Class NotNull

A validation rule which passes if the value being validated is not null and fails if it is.

Inheritance
System.Object
NotNull
Implements
IRuleWithMessage<System.Object>
IRule<System.Object>
IGetsFailureMessage<System.Object>
Inherited Members
System.Object.Equals(System.Object)
System.Object.Equals(System.Object, System.Object)
System.Object.GetHashCode()
System.Object.GetType()
System.Object.MemberwiseClone()
System.Object.ReferenceEquals(System.Object, System.Object)
System.Object.ToString()
Namespace: CSF.Validation.Rules
Assembly: CSF.Validation.StandardRules.dll
Syntax
public class NotNull : IRuleWithMessage<object>, IRule<object>, IGetsFailureMessage<object>
Remarks

This rule uses the validated value's default equality comparer to test whether it is equal to null or not. If the validated value is of a type which has an overridden System.Object.Equals(System.Object) method, that method will be used.

Note that it is good practice for all rules which operate upon nullable values to pass if they are null. Because of this, it is common to apply this rule to all nullable values which are mandatory. Read more at this best-practices article.

This rule will always return a synchronous result.

Methods

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GetFailureMessageAsync(Object, ValidationRuleResult, CancellationToken)

Gets the validation failure message for the specified result.

Declaration
public ValueTask<string> GetFailureMessageAsync(object value, ValidationRuleResult result, CancellationToken token = default(CancellationToken))
Parameters
Type Name Description
System.Object value
ValidationRuleResult result

A validation result, typically indicating failure.
System.Threading.CancellationToken token

An optional cancellation token.
Returns
Type Description
System.Threading.Tasks.ValueTask<System.String>

A human-readable message.
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GetResultAsync(Object, RuleContext, CancellationToken)

Performs the validation logic asynchronously and returns a task of RuleResult.

Declaration
public ValueTask<RuleResult> GetResultAsync(object validated, RuleContext context, CancellationToken token = default(CancellationToken))
Parameters
Type Name Description
System.Object validated
RuleContext context

Contextual information about the validation
System.Threading.CancellationToken token

An object which may be used to cancel the process
Returns
Type Description
System.Threading.Tasks.ValueTask<RuleResult>

A task which provides a result object, indicating the result of validation
Remarks

This method receives the value to be validated as well as an object which represents the context in which this rule is running. It should return a task of RuleResult.

In order to create the result object, particularly if your rule logic will run synchronously, consider using the CommonResults class via using static CSF.Validation.Rules.CommonResults; in your rule logic. The common results class has helper methods such as PassAsync(IDictionary<String, Object>) and FailAsync(IDictionary<String, Object>) which include optimisations for flyweight task instances that avoid allocating additional resources needlessly.

It is acceptable to throw an uncaught exception from this method, as the validation framework will catch it and automatically convert it into an error result. Generally, developers do not need to manually return a result of outcome Errored manually. This would be appropriate only in an unusual scenario that is considered an error, but which does not involve the throwing of an exception. Error results are generally harder for the consumer to deal with than failure results.

The context parameter may be used, amongst other things, to access 'ancestor' values. However, if this rule only needs access to an immediate parent value then consider using IRule<TValue, TParent> instead.

Exceptions
Type Condition
System.Exception

This method may raise any exception type

Implements