Control.Invoke Control.Invoke Control.Invoke Control.Invoke Method

Definição

Executa um delegado no thread que possui o identificador de janela subjacente do controle.Executes a delegate on the thread that owns the control's underlying window handle.

Sobrecargas

Invoke(Delegate) Invoke(Delegate) Invoke(Delegate) Invoke(Delegate)

Executa o delegado especificado no thread que possui o identificador de janela subjacente do controle.Executes the specified delegate on the thread that owns the control's underlying window handle.

Invoke(Delegate, Object[]) Invoke(Delegate, Object[]) Invoke(Delegate, Object[]) Invoke(Delegate, Object[])

Executa o delegado especificado, no thread que tem o identificador da janela subjacente do controle, com a lista de argumentos especificada.Executes the specified delegate, on the thread that owns the control's underlying window handle, with the specified list of arguments.

Invoke(Delegate) Invoke(Delegate) Invoke(Delegate) Invoke(Delegate)

Executa o delegado especificado no thread que possui o identificador de janela subjacente do controle.Executes the specified delegate on the thread that owns the control's underlying window handle.

public:
 System::Object ^ Invoke(Delegate ^ method);
public object Invoke (Delegate method);
member this.Invoke : Delegate -> obj
Public Function Invoke (method As Delegate) As Object

Parâmetros

method
Delegate Delegate Delegate Delegate

Um delegado que contém um método a ser chamado no contexto do thread do controle.A delegate that contains a method to be called in the control's thread context.

Retornos

O valor retornado do delegado que está sendo invocado, ou null, se o delegado não tiver nenhum valor retornado.The return value from the delegate being invoked, or null if the delegate has no return value.

Exemplos

O exemplo de código a seguir mostra os controles que contêm um delegado.The following code example shows controls that contain a delegate. O delegado encapsula um método que adiciona itens à caixa de listagem e esse método é executado no thread que possui o identificador subjacente do formulário.The delegate encapsulates a method that adds items to the list box, and this method is executed on the thread that owns the underlying handle of the form. Quando o usuário clica no botão, Invoke executa o delegado.When the user clicks on the button, Invoke runs the delegate.

/*
The following example demonstrates the 'Invoke(Delegate*)' method of 'Control class.
A 'ListBox' and a 'Button' control are added to a form, containing a delegate
which encapsulates a method that adds items to the listbox.This function is executed
on the thread that owns the underlying handle of the form. When user clicks on button
the above delegate is executed using 'Invoke' method.
*/

#using <System.dll>
#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
using namespace System::Threading;

public ref class MyFormControl: public Form
{
public:
   delegate void AddListItem();
   AddListItem^ myDelegate;

private:
   Button^ myButton;
   Thread^ myThread;
   ListBox^ myListBox;

public:
   MyFormControl();
   void AddListItemMethod()
   {
      String^ myItem;
      for ( int i = 1; i < 6; i++ )
      {
         myItem = "MyListItem {0}",i;
         myListBox->Items->Add( myItem );
         myListBox->Update();
         Thread::Sleep( 300 );
      }
   }

private:
   void Button_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
   {
      myThread = gcnew Thread( gcnew ThreadStart( this, &MyFormControl::ThreadFunction ) );
      myThread->Start();
   }

   void ThreadFunction();
};


// The following code assumes a 'ListBox' and a 'Button' control are added to a form,
// containing a delegate which encapsulates a method that adds items to the listbox.
public ref class MyThreadClass
{
private:
   MyFormControl^ myFormControl1;

public:
   MyThreadClass( MyFormControl^ myForm )
   {
      myFormControl1 = myForm;
   }

   void Run()
   {
      // Execute the specified delegate on the thread that owns
      // 'myFormControl1' control's underlying window handle.
      myFormControl1->Invoke( myFormControl1->myDelegate );
   }
};


