DictionaryBase.OnValidate(Object, Object) Method
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Performs additional custom processes when validating the element with the specified key and value.
protected:
virtual void OnValidate(System::Object ^ key, System::Object ^ value);
protected virtual void OnValidate (object key, object value);
protected virtual void OnValidate (object key, object? value);
abstract member OnValidate : obj * obj -> unit
override this.OnValidate : obj * obj -> unit
Protected Overridable Sub OnValidate (key As Object, value As Object)
- key
- Object
The key of the element to validate.
- value
- Object
The value of the element to validate.
The following code example implements the DictionaryBase class and uses that implementation to create a dictionary of String keys and values that have a Length of 5 characters or less.
using namespace System;
using namespace System::Collections;
public ref class ShortStringDictionary: public DictionaryBase
{
public:
property String^ Item [String^]
{
String^ get( String^ key )
{
return (dynamic_cast<String^>(Dictionary[ key ]));
}
void set( String^ value, String^ key )
{
Dictionary[ key ] = value;
}
}
property ICollection^ Keys
{
ICollection^ get()
{
return (Dictionary->Keys);
}
}
property ICollection^ Values
{
ICollection^ get()
{
return (Dictionary->Values);
}
}
void Add( String^ key, String^ value )
{
Dictionary->Add( key, value );
}
bool Contains( String^ key )
{
return (Dictionary->Contains( key ));
}
void Remove( String^ key )
{
Dictionary->Remove( key );
}
protected:
virtual void OnInsert( Object^ key, Object^ value ) override
{
if ( key->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "key must be of type String.","key" );
else
{
String^ strKey = dynamic_cast<String^>(key);
if ( strKey->Length > 5 )
throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
}
if ( value->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "value must be of type String.","value" );
else
{
String^ strValue = dynamic_cast<String^>(value);
if ( strValue->Length > 5 )
throw gcnew ArgumentException( "value must be no more than 5 characters in length.","value" );
}
}
virtual void OnRemove( Object^ key, Object^ /*value*/ ) override
{
if ( key->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "key must be of type String.","key" );
else
{
String^ strKey = dynamic_cast<String^>(key);
if ( strKey->Length > 5 )
throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
}
}
virtual void OnSet( Object^ key, Object^ /*oldValue*/, Object^ newValue ) override
{
if ( key->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "key must be of type String.","key" );
else
{
String^ strKey = dynamic_cast<String^>(key);
if ( strKey->Length > 5 )
throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
}
if ( newValue->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "newValue must be of type String.","newValue" );
else
{
String^ strValue = dynamic_cast<String^>(newValue);
if ( strValue->Length > 5 )
throw gcnew ArgumentException( "newValue must be no more than 5 characters in length.","newValue" );
}
}
virtual void OnValidate( Object^ key, Object^ value ) override
{
if ( key->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "key must be of type String.","key" );
else
{
String^ strKey = dynamic_cast<String^>(key);
if ( strKey->Length > 5 )
throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
}
if ( value->GetType() != Type::GetType( "System.String" ) )
throw gcnew ArgumentException( "value must be of type String.","value" );
else
{
String^ strValue = dynamic_cast<String^>(value);
if ( strValue->Length > 5 )
throw gcnew ArgumentException( "value must be no more than 5 characters in length.","value" );
}
}
};
void PrintKeysAndValues2( ShortStringDictionary^ myCol );
void PrintKeysAndValues3( ShortStringDictionary^ myCol );
int main()
{
// Creates and initializes a new DictionaryBase.
ShortStringDictionary^ mySSC = gcnew ShortStringDictionary;
// Adds elements to the collection.
mySSC->Add( "One", "a" );
mySSC->Add( "Two", "ab" );
mySSC->Add( "Three", "abc" );
mySSC->Add( "Four", "abcd" );
mySSC->Add( "Five", "abcde" );
// Display the contents of the collection using the enumerator.
Console::WriteLine( "Contents of the collection (using enumerator):" );
PrintKeysAndValues2( mySSC );
// Display the contents of the collection using the Keys property and the Item property.
