ValidatingObjectBase Class

Represents an object with validating capabilities by adding IValidatingObject implementation to the PersistableObjectBase class.

Definition

Namespace: KGySoft.ComponentModel
Assembly: KGySoft.CoreLibraries (in KGySoft.CoreLibraries.dll) Version: 9.0.0-preview.1

C#

[SerializableAttribute]
public abstract class ValidatingObjectBase : PersistableObjectBase, 
	IValidatingObject, IDataErrorInfo

VB

<SerializableAttribute>
Public MustInherit Class ValidatingObjectBase
	Inherits PersistableObjectBase
	Implements IValidatingObject, IDataErrorInfo

C++

[SerializableAttribute]
public ref class ValidatingObjectBase abstract : public PersistableObjectBase, 
	IValidatingObject, IDataErrorInfo

F#

[<AbstractClassAttribute>]
[<SerializableAttribute>]
type ValidatingObjectBase = 
    class
        inherit PersistableObjectBase
        interface IValidatingObject
        interface IDataErrorInfo
    end

Inheritance: Object ObservableObjectBase PersistableObjectBase ValidatingObjectBase

Derived: KGySoft.ComponentModelModelBase

Implements: IValidatingObject, IDataErrorInfo

Remarks

In a derived class the DoValidation method must be overridden.

Validation is automatically performed when the IsValid or ValidationResults property is accessed or when the object is accessed by the standard IDataErrorInfo interface.

IsValid returns if ValidationResults does not contain any entries with Error severity.

Differences between CanGetProperty/CanSetProperty methods and IsValid/ValidationResults properties:

When CanGetProperty and CanSetProperty methods return , then an exception will be thrown when the property is get or set via the ObservableObjectBase and IPersistableObject members. Do not use these methods for business validation. Instead, they can be used to prevent accessing an unknown property or when a property is tried to be set by a value of invalid type.
On the other hand, IsValid and ValidationResults properties can be used to indicate whether an object contains problematic values. For every issue a severity level (see ValidationSeverity) and a corresponding message can be assigned. These can be displayed by a UI, for example.

IDataErrorInfo support:
ValidatingObjectBase implements also the System.ComponentModel.IDataErrorInfo interface, which is the oldest standard way in .NET to support validation, therefore it is supported by most frameworks. IDataErrorInfo is able to report errors only, so if warnings and validation infos should also be displayed by a UI, then the object should be accessed via the IValidatingObject interface.

Example

The following example shows how to implement property validation:

C#

public class MyModel : ValidatingObjectBase
{
    public int Id { get => Get<int>(); set => Set(value); }

    public string Name { get => Get<string>(); set => Set(value); }

    protected override ValidationResultsCollection DoValidation()
    {
        var result = new ValidationResultsCollection();

        // info
        if (Id == 0)
            result.AddInfo(nameof(Id), "This will be considered as a new object when saved");
            // or: result.Add(new ValidationResult(nameof(Id), "This will be considered as a new object when saved", ValidationSeverity.Information));

        // warning
        if (Id < 0)
            result.AddWarning(nameof(Id), $"{nameof(Id)} is recommended to be greater or equal to 0.");

        // error
        if (String.IsNullOrEmpty(Name))
            result.AddError(nameof(Name), $"{nameof(Name)} must not be null or empty.");

        return result;
    }
}

Notes to Implementers

For another example see the Remarks section of the ObservableObjectBase class. The same applies also for the ValidatingObjectBase class regarding the ways of defining properties in a derived class.

Constructors

ValidatingObjectBase

Initializes a new instance of the ValidatingObjectBase class

Properties

AllowReadingDisposedObject	Gets whether the Get<T> method (and the observable properties using it) throw an ObjectDisposedException when the IsDisposed property returns . In a derived class this property can be overridden to return , in which case the Get<T> method returns the default value of T after the object is disposed. The base implementation returns . (Inherited from ObservableObjectBase)
IsDisposed	Gets whether this instance has already been disposed. (Inherited from ObservableObjectBase)
IsModified	Gets whether this instance has been modified. Modified state can be set by the SetModified method. (Inherited from ObservableObjectBase)
IsValid	Gets whether this instance is valid. That is, if ValidationResults property does not return any entries where the value of Severity is Error.
ValidationResults	Gets the validation results for this instance.

