Question

private string? typeOfContract {   get { return (string?)ViewState['typeOfContract']; }   set { ViewState['typeOfContract'] = value; } } 

Later in the code I use it like this:

typeOfContract = Request.QueryString['type']; 

I am getting the following error at the declaration of typeOfContract line stating:

The type ‘string’ must be a non-nullable value type in order to use it as parameter ‘T’ in the generic type or method ‘System.Nullable<T>’

Any ideas? Basically, I want to make sure that 'type' exists in the QueryString before performing an action.

Answer 1

System.String is a reference type and already ‘nullable’.

Nullable<T> and the ? suffix are for value types such as Int32, Double, DateTime, etc.