Why is this an issue?
When constraints have not been applied to restrict a generic type parameter to be a reference type, then a value type, such as a
struct
, could also be passed. In such cases, comparing the type parameter to null
would always be false, because a
struct
can be empty, but never null
. If a value type is truly what’s expected, then the comparison should use
default()
. If it’s not, then constraints should be added so that no value type can be passed.
Noncompliant code example
private bool IsDefault<T>(T value)
{
if (value == null) // Noncompliant
{
// ...
}
// ...
}
Compliant solution
private bool IsDefault<T>(T value)
{
if(object.Equals(value, default(T)))
{
// ...
}
// ...
}
or
private bool IsDefault<T>(T value) where T : class
{
if (value == null)
{
// ...
}
// ...
}