Methods

AffectsModifiedState	Gets whether the change of the specified propertyName affects the IsModified property. The EditableObjectBase implementation excludes the IsModified, IsValid and ValidationResults properties. (Overrides ObservableObjectBaseAffectsModifiedState(String))
CanGetProperty	Gets whether the specified property can be retrieved. The base implementation allows to get the actual instance properties in this instance. (Inherited from ObservableObjectBase)
CanSetProperty	Gets whether the specified property can be set. The base implementation allows to set the actual instance properties in this instance if the specified value is compatible with the property type. (Inherited from ObservableObjectBase)
Clone	Creates a new object that is a copy of the current instance. The base implementation clones the internal property storage, the IsModified property and if clonePropertyChanged is , then also the subscribers of the PropertyChanged event. It respects the implementations with some special handling for arrays so arrays can be deep-cloned as well. (Inherited from ObservableObjectBase)
Dispose	Releases the resources held by this instance. (Inherited from ObservableObjectBase)
Dispose(Boolean)	Releases the resources held by this instance. The base implementation removes the subscribers of the PropertyChanged event and clears the property storage. If the overridden method disposes properties accessed by the Get<T> and Set methods, then check the IsDisposed property first and call the base method as the last step to prevent ObjectDisposedException. (Inherited from ObservableObjectBase)
DoValidation	Performs the validation on this instance and returns the validation results. Must not return .
GetT(FuncT, String)	Gets the value of a property, or - if it was not set before -, then creates its initial value. The created initial value will be stored in the internal property storage without triggering the PropertyChanged event. For constant or simple expressions, or to return a default value for a non-existing property without storing it internally use the other Get overload. For an example, see the Remarks section of the ObservableObjectBase class. (Inherited from ObservableObjectBase)
GetT(T, String)	Gets the value of a property or defaultValue if no value is stored for it. No new value will be stored if the property does not exist. If the default initial value is too complex and should not be evaluated every time when the property is get, or to throw an exception for an uninitialized property use the other Get overload. For an example, see the Remarks section of the ObservableObjectBase class. (Inherited from ObservableObjectBase)
OnPropertyChanged	Raises the PropertyChanged event. (Overrides ObservableObjectBaseOnPropertyChanged(PropertyChangedExtendedEventArgs))
ResetProperty	Resets the property of the specified name, meaning, it will be removed from the underlying storage so the getter methods will return the default value again. (Inherited from ObservableObjectBase)
ResumeChangedEvent	Resumes the raising of the PropertyChanged event suspended by the SuspendChangeEvents method. (Inherited from ObservableObjectBase)
Set	Sets the value of a property. For an example, see the Remarks section of the ObservableObjectBase class. (Inherited from ObservableObjectBase)
SetModified	Sets the modified state of this ObservableObjectBase instance represented by the IsModified property. (Inherited from ObservableObjectBase)
SuspendChangedEvent	Suspends the raising of the PropertyChanged event until ResumeChangeEvents method is called. Supports nested calls. (Inherited from ObservableObjectBase)
Validate	Forces calling the DoValidation method and updates the ValidationResults and IsValid properties.

Events

PropertyChanged

Occurs when a property value changed. The actual type of the event argument is PropertyChangedExtendedEventArgs.
(Inherited from ObservableObjectBase)

Extension Methods

Convert	Converts an Object specified in the obj parameter to the desired targetType. See the Examples section of the generic ConvertTTarget(Object, CultureInfo) overload for an example. (Defined by ObjectExtensions)
ConvertTTarget	Converts an Object specified in the obj parameter to the desired TTarget. (Defined by ObjectExtensions)
In	Gets whether item is among the elements of set. See the Examples section of the generic InT(T, T) overload for an example. (Defined by ObjectExtensions)
TryConvert	Tries to convert an Object specified in the obj parameter to the desired targetType. See the Examples section of the ConvertTTarget(Object, CultureInfo) method for a related example. (Defined by ObjectExtensions)
TryConvert	Tries to convert an Object specified in the obj parameter to the desired targetType. See the Examples section of the ConvertTTarget(Object, CultureInfo) method for a related example. (Defined by ObjectExtensions)
TryConvertTTarget	Tries to convert an Object specified in the obj parameter to the desired TTarget. See the Examples section of the ConvertTTarget(Object, CultureInfo) method for a related example. (Defined by ObjectExtensions)
TryConvertTTarget	Tries to convert an Object specified in the obj parameter to the desired TTarget. See the Examples section of the ConvertTTarget(Object, CultureInfo) method for a related example. (Defined by ObjectExtensions)