Console::WriteLine( "Initial contents of the collection (using Keys and Item):" );
PrintKeysAndValues3( mySSC );
// Tries to add a value that is too long.
try
{
mySSC->Add( "Ten", "abcdefghij" );
}
catch ( ArgumentException^ e )
{
Console::WriteLine( e );
}
// Tries to add a key that is too long.
try
{
mySSC->Add( "Eleven", "ijk" );
}
catch ( ArgumentException^ e )
{
Console::WriteLine( e );
}
Console::WriteLine();
// Searches the collection with Contains.
Console::WriteLine( "Contains \"Three\": {0}", mySSC->Contains( "Three" ) );
Console::WriteLine( "Contains \"Twelve\": {0}", mySSC->Contains( "Twelve" ) );
Console::WriteLine();
// Removes an element from the collection.
mySSC->Remove( "Two" );
// Displays the contents of the collection.
Console::WriteLine( "After removing \"Two\":" );
PrintKeysAndValues2( mySSC );
}
// Uses the enumerator.
void PrintKeysAndValues2( ShortStringDictionary^ myCol )
{
DictionaryEntry myDE;
System::Collections::IEnumerator^ myEnumerator = myCol->GetEnumerator();
while ( myEnumerator->MoveNext() )
if ( myEnumerator->Current != nullptr )
{
myDE = *dynamic_cast<DictionaryEntry^>(myEnumerator->Current);
Console::WriteLine( " {0,-5} : {1}", myDE.Key, myDE.Value );
}
Console::WriteLine();
}
// Uses the Keys property and the Item property.
void PrintKeysAndValues3( ShortStringDictionary^ myCol )
{
ICollection^ myKeys = myCol->Keys;
IEnumerator^ myEnum1 = myKeys->GetEnumerator();
while ( myEnum1->MoveNext() )
{
String^ k = safe_cast<String^>(myEnum1->Current);
Console::WriteLine( " {0,-5} : {1}", k, myCol->Item[ k ] );
}
Console::WriteLine();
}
/*
This code produces the following output.
Contents of the collection (using enumerator):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
Initial contents of the collection (using Keys and Item):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
System.ArgumentException: value must be no more than 5 characters in length.
Parameter name: value
at ShortStringDictionary.OnValidate(Object key, Object value)
at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
at SamplesDictionaryBase.Main()
System.ArgumentException: key must be no more than 5 characters in length.
Parameter name: key
at ShortStringDictionary.OnValidate(Object key, Object value)
at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
at SamplesDictionaryBase.Main()
Contains "Three": True
Contains "Twelve": False
After removing "Two":
Three : abc
Five : abcde
One : a
Four : abcd
*/
using System;
using System.Collections;
public class ShortStringDictionary : DictionaryBase {
public String this[ String key ] {
get {
return( (String) Dictionary[key] );
}
set {
Dictionary[key] = value;
}
}
public ICollection Keys {
get {
return( Dictionary.Keys );
}
}
public ICollection Values {
get {
return( Dictionary.Values );
}
}
public void Add( String key, String value ) {
Dictionary.Add( key, value );
}
public bool Contains( String key ) {
return( Dictionary.Contains( key ) );
}
public void Remove( String key ) {
Dictionary.Remove( key );
}
protected override void OnInsert( Object key, Object value ) {
if ( key.GetType() != typeof(System.String) )
{
throw new ArgumentException( "key must be of type String.", "key" );
}
else {
String strKey = (String) key;
if ( strKey.Length > 5 )
throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
}
if ( value.GetType() != typeof(System.String) )
{
throw new ArgumentException( "value must be of type String.", "value" );
}
else {
String strValue = (String) value;
if ( strValue.Length > 5 )
throw new ArgumentException( "value must be no more than 5 characters in length.", "value" );
}
}
protected override void OnRemove( Object key, Object value ) {
if ( key.GetType() != typeof(System.String) )
{
throw new ArgumentException( "key must be of type String.", "key" );
}
else {
String strKey = (String) key;
if ( strKey.Length > 5 )
throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
}
}
