Is it possible to pass a parameter that is DB.null and set a value in the database equal to that?

Question

I'm pulling data from a database (1 record) and putting each value in a textbox or dropdownlist. Some of these values are DB.null. If they are, I convert each of them to "" (blank). However, once the user has modified the textboxes/dropdown list, they can "Save" the new results. My problem is this:

If the user leaves something blank, I want to be able to maintain that the value is DB.null. Is there a way to do this?

Also, is it possible that if there is a value in a textbox and the user decides to delete it, I can also convert it to DB.Null? Here's what I tried to do to give you guys some idea:

productName != ""
    ? myCommand.Parameters.AddWithValue("@ProductName", productName)
    : myCommand.Parameters.AddWithValue("@ProductName", DBNull.Value);

Answer 1

With SQL Server I believe you can interchangably use null or DBNull.Value to set a value to NULL.

I'd also change your code to this:

myCommand.Parameters.AddWithValue(
    "@ProductName",
    // this requires a cast as ?: must return the same type
    String.IsNullOrWhiteSpace(productName)
        ? (object)DBNull.Value
        : (object)productName
);

Or using null and without an explicit cast:

myCommand.Parameters.AddWithValue(
    "@ProductName",
    ! String.IsNullOrWhiteSpace(productName) ? productName : null
);