Question

I’m trying to insert the data into my database which has 2 tables

Products
(ProductID): 1
(IDNumber) : 200900110
(ProductName) : Pepsi

Order
(OrderID): 1 (Auto Increment by 1)
(ProductID):1
(Date): 1/1/2009

The code is this:

var db = new ProductOrder(); var idNum = from p in db.Product             where p.IDNumber == 200900110              select p.ProductID;   var order = new Order();             order.productID = Convert.ToInt32(idNum);             order.Date = DateTime.Now; db.Order.InsertOnSubmit(nTime); db.SubmitChanges(); 

After I run it gives me the error like this:

Unable to cast object of type ‘System.Data.Linq.DataQuery`1[System.Int32]’ to type ‘System.IConvertible’

Answer 1

Your query:

from p in db.Product where p.IDNumber == 200900110 select p.ProductID 

does not return a single result but a list of results. In your case this will be a list containing a single product id. You should modify it to this:

(from p in db.Product  where p.IDNumber == 200900110  select p.ProductID).Single() 

If you run your code in the debugger and you hover your mouse over the idNum variable, you’ll see that it is a DataQuery instance.