MyFormControl::MyFormControl()
{
   myButton = gcnew Button;
   myListBox = gcnew ListBox;
   myButton->Location = Point( 72, 160 );
   myButton->Size = System::Drawing::Size( 152, 32 );
   myButton->TabIndex = 1;
   myButton->Text = "Add items in list box";
   myButton->Click += gcnew EventHandler( this, &MyFormControl::Button_Click );
   myListBox->Location = Point( 48, 32 );
   myListBox->Name = "myListBox";
   myListBox->Size = System::Drawing::Size( 200, 95 );
   myListBox->TabIndex = 2;
   ClientSize = System::Drawing::Size( 292, 273 );
   array<Control^>^ temp0 = {myListBox,myButton};
   Controls->AddRange( temp0 );
   Text = " 'Control_Invoke' example";
   myDelegate = gcnew AddListItem( this, &MyFormControl::AddListItemMethod );
}

void MyFormControl::ThreadFunction()
{
   MyThreadClass^ myThreadClassObject = gcnew MyThreadClass( this );
   myThreadClassObject->Run();
}

int main()
{
   MyFormControl^ myForm = gcnew MyFormControl;
   myForm->ShowDialog();
}
/*
The following example demonstrates the 'Invoke(Delegate)' method of 'Control class.
A 'ListBox' and a 'Button' control are added to a form, containing a delegate
which encapsulates a method that adds items to the listbox.This function is executed
on the thread that owns the underlying handle of the form. When user clicks on button
the above delegate is executed using 'Invoke' method.


*/

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Threading;

   public class MyFormControl : Form
   {
      public delegate void AddListItem();
      public AddListItem myDelegate;
      private Button myButton;
      private Thread myThread;
      private ListBox myListBox;
      public MyFormControl()
      {
         myButton = new Button();
         myListBox = new ListBox();
         myButton.Location = new Point(72, 160);
         myButton.Size = new Size(152, 32);
         myButton.TabIndex = 1;
         myButton.Text = "Add items in list box";
         myButton.Click += new EventHandler(Button_Click);
         myListBox.Location = new Point(48, 32);
         myListBox.Name = "myListBox";
         myListBox.Size = new Size(200, 95);
         myListBox.TabIndex = 2;
         ClientSize = new Size(292, 273);
         Controls.AddRange(new Control[] {myListBox,myButton});
         Text = " 'Control_Invoke' example";
         myDelegate = new AddListItem(AddListItemMethod);
      }
      static void Main()
      {
         MyFormControl myForm = new MyFormControl();
         myForm.ShowDialog();
      }
      public void AddListItemMethod()
      {
         String myItem;
         for(int i=1;i<6;i++)
         {
            myItem = "MyListItem" + i.ToString();
            myListBox.Items.Add(myItem);
            myListBox.Update();
            Thread.Sleep(300);
         }
      }
      private void Button_Click(object sender, EventArgs e)
      {
         myThread = new Thread(new ThreadStart(ThreadFunction));
         myThread.Start();
      }
      private void ThreadFunction()
      {
         MyThreadClass myThreadClassObject  = new MyThreadClass(this);
         myThreadClassObject.Run();
      }
   }

// The following code assumes a 'ListBox' and a 'Button' control are added to a form, 
// containing a delegate which encapsulates a method that adds items to the listbox.

   public class MyThreadClass
   {
      MyFormControl myFormControl1;
      public MyThreadClass(MyFormControl myForm)
      {
         myFormControl1 = myForm;
      }

      public void Run()
      {
         // Execute the specified delegate on the thread that owns
         // 'myFormControl1' control's underlying window handle.
         myFormControl1.Invoke(myFormControl1.myDelegate);
      }
   }
' The following example demonstrates the 'Invoke(Delegate)' method of 'Control class.
' A 'ListBox' and a 'Button' control are added to a form, containing a delegate
' which encapsulates a method that adds items to the listbox.This function is executed
' on the thread that owns the underlying handle of the form. When user clicks on button
' the above delegate is executed using 'Invoke' method.

