DataBoundControl.PerformSelect DataBoundControl.PerformSelect DataBoundControl.PerformSelect DataBoundControl.PerformSelect Method

Definizione

