Given the following line of code:
cmd.Parameters.Add(new SqlParameter("@displayId", SqlDbType.NVarChar).Value = customer.DisplayID);
I receive the following error: The SqlParameterCollection only accepts non-null SqlParameter type objects, not String objects.
However, rewriting it to use object intialization:
cmd.Parameters.Add(new SqlParameter("@displayId", SqlDbType.NVarChar) { Value = customer.DisplayID });
works just fine. Any pointer on why this is occuring?
The problem is a misplaced closing parenthesis:
cmd.Parameters.Add(new SqlParameter("@displayId", SqlDbType.NVarChar)).Value = customer.DisplayId;
Note that there are 2 closing parentheses before .Value. As you originally entered it, you are doing cmd.Parameters.Add(...); where the ... is
new SqlParameter("@displayId", SqlDbType.NVarChar).Value = customer.DisplayId
and that evaluates to customer.DisplayId, hence the message about it not accepting string types.
Also, you can add the parameter more succinctly with
cmd.Parameters.AddWithValue("@displayId", customer.DisplayId);
As to why new SqlParameter("@displayId", SqlDbType.NVarChar).Value = customer.DisplayId returns customer.DisplayId, consider that the assignment operator returns the value being assigned as its result, and in this case that would be customer.DisplayId. This is why you can assign a value to several variables at once:
int i, j, k;
i = j = k = 42;
cmd.Parameters.Add(new SqlParameter("@displayId", SqlDbType.NVarChar).Value = customer.DisplayID);
is the same as
var customerDisplayId = customer.DisplayID;
new SqlParameter("@displayId", SqlDbType.NVarChar).Value = customerDisplayId;
cmd.Parameters.Add(customerDisplayId);
now do you see why the compiler is complaining?