Imports System
Imports System.Drawing
Imports System.Windows.Forms
Imports System.Threading

Public Class MyFormControl
   Inherits Form

   Delegate Sub AddListItem()
   Public myDelegate As AddListItem
   Private myButton As Button
   Private myThread As Thread
   Private myListBox As ListBox

   Public Sub New()
      myButton = New Button()
      myListBox = New ListBox()
      myButton.Location = New Point(72, 160)
      myButton.Size = New Size(152, 32)
      myButton.TabIndex = 1
      myButton.Text = "Add items in list box"
      AddHandler myButton.Click, AddressOf Button_Click
      myListBox.Location = New Point(48, 32)
      myListBox.Name = "myListBox"
      myListBox.Size = New Size(200, 95)
      myListBox.TabIndex = 2
      ClientSize = New Size(292, 273)
      Controls.AddRange(New Control() {myListBox, myButton})
      Text = " 'Control_Invoke' example"
      myDelegate = New AddListItem(AddressOf AddListItemMethod)
   End Sub 'New

   Shared Sub Main()
      Dim myForm As New MyFormControl()
      myForm.ShowDialog()
   End Sub 'Main

   Public Sub AddListItemMethod()
      Dim myItem As String
      Dim i As Integer
      For i = 1 To 5
         myItem = "MyListItem" + i.ToString()
         myListBox.Items.Add(myItem)
         myListBox.Update()
         Thread.Sleep(300)
      Next i
   End Sub 'AddListItemMethod

   Private Sub Button_Click(sender As Object, e As EventArgs)
      myThread = New Thread(New ThreadStart(AddressOf ThreadFunction))
      myThread.Start()
   End Sub 'Button_Click

   Private Sub ThreadFunction()
      Dim myThreadClassObject As New MyThreadClass(Me)
      myThreadClassObject.Run()
   End Sub 'ThreadFunction
End Class 'MyFormControl


' The following code assumes a 'ListBox' and a 'Button' control are added to a form, 
' containing a delegate which encapsulates a method that adds items to the listbox.
Public Class MyThreadClass
   Private myFormControl1 As MyFormControl

   Public Sub New(myForm As MyFormControl)
      myFormControl1 = myForm
   End Sub 'New

   Public Sub Run()
      ' Execute the specified delegate on the thread that owns
      ' 'myFormControl1' control's underlying window handle.
      myFormControl1.Invoke(myFormControl1.myDelegate)
   End Sub 'Run

End Class 'MyThreadClass

Comentários

Os delegados são semelhantes a ponteiros de função nas linguagens C ou C++.Delegates are similar to function pointers in C or C++ languages. Delegados encapsulam uma referência a um método dentro de um objeto delegado.Delegates encapsulate a reference to a method inside a delegate object. O objeto delegado, em seguida, pode ser passado para o código que chama o método referenciado e o método a ser invocado pode ser desconhecido em tempo de compilação.The delegate object can then be passed to code that calls the referenced method, and the method to be invoked can be unknown at compile time. Ao contrário dos ponteiros de função em C ou C++, os delegados são orientados a objeto, fortemente tipada e mais seguras.Unlike function pointers in C or C++, delegates are object-oriented, type-safe, and more secure.

O Invoke método pesquisa a cadeia do pai do controle até encontrar um controle ou formulário que tenha uma janela de lidar com se o identificador de janela subjacente do controle atual ainda não existir.The Invoke method searches up the control's parent chain until it finds a control or form that has a window handle if the current control's underlying window handle does not exist yet. Se nenhum identificador apropriado pode ser encontrado, o Invoke método lançará uma exceção.If no appropriate handle can be found, the Invoke method will throw an exception. As exceções que são geradas durante a chamada serão propagadas para o chamador.Exceptions that are raised during the call will be propagated back to the caller.

Observação

Além de InvokeRequired propriedade, existem quatro métodos em um controle que são thread-safe: Invoke, BeginInvoke, EndInvoke, e CreateGraphics se o identificador para o controle já foi criado.In addition to the InvokeRequired property, there are four methods on a control that are thread safe: Invoke, BeginInvoke, EndInvoke, and CreateGraphics if the handle for the control has already been created. Chamar CreateGraphics antes de criar o identificador do controle em um thread em segundo plano pode causar ilegal entre chamadas do thread.Calling CreateGraphics before the control's handle has been created on a background thread can cause illegal cross thread calls. Para todas as outras chamadas de método, você deve usar um dos métodos invoke para realizar marshaling da chamada para thread do controle.For all other method calls, you should use one of the invoke methods to marshal the call to the control's thread.

O delegado pode ser uma instância do EventHandler, caso em que o parâmetro do remetente conterá esse controle e o parâmetro de evento conterá EventArgs.Empty.The delegate can be an instance of EventHandler, in which case the sender parameter will contain this control, and the event parameter will contain EventArgs.Empty. O delegado também pode ser uma instância de MethodInvoker, ou qualquer outro tipo de delegado que utiliza uma lista de parâmetros void.The delegate can also be an instance of MethodInvoker, or any other delegate that takes a void parameter list. Uma chamada para um EventHandler ou MethodInvoker delegado seja mais rápido do que uma chamada para outro tipo de delegado.A call to an EventHandler or MethodInvoker delegate will be faster than a call to another type of delegate.

Observação

Uma exceção seria lançada se o thread que deve processar a mensagem não está mais ativo.An exception might be thrown if the thread that should process the message is no longer active.

Veja também

Invoke(Delegate, Object[]) Invoke(Delegate, Object[]) Invoke(Delegate, Object[]) Invoke(Delegate, Object[])

Executa o delegado especificado, no thread que tem o identificador da janela subjacente do controle, com a lista de argumentos especificada.Executes the specified delegate, on the thread that owns the control's underlying window handle, with the specified list of arguments.

public:
 virtual System::Object ^ Invoke(Delegate ^ method, ... cli::array <System::Object ^> ^ args);
public object Invoke (Delegate method, params object[] args);
abstract member Invoke : Delegate * obj[] -> obj
override this.Invoke : Delegate * obj[] -> obj
Public Function Invoke (method As Delegate, ParamArray args As Object()) As Object

Parâmetros

method
Delegate Delegate Delegate Delegate

Um delegado para um método que usa parâmetros do mesmo número e tipo contidos no parâmetro args.A delegate to a method that takes parameters of the same number and type that are contained in the args parameter.

args
Object[]

Uma matriz de objetos a serem passados como argumentos para o método especificado.An array of objects to pass as arguments to the specified method. Esse parâmetro poderá ser null se o método não utilizar argumentos.This parameter can be null if the method takes no arguments.

Retornos

Um Object que contém um valor retornado do delegado que está sendo invocado, ou null, se o delegado não tiver um valor de retorno.An Object that contains the return value from the delegate being invoked, or null if the delegate has no return value.

Exemplos

O exemplo de código a seguir mostra os controles que contêm um delegado.The following code example shows controls that contain a delegate. O delegado encapsula um método que adiciona itens à caixa de listagem e esse método é executado no thread que possui o identificador subjacente do formulário, usando os argumentos especificados.The delegate encapsulates a method that adds items to the list box, and this method is executed on the thread that owns the underlying handle of the form, using the specified arguments. Quando o usuário clica no botão, Invoke executa o delegado.When the user clicks on the button, Invoke runs the delegate.

using namespace System;
using namespace System::Drawing;
using namespace System::ComponentModel;
using namespace System::Windows::Forms;
using namespace System::Threading;
ref class MyFormControl: public Form
{
public:
   delegate void AddListItem( String^ myString );
   AddListItem^ myDelegate;

private:
   Button^ myButton;
   Thread^ myThread;
   ListBox^ myListBox;

public:
   MyFormControl();
   void AddListItemMethod( String^ myString );

private:
   void Button_Click( Object^ sender, EventArgs^ e );
   void ThreadFunction();
};

ref class MyThreadClass
{
private:
   MyFormControl^ myFormControl1;

public:
   MyThreadClass( MyFormControl^ myForm )
   {
      myFormControl1 = myForm;
   }

   String^ myString;
   void Run()
   {
      for ( int i = 1; i <= 5; i++ )
      {
         myString = String::Concat( "Step number ", i, " executed" );
         Thread::Sleep( 400 );
         
         // Execute the specified delegate on the thread that owns
         // 'myFormControl1' control's underlying window handle with
         // the specified list of arguments.
         array<Object^>^myStringArray = {myString};
         myFormControl1->Invoke( myFormControl1->myDelegate, myStringArray );

      }
   }

};

MyFormControl::MyFormControl()
{
   myButton = gcnew Button;
   myListBox = gcnew ListBox;
   myButton->Location = Point(72,160);
   myButton->Size = System::Drawing::Size( 152, 32 );
   myButton->TabIndex = 1;
   myButton->Text = "Add items in list box";
   myButton->Click += gcnew EventHandler( this, &MyFormControl::Button_Click );
   myListBox->Location = Point(48,32);
   myListBox->Name = "myListBox";
   myListBox->Size = System::Drawing::Size( 200, 95 );
   myListBox->TabIndex = 2;
   ClientSize = System::Drawing::Size( 292, 273 );
   array<Control^>^formControls = {myListBox,myButton};
   Controls->AddRange( formControls );
   Text = " 'Control_Invoke' example ";
   myDelegate = gcnew AddListItem( this, &MyFormControl::AddListItemMethod );
}

void MyFormControl::AddListItemMethod( String^ myString )
{
   myListBox->Items->Add( myString );
}

void MyFormControl::Button_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
{
   myThread = gcnew Thread( gcnew ThreadStart( this, &MyFormControl::ThreadFunction ) );
   myThread->Start();
}

void MyFormControl::ThreadFunction()
{
   MyThreadClass^ myThreadClassObject = gcnew MyThreadClass( this );
   myThreadClassObject->Run();
}

int main()
{
   MyFormControl^ myForm = gcnew MyFormControl;
   myForm->ShowDialog();
}

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Threading;

   public class MyFormControl : Form
   {
      public delegate void AddListItem(String myString);
      public AddListItem myDelegate;
      private Button myButton;
      private Thread myThread;
      private ListBox myListBox;
      public MyFormControl()
      {
         myButton = new Button();
         myListBox = new ListBox();
         myButton.Location = new Point(72, 160);
         myButton.Size = new Size(152, 32);
         myButton.TabIndex = 1;
         myButton.Text = "Add items in list box";
         myButton.Click += new EventHandler(Button_Click);
         myListBox.Location = new Point(48, 32);
         myListBox.Name = "myListBox";
         myListBox.Size = new Size(200, 95);
         myListBox.TabIndex = 2;
         ClientSize = new Size(292, 273);
         Controls.AddRange(new Control[] {myListBox,myButton});
         Text = " 'Control_Invoke' example ";
         myDelegate = new AddListItem(AddListItemMethod);
      }
      static void Main()
      {
         MyFormControl myForm = new MyFormControl();
         myForm.ShowDialog();
      }
      public void AddListItemMethod(String myString)
      {
            myListBox.Items.Add(myString);
      }
      private void Button_Click(object sender, EventArgs e)
      {
         myThread = new Thread(new ThreadStart(ThreadFunction));
         myThread.Start();
      }
      private void ThreadFunction()
      {
         MyThreadClass myThreadClassObject  = new MyThreadClass(this);
         myThreadClassObject.Run();
      }
   }
   public class MyThreadClass
   {
      MyFormControl myFormControl1;
      public MyThreadClass(MyFormControl myForm)
      {
         myFormControl1 = myForm;
      }
      String myString;

      public void Run()
      {


         for (int i = 1; i <= 5; i++)
         {
            myString = "Step number " + i.ToString() + " executed";
            Thread.Sleep(400);
            // Execute the specified delegate on the thread that owns
            // 'myFormControl1' control's underlying window handle with
            // the specified list of arguments.
            myFormControl1.Invoke(myFormControl1.myDelegate,
                                   new Object[] {myString});
         }
      }
   }
Imports System
Imports System.Drawing
Imports System.Windows.Forms
Imports System.Threading

Public Class MyFormControl
   Inherits Form

   Delegate Sub AddListItem(myString As String)
   Public myDelegate As AddListItem
   Private myButton As Button
   Private myThread As Thread
   Private myListBox As ListBox

   Public Sub New()
      myButton = New Button()
      myListBox = New ListBox()
      myButton.Location = New Point(72, 160)
      myButton.Size = New Size(152, 32)
      myButton.TabIndex = 1
      myButton.Text = "Add items in list box"
      AddHandler myButton.Click, AddressOf Button_Click
      myListBox.Location = New Point(48, 32)
      myListBox.Name = "myListBox"
      myListBox.Size = New Size(200, 95)
      myListBox.TabIndex = 2
      ClientSize = New Size(292, 273)
      Controls.AddRange(New Control() {myListBox, myButton})
      Text = " 'Control_Invoke' example "
      myDelegate = New AddListItem(AddressOf AddListItemMethod)
   End Sub 'New

   Shared Sub Main()
      Dim myForm As New MyFormControl()
      myForm.ShowDialog()
   End Sub 'Main

   Public Sub AddListItemMethod(myString As String)
      myListBox.Items.Add(myString)
   End Sub 'AddListItemMethod

   Private Sub Button_Click(sender As Object, e As EventArgs)
      myThread = New Thread(New ThreadStart(AddressOf ThreadFunction))
      myThread.Start()
   End Sub 'Button_Click

   Private Sub ThreadFunction()
      Dim myThreadClassObject As New MyThreadClass(Me)
      myThreadClassObject.Run()
   End Sub 'ThreadFunction
End Class 'MyFormControl

Public Class MyThreadClass
   Private myFormControl1 As MyFormControl

   Public Sub New(myForm As MyFormControl)
      myFormControl1 = myForm
   End Sub 'New
   Private myString As String

   Public Sub Run()

      Dim i As Integer
      For i = 1 To 5
         myString = "Step number " + i.ToString() + " executed"
         Thread.Sleep(400)
         ' Execute the specified delegate on the thread that owns
         ' 'myFormControl1' control's underlying window handle with
         ' the specified list of arguments.
         myFormControl1.Invoke(myFormControl1.myDelegate, New Object() {myString})
      Next i

   End Sub 'Run
End Class 'MyThreadClass

Comentários

Os delegados são semelhantes a ponteiros de função nas linguagens C ou C++.Delegates are similar to function pointers in C or C++ languages. Delegados encapsulam uma referência a um método dentro de um objeto delegado.Delegates encapsulate a reference to a method inside a delegate object. O objeto delegado, em seguida, pode ser passado para o código que chama o método referenciado e o método a ser invocado pode ser desconhecido em tempo de compilação.The delegate object can then be passed to code that calls the referenced method, and the method to be invoked can be unknown at compile time. Ao contrário dos ponteiros de função em C ou C++, os delegados são orientados a objeto, fortemente tipada e mais seguras.Unlike function pointers in C or C++, delegates are object-oriented, type-safe, and more secure.

Se o identificador do controle ainda não existir, este método pesquisa cadeia do pai do controle até encontrar um controle ou formulário que tem um identificador de janela.If the control's handle does not exist yet, this method searches up the control's parent chain until it finds a control or form that does have a window handle. Se nenhum identificador apropriado pode ser encontrado, esse método gera uma exceção.If no appropriate handle can be found, this method throws an exception. As exceções que são geradas durante a chamada serão propagadas para o chamador.Exceptions that are raised during the call will be propagated back to the caller.

Observação

Além de InvokeRequired propriedade, existem quatro métodos em um controle que são thread-safe: Invoke, BeginInvoke, EndInvoke, e CreateGraphics se o identificador para o controle já foi criado.In addition to the InvokeRequired property, there are four methods on a control that are thread safe: Invoke, BeginInvoke, EndInvoke, and CreateGraphics if the handle for the control has already been created. Chamar CreateGraphics antes de criar o identificador do controle em um thread em segundo plano pode causar ilegal entre chamadas do thread.Calling CreateGraphics before the control's handle has been created on a background thread can cause illegal cross thread calls. Para todas as outras chamadas de método, você deve usar um dos métodos invoke para realizar marshaling da chamada para thread do controle.For all other method calls, you should use one of the invoke methods to marshal the call to the control's thread.

O delegado pode ser uma instância do EventHandler, caso em que o parâmetro do remetente conterá esse controle e o parâmetro de evento conterá EventArgs.Empty.The delegate can be an instance of EventHandler, in which case the sender parameter will contain this control, and the event parameter will contain EventArgs.Empty. O delegado também pode ser uma instância de MethodInvoker, ou qualquer outro tipo de delegado que utiliza uma lista de parâmetros void.The delegate can also be an instance of MethodInvoker, or any other delegate that takes a void parameter list. Uma chamada para um EventHandler ou MethodInvoker delegado seja mais rápido do que uma chamada para outro tipo de delegado.A call to an EventHandler or MethodInvoker delegate will be faster than a call to another type of delegate.

Observação

Uma exceção seria lançada se o thread que deve processar a mensagem não está mais ativo.An exception might be thrown if the thread that should process the message is no longer active.

Veja também

Aplica-se a