error while querying sql through linq

Question

User81789783 posted

i m facing below error

Error    7    Cannot implicitly convert type 'System.Linq.IQueryable<CallCenterCRM.TBL_Department>' to 'System.Collections.Generic.List<CallCenterCRM.Models.TBL_Department>'. An explicit conversion exists (are you missing a cast?)    C:\Users\erum\Documents\Visual Studio 2012\Projects\CallCenterCRM\CallCenterCRM\Models\TBL_Department.cs    134    29    CallCenterCRM
i have below code

  public static List<TBL_Department> GetDeptbyprefix(string prefix)
        {
            CallCenterDboDataContext obj = new CallCenterDboDataContext("Data Source=erum-pc;Initial Catalog=CallCenter;User ID=sa;Password=sa;");


            List<TBL_Department> DeptList = new List<TBL_Department>();

            //DeptList = from dept in obj.TBL_Departments
            //            where dept.prefix == prefix
            //            select dept;

            using (CallCenterDboDataContext dbcontext = new CallCenterDboDataContext())
            {
                DeptList = from dept in dbcontext.TBL_Departments
                            where dept.prefix == prefix
                            select dept;
            }

            return DeptList;

        }

Answer 1

User1120430333 posted

DeptList = (from dept in dbcontext.TBL_Departments where dept.prefix == prefix select dept).ToList();

https://msdn.microsoft.com/en-us/library/bb342261%28v=vs.110%29.aspx?f=255&MSPPError=-2147217396

Creates a List<T> from an IEnumerable<T>.

https://msdn.microsoft.com/en-us/library/bb351562(v=vs.110).aspx

This interface inherits the IEnumerable<T> interface so that if it represents a query, the results of that query can be enumerated. Enumeration forces the expression tree associated with an IQueryable<T> object to be executed. Queries that do not return enumerable results are executed when the Execute<TResult>(Expression) method is called.

Answer 2

User991499041 posted

Hi Erum,

If you read the error message. It's telling you EXACTLY what's wrong. 

To convert IQuerable to a list, you can do the following:

var q = from dept in dbcontext.TBL_Departments
        where dept.prefix == prefix
        select dept;

DeptList = q.ToList();

Regards,

zxj

Answer 3

User81789783 posted

well zxj i changed code as per ur suggestion but same issue ,but one error this time

Error    7    Cannot implicitly convert type 'System.Collections.Generic.List<CallCenterCRM.TBL_Department>' to 'System.Collections.Generic.List<CallCenterCRM.Models.TBL_Department>'    C:\Users\erum\Documents\Visual Studio 2012\Projects\CallCenterCRM\CallCenterCRM\Models\TBL_Department.cs    141    24    CallCenterCRM

     public static List<TBL_Department> GetDeptbyprefix(string prefix)
        {
            CallCenterDboDataContext obj = new CallCenterDboDataContext("Data Source=erum-pc;Initial Catalog=CallCenter;User ID=sa;Password=sa;");


            List<TBL_Department> DeptList = new List<TBL_Department>();

            //DeptList = from dept in obj.TBL_Departments
            //            where dept.prefix == prefix
            //            select dept;

            var q = from dept in obj.TBL_Departments
                    where dept.prefix == prefix
                    select dept;

            DeptList = q.ToList();

            return DeptList;

        }
    

Answer 4

User81789783 posted

DA924 ,ur lines of code is not working at all ,

Answer 5

User1120430333 posted

Error    7    Cannot implicitly convert type 'System.Collections.Generic.List<CallCenterCRM.TBL_Department>' to 'System.Collections.Generic.List<CallCenterCRM.Models.TBL_Department>'    C:\Users\erum\Documents\Visual Studio 2012\Projects\CallCenterCRM\CallCenterCRM\Models\TBL_Department.cs    141    24    CallCenterCRM

You can't do it because you can't cast an object across to different namespace even if its the  same object.

CallCenterCRM.Models.TBL_Department vs CallCenterCRM.TBL_Department are two objects that may be the same object but they are not as  .NET sees it.

http://csharp-station.com/Tutorial/Linq/Lesson02

Listing 2-5: Custom Projection with Data Source Type

TBL_Department is the projected object you  will make using the  custom projection lorded into your  List<TBL_Department>

And put the ().Tolist() around the code as you were shown.