If a variable is dereferenced, for example as the qualifier in a method call, and the variable may have a null value on some execution paths leading to the dereferencing, the dereferencing may result in a NullReferenceException.

Ensure that the variable does not have a null value when it is dereferenced.

In the following example, the method DoPrint() dereferences its parameter o unconditionally, resulting in a NullReferenceException via the call DoPrint(null).

In the revised example, the method DoPrint() guards the dereferencing with a null check.

  • Microsoft, NullReferenceException Class.
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