105 lines
2.7 KiB
Plaintext
105 lines
2.7 KiB
Plaintext
Methods declared as `public`, `protected`, or `protected internal` can be accessed from other assemblies, which means you should validate parameters to be within the expected constraints. In general, checking against `null` 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 `null` before being dereferenced.
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== Noncompliant Code Example
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[source,csharp]
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----
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public class MyClass
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{
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private MyOtherClass other;
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public void Foo(MyOtherClass other)
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{
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this.other = other.Clone(); // Noncompliant
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}
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protected void Bar(MyOtherClass other)
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{
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this.other = other.Clone(); // Noncompliant
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}
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}
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----
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== Compliant Solution
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[source,csharp]
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----
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public class MyClass
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{
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private MyOtherClass other;
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public void Foo(MyOtherClass other)
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{
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if (other != null)
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{
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this.other = other.Clone();
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}
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}
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protected void Bar(MyOtherClass other)
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{
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if (other != null)
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{
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this.other = other.Clone();
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}
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}
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public void Baz(MyOtherClass other)
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{
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ArgumentNullException.ThrowIfNull(other);
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this.other = other.Clone();
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}
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public void Qux(MyOtherClass other)
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{
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this.other = other; // Compliant: "other" is not being dereferenced
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}
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private void Xyzzy(MyOtherClass other)
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{
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this.other = other.Clone(); // Compliant: method is not publicly accessible
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}
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}
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----
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== Exceptions
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* Arguments validated for `null` 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,csharp]
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----
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using System;
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[AttributeUsage(AttributeTargets.Parameter, Inherited=false)]
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public sealed class ValidatedNotNullAttribute : Attribute { }
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public static class Guard
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{
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public static void NotNull<T>([ValidatedNotNullAttribute] T value, [CallerArgumentExpression("value")] string name = "") where T : class
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{
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if (value == null)
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throw new ArgumentNullException(name);
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}
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}
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public static class Utils
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{
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public static string ToUpper(string value)
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{
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Guard.NotNull(value);
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return value.ToUpper(); // Compliant
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}
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}
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----
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include::../rspecator.adoc[] |