85 lines
2.6 KiB
Plaintext
85 lines
2.6 KiB
Plaintext
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Methods declared as `Public`, `Protected`, or `Protected Friend` can be accessed from other assemblies, which means you should validate parameters to be within the expected constraints. In general, checking against `Nothing` is recommended in defensive programming.
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This rule raises an issue when a parameter of a publicly accessible method is not validated against `Nothing` before being dereferenced.
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== Noncompliant Code Example
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[source,vbnet]
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----
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Public Class Sample
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Public Property Message As String
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Public Sub PublicMethod(Arg As Exception)
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Message = Arg.Message ' Noncompliant
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End Sub
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Protected Sub ProtectedMethod(Arg As Exception)
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Message = Arg.Message ' Noncompliant
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End Sub
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End Class
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----
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== Compliant Solution
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[source,vbnet]
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----
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Public Class Sample
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Public Property Message As String
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Public Sub PublicMethod(Arg As Exception)
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If Arg IsNot Nothing Then Message = Arg.Message ' Noncompliant
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End Sub
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Protected Sub ProtectedMethod(Arg As Exception)
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ArgumentNullException.ThrowIfNull(Arg)
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Message = Arg.Message ' Noncompliant
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End Sub
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Private Sub PrivateMethod(Arg As Exception)
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Message = Arg.Message ' Compliant: method is not publicly accessible
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End Sub
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End Class
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----
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== Exceptions
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* Arguments validated for `Nothing` via helper methods should be annotated with the https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/attributes/nullable-analysis#postconditions-maybenull-and-notnull[`[NotNull]`] attribute.
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* Method parameters marked with the `[NotNull]` https://www.jetbrains.com/help/resharper/Reference__Code_Annotation_Attributes.html#ItemNotNullAttribute[Resharper code annotation attribute] are supported as well.
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* To create a custom null validation method declare an attribute with name `ValidatedNotNullAttribute` and mark the parameter that is validated for null in your method declaration with it:
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[source,vbnet]
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----
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Imports System.Runtime.CompilerServices
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<AttributeUsage(AttributeTargets.Parameter, Inherited:=False)>
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Public NotInheritable Class ValidatedNotNullAttribute
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Inherits Attribute
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End Class
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Public Module Guard
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Public Sub NotNull(Of T As Class)(<ValidatedNotNullAttribute> Value As T, <CallerArgumentExpression("Value")> Optional Name As String = "")
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If Value Is Nothing Then Throw New ArgumentNullException(Name)
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End Sub
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End Module
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Public Module SampleUsage
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Public Function CustomToUpper(Value As String) As String
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Guard.NotNull(Value)
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Return Value.ToUpper
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End Function
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End Module
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----
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include::../rspecator.adoc[]
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