxItemData itemData = new RadComboBoxItemData();
        itemData.Text = ""; // assign some text here..;
        itemData.Value = ""; /*assign some value here..*/
        result.Add(itemData);
    }

    return result.ToArray();
}

When I debug my code, I can get into the foreach loop, but then I get an error saying:

An exception of type 'System.InvalidOperationException' occurred in System.Data.Entity.dll but was not handled in user code

Additional information: The result of a query cannot be enumerated more than once.

My entity uses a function import of an existing stored proc.

// EF repository method calling the function imported method on the data context.
public IEnumerable<SearchItem> Search(int id, string searchText)
{
    return this.entityContext.Search(id, searchText);
}

The function import Search calls a stored precedure to return a collection of SearchItem.

I have a feeling that the foreach loop can't iterate because of something with the ef.

Answer 1

Try explicitly enumerating the results by calling ToList().

Change

foreach (var item in query)

to

foreach (var item in query.ToList())

Answer 2

Try replacing this

var query = context.Search(id, searchText);

with

var query = context.Search(id, searchText).tolist();

and everything will work well.