protected override void OnSet( Object key, Object oldValue, Object newValue ) {
if ( key.GetType() != typeof(System.String) )
{
throw new ArgumentException( "key must be of type String.", "key" );
}
else {
String strKey = (String) key;
if ( strKey.Length > 5 )
throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
}
if ( newValue.GetType() != typeof(System.String) )
{
throw new ArgumentException( "newValue must be of type String.", "newValue" );
}
else {
String strValue = (String) newValue;
if ( strValue.Length > 5 )
throw new ArgumentException( "newValue must be no more than 5 characters in length.", "newValue" );
}
}
protected override void OnValidate( Object key, Object value ) {
if ( key.GetType() != typeof(System.String) )
{
throw new ArgumentException( "key must be of type String.", "key" );
}
else {
String strKey = (String) key;
if ( strKey.Length > 5 )
throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
}
if ( value.GetType() != typeof(System.String) )
{
throw new ArgumentException( "value must be of type String.", "value" );
}
else {
String strValue = (String) value;
if ( strValue.Length > 5 )
throw new ArgumentException( "value must be no more than 5 characters in length.", "value" );
}
}
}
public class SamplesDictionaryBase {
public static void Main() {
// Creates and initializes a new DictionaryBase.
ShortStringDictionary mySSC = new ShortStringDictionary();
// Adds elements to the collection.
mySSC.Add( "One", "a" );
mySSC.Add( "Two", "ab" );
mySSC.Add( "Three", "abc" );
mySSC.Add( "Four", "abcd" );
mySSC.Add( "Five", "abcde" );
// Display the contents of the collection using foreach. This is the preferred method.
Console.WriteLine( "Contents of the collection (using foreach):" );
PrintKeysAndValues1( mySSC );
// Display the contents of the collection using the enumerator.
Console.WriteLine( "Contents of the collection (using enumerator):" );
PrintKeysAndValues2( mySSC );
// Display the contents of the collection using the Keys property and the Item property.
Console.WriteLine( "Initial contents of the collection (using Keys and Item):" );
PrintKeysAndValues3( mySSC );
// Tries to add a value that is too long.
try {
mySSC.Add( "Ten", "abcdefghij" );
}
catch ( ArgumentException e ) {
Console.WriteLine( e.ToString() );
}
// Tries to add a key that is too long.
try {
mySSC.Add( "Eleven", "ijk" );
}
catch ( ArgumentException e ) {
Console.WriteLine( e.ToString() );
}
Console.WriteLine();
// Searches the collection with Contains.
Console.WriteLine( "Contains \"Three\": {0}", mySSC.Contains( "Three" ) );
Console.WriteLine( "Contains \"Twelve\": {0}", mySSC.Contains( "Twelve" ) );
Console.WriteLine();
// Removes an element from the collection.
mySSC.Remove( "Two" );
// Displays the contents of the collection.
Console.WriteLine( "After removing \"Two\":" );
PrintKeysAndValues1( mySSC );
}
// Uses the foreach statement which hides the complexity of the enumerator.
// NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
public static void PrintKeysAndValues1( ShortStringDictionary myCol ) {
foreach ( DictionaryEntry myDE in myCol )
Console.WriteLine( " {0,-5} : {1}", myDE.Key, myDE.Value );
Console.WriteLine();
}
// Uses the enumerator.
// NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
public static void PrintKeysAndValues2( ShortStringDictionary myCol ) {
DictionaryEntry myDE;
System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
while ( myEnumerator.MoveNext() )
if ( myEnumerator.Current != null ) {
myDE = (DictionaryEntry) myEnumerator.Current;
Console.WriteLine( " {0,-5} : {1}", myDE.Key, myDE.Value );
}
Console.WriteLine();
}
// Uses the Keys property and the Item property.
public static void PrintKeysAndValues3( ShortStringDictionary myCol ) {
ICollection myKeys = myCol.Keys;
foreach ( String k in myKeys )
Console.WriteLine( " {0,-5} : {1}", k, myCol[k] );
Console.WriteLine();
}
}
/*
This code produces the following output.
Contents of the collection (using foreach):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
Contents of the collection (using enumerator):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
Initial contents of the collection (using Keys and Item):
Three : abc
Five : abcde
Two : ab
One : a
Four : abcd
System.ArgumentException: value must be no more than 5 characters in length.
Parameter name: value
at ShortStringDictionary.OnValidate(Object key, Object value)
at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
at SamplesDictionaryBase.Main()
System.ArgumentException: key must be no more than 5 characters in length.
Parameter name: key
at ShortStringDictionary.OnValidate(Object key, Object value)
at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
at SamplesDictionaryBase.Main()
Contains "Three": True
Contains "Twelve": False
After removing "Two":
Three : abc
Five : abcde
One : a
Four : abcd
*/
Imports System.Collections
Public Class ShortStringDictionary
Inherits DictionaryBase
Default Public Property Item(key As String) As String
Get
Return CType(Dictionary(key), String)
End Get
Set
Dictionary(key) = value
End Set
End Property
Public ReadOnly Property Keys() As ICollection
Get
Return Dictionary.Keys
End Get
End Property
Public ReadOnly Property Values() As ICollection
Get
Return Dictionary.Values
End Get
End Property
Public Sub Add(key As String, value As String)
Dictionary.Add(key, value)
End Sub
Public Function Contains(key As String) As Boolean
Return Dictionary.Contains(key)
End Function 'Contains
Public Sub Remove(key As String)
Dictionary.Remove(key)
End Sub
Protected Overrides Sub OnInsert(key As Object, value As Object)
If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As String = CType(key, String)
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
If Not GetType(System.String).IsAssignableFrom(value.GetType()) Then
Throw New ArgumentException("value must be of type String.", "value")
Else
Dim strValue As String = CType(value, String)
If strValue.Length > 5 Then
Throw New ArgumentException("value must be no more than 5 characters in length.", "value")
End If
End If
End Sub
Protected Overrides Sub OnRemove(key As Object, value As Object)
If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As String = CType(key, String)
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
End Sub
Protected Overrides Sub OnSet(key As Object, oldValue As Object, newValue As Object)
If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As String = CType(key, String)
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
If Not GetType(System.String).IsAssignableFrom(newValue.GetType()) Then
Throw New ArgumentException("newValue must be of type String.", "newValue")
Else
Dim strValue As String = CType(newValue, String)
If strValue.Length > 5 Then
Throw New ArgumentException("newValue must be no more than 5 characters in length.", "newValue")
End If
End If
End Sub
Protected Overrides Sub OnValidate(key As Object, value As Object)
If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As String = CType(key, String)
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
If Not GetType(System.String).IsAssignableFrom(value.GetType()) Then
Throw New ArgumentException("value must be of type String.", "value")
Else
Dim strValue As String = CType(value, String)
If strValue.Length > 5 Then
Throw New ArgumentException("value must be no more than 5 characters in length.", "value")
End If
End If
End Sub
End Class
Public Class SamplesDictionaryBase
Public Shared Sub Main()
' Creates and initializes a new DictionaryBase.
Dim mySSC As New ShortStringDictionary()
' Adds elements to the collection.
mySSC.Add("One", "a")
mySSC.Add("Two", "ab")
mySSC.Add("Three", "abc")
mySSC.Add("Four", "abcd")
mySSC.Add("Five", "abcde")
' Display the contents of the collection using For Each. This is the preferred method.
Console.WriteLine("Contents of the collection (using For Each):")
PrintKeysAndValues1(mySSC)
' Display the contents of the collection using the enumerator.
Console.WriteLine("Contents of the collection (using enumerator):")
PrintKeysAndValues2(mySSC)
' Display the contents of the collection using the Keys property and the Item property.
Console.WriteLine("Initial contents of the collection (using Keys and Item):")
PrintKeysAndValues3(mySSC)
' Tries to add a value that is too long.
Try
mySSC.Add("Ten", "abcdefghij")
Catch e As ArgumentException
Console.WriteLine(e.ToString())
End Try
' Tries to add a key that is too long.
Try
mySSC.Add("Eleven", "ijk")
Catch e As ArgumentException
Console.WriteLine(e.ToString())
End Try
Console.WriteLine()
' Searches the collection with Contains.
Console.WriteLine("Contains ""Three"": {0}", mySSC.Contains("Three"))
Console.WriteLine("Contains ""Twelve"": {0}", mySSC.Contains("Twelve"))
Console.WriteLine()
' Removes an element from the collection.
mySSC.Remove("Two")
' Displays the contents of the collection.
Console.WriteLine("After removing ""Two"":")
PrintKeysAndValues1(mySSC)
End Sub
' Uses the For Each statement which hides the complexity of the enumerator.
' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
Public Shared Sub PrintKeysAndValues1(myCol As ShortStringDictionary)
Dim myDE As DictionaryEntry
For Each myDE In myCol
Console.WriteLine(" {0,-5} : {1}", myDE.Key, myDE.Value)
Next myDE
Console.WriteLine()
End Sub
' Uses the enumerator.
' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
Public Shared Sub PrintKeysAndValues2(myCol As ShortStringDictionary)
Dim myDE As DictionaryEntry
Dim myEnumerator As System.Collections.IEnumerator = myCol.GetEnumerator()
While myEnumerator.MoveNext()
If Not (myEnumerator.Current Is Nothing) Then
myDE = CType(myEnumerator.Current, DictionaryEntry)
Console.WriteLine(" {0,-5} : {1}", myDE.Key, myDE.Value)
End If
End While
Console.WriteLine()
End Sub
' Uses the Keys property and the Item property.
Public Shared Sub PrintKeysAndValues3(myCol As ShortStringDictionary)
Dim myKeys As ICollection = myCol.Keys
Dim k As String
For Each k In myKeys
Console.WriteLine(" {0,-5} : {1}", k, myCol(k))
Next k
Console.WriteLine()
End Sub
End Class
'This code produces the following output.
'
'Contents of the collection (using For Each):
' Three : abc
' Five : abcde
' Two : ab
' One : a
' Four : abcd
'
'Contents of the collection (using enumerator):
' Three : abc
' Five : abcde
' Two : ab
' One : a
' Four : abcd
'
'Initial contents of the collection (using Keys and Item):
' Three : abc
' Five : abcde
' Two : ab
' One : a
' Four : abcd
'
'System.ArgumentException: value must be no more than 5 characters in length.
'Parameter name: value
' at ShortStringDictionary.OnValidate(Object key, Object value)
' at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
' at SamplesDictionaryBase.Main()
'System.ArgumentException: key must be no more than 5 characters in length.
'Parameter name: key
' at ShortStringDictionary.OnValidate(Object key, Object value)
' at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
' at SamplesDictionaryBase.Main()
'
'Contains "Three": True
'Contains "Twelve": False
'
'After removing "Two":
' Three : abc
' Five : abcde
' One : a
' Four : abcd
The default implementation of this method is intended to be overridden by a derived class to perform some action when the specified element is validated.
The On* methods are invoked only on the instance returned by the Dictionary property, but not on the instance returned by the InnerHashtable property.
The default implementation of this method is an O(1)
operation.
This method allows implementers to define processes that must be performed when executing the standard behavior of the underlying Hashtable. By defining this method, implementers can add functionality to inherited methods without having to override all other methods.
OnValidate(Object, Object) can be used to impose restrictions on the type of objects that are accepted into the collection. The default implementation prevents null
from being added to or removed from the underlying Hashtable.
Product | Versions |
---|---|
.NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
.NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
.NET Standard | 2.0, 2.1 |
UWP | 10.0 |
.NET feedback
.NET is an open source project. Select a link to provide feedback: