.NET Tips | آرشیو گروه‌های اشتراک‌های NullReferenceExceptions، صفحه: 1

Check	Code	Description
Is Null	if(variable is null) return true;	This syntax supports static analysis such that later code will know whether variable is null or not. Doesn’t produce a warning even when comparing against a non-nullable value type making the code to check pointless. Requires C# 7.0 because it leverages type pattern matching.
Is Not Null	if(variable is { }) return false	This syntax supports static analysis such that later code will know whether variable is null or not. Requires C# 8.0 since this is the method for checking for not null using property pattern matching.
Is Not Null	if(variable is object) return false	Triggers a warning when comparing a non-nullable value type which could never be null This syntax works with C# 8.0’s static analysis so later code will know that variable has been checked for null. Checks if the value not null by testing whether it is of type object. (Relies on the fact that null values are not of type object.)
Is Null	if(variable == null) return true	The only way to check for null prior to C# 7.0. However, because the equality operator can be overridden, this has the (remote) possibility of failing or introducing a performance issue.
Is Not Null	if(variable != null) return false	The only way to check for not null prior to C# 7.0. Since the not-equal operator can be overridden, this has the (remote) possibility of failing or introducing a performance issue.