Question

Please look at the code:

// get column list from entity framework
var listID = from Ines in ineContext.IneDetailRecords
             select Ines.InePIN.ToString().ToList();
string PIN = something;
if(!listID.Contains(PIN))
    // save it to DB

InePIN is a cloumn in SQL Server DB, the type is varchar(20).

The exception is:

Instance argument: cannot convert from 'System.Linq.IQueryable<System.Collections.Generic.List<char>>' to 'System.Linq.ParallelQuery<string>'

Answer 1

You need to apply the ToList method on result of query but not on the selected column i.e Ines.InePIN.ToString().ToList()

Change

var listID = from Ines in ineContext.IneDetailRecords
                                       select Ines.InePIN.ToString().ToList();

To

var listID = (from Ines in ineContext.IneDetailRecords
                                       select Ines.InePIN.ToString()).ToList();