Linq Query keeps throwing "Unable to create a constant value of type System.Object....", Why?

Question

The following is the code sample:

private void loadCustomer(int custIdToQuery)      {         var dbContext = new SampleDB();         try         {             var customerContext = from t in dbContext.tblCustomers      // keeps throwing:                                    where t.CustID.Equals(custIdToQuery) // Unable to create a constant value of type 'System.Object'.                                     select new                           // Only primitive types ('such as Int32, String, and Guid')                                     {                                    // are supported in this context.                                        branchId = t.CustomerBranchID,   //                                        branchName = t.BranchName        //                                    };                                   //              if (customerContext.ToList().Count() < 1) //Already Tried customerContext.Any()             {                 lstbCustomers.DataSource = customerContext;                 lstbCustomers.DisplayMember = "branchName";                 lstbCustomers.ValueMember = "branchId";             }             else             {                 lstbCustomers.Items.Add("There are no branches defined for the selected customer.");                 lstbCustomers.Refresh();             }         }         catch (Exception ex)         {             MessageBox.Show(ex.Message);         }         finally         {             dbContext.Dispose();         }     } 

i am unable to understand what am i doing wrong. I keep getting "Unable to create a constant value of type 'System.Object'. Only primitive types ('such as Int32, String, and Guid') are supported in this context."

Answer 1

Use == instead of Equals:

where t.CustID == custIdToQuery 

If the types are incorrect you may find that this doesn't compile.

Answer 2

I had the same issue with a nullable int. Using == instead works nicely, but if you want to use .Equals, you can compare it to the value of the nullable variable, so

where t.CustID.Value.Equals(custIdToQuery)