LINQ to Entities Error

Emmmanuel FIADUFE

Hello Team,

Please am having this error, kindly assist.

Additional information: LINQ to Entities does not recognize the method 'System.String ToString()' method, and this method cannot be translated into a store expression.

public ActionResult Room()
{
RoomViewModel objRoomViewModel = new RoomViewModel();

List bookingStatusList = objHotelDbEntities.BookingStatus
.Select(obj => new SelectListItem()
{
Text = obj.BookingStatus,
Value = Convert.ToInt32(obj.BookingStatusId).ToString(),
Selected = false
}).ToList();
List roomTypeList = objHotelDbEntities.RoomTypes
.Select(obj => new SelectListItem()
{
Text = obj.RoomTypeName,
Value = Convert.ToInt32(obj.RoomTypeId).ToString(),
Selected = false
}).ToList();
objRoomViewModel.ListOfBookingStatus = bookingStatusList;
objRoomViewModel.ListOfRoomRtype = roomTypeList;
return View(objRoomViewModel);

}

4 Replies

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Prasad Raveendran3y ago

Accepted answer

The error you're encountering, "LINQ to Entities does not recognize the method 'System.String ToString()'", occurs because LINQ to Entities doesn't support the ToString method within a query. In your code, you're trying to convert the obj.BookingStatusId and obj.RoomTypeId to strings within the LINQ query, and this is not allowed.

To fix this issue, you should first retrieve the data from the database using LINQ to Entities and then perform the conversion to string outside of the LINQ query. Here's how you can modify your code:

public ActionResult Room()
{
    RoomViewModel objRoomViewModel = new RoomViewModel();

    List bookingStatusList = objHotelDbEntities.BookingStatus
        .AsEnumerable() // Switch to LINQ to Objects
        .Select(obj => new SelectListItem()
        {
            Text = obj.BookingStatus,
            Value = obj.BookingStatusId.ToString(), // Convert to string outside LINQ to Entities
            Selected = false
        }).ToList();

    List roomTypeList = objHotelDbEntities.RoomTypes
        .AsEnumerable() // Switch to LINQ to Objects
        .Select(obj => new SelectListItem()
        {
            Text = obj.RoomTypeName,
            Value = obj.RoomTypeId.ToString(), // Convert to string outside LINQ to Entities
            Selected = false
        }).ToList();

    objRoomViewModel.ListOfBookingStatus = bookingStatusList;
    objRoomViewModel.ListOfRoomRtype = roomTypeList;
    return View(objRoomViewModel);
}

By calling AsEnumerable() before the Select statement, you switch from LINQ to Entities to LINQ to Objects, allowing you to use the ToString() method for conversion without causing the error.

Saravanan Ganesan2y ago
The error you're encountering, "LINQ to Entities does not recognize the method 'System.String ToString()'," occurs because you're trying to execute a ToString() method inside a LINQ to Entities query. LINQ to Entities translates queries into SQL, and some operations, like ToString(), can't be translated directly.

To fix this, you should materialize the query by calling .ToList() before using ToString(). For example:

Value = obj.BookingStatusId.ToString()
This way, the query results will be retrieved from the database, and then you can apply ToString() without causing an error. Repeat this pattern for any other methods or conversions that can't be translated into SQL.

Amit Mohanty3y ago

public ActionResult Room()
{
    RoomViewModel objRoomViewModel = new RoomViewModel();

    List bookingStatusList = objHotelDbEntities.BookingStatus
        .ToList()
        .Select(obj => new SelectListItem()
        {
            Text = obj.BookingStatus,
            Value = obj.BookingStatusId.ToString(),
            Selected = false
        }).ToList();

    List roomTypeList = objHotelDbEntities.RoomTypes
        .ToList() 
        .Select(obj => new SelectListItem()
        {
            Text = obj.RoomTypeName,
            Value = obj.RoomTypeId.ToString(),
            Selected = false
        }).ToList();

    objRoomViewModel.ListOfBookingStatus = bookingStatusList;
    objRoomViewModel.ListOfRoomRtype = roomTypeList;
    
    return View(objRoomViewModel);
}

Mohammad Hussain3y ago

public ActionResult Room()
{
    RoomViewModel objRoomViewModel = new RoomViewModel();

    // Fetch the data from the database first
    List bookingStatusList = objHotelDbEntities.BookingStatus.ToList();
    List roomTypeList = objHotelDbEntities.RoomTypes.ToList();

    // Then, create SelectListItem objects in memory
    List bookingStatusSelectList = bookingStatusList
        .Select(obj => new SelectListItem()
        {
            Text = obj.BookingStatus,
            Value = obj.BookingStatusId.ToString(),
            Selected = false
        }).ToList();

    List roomTypeSelectList = roomTypeList
        .Select(obj => new SelectListItem()
        {
            Text = obj.RoomTypeName,
            Value = obj.RoomTypeId.ToString(),
            Selected = false
        }).ToList();

    objRoomViewModel.ListOfBookingStatus = bookingStatusSelectList;
    objRoomViewModel.ListOfRoomRtype = roomTypeSelectList;

    return View(objRoomViewModel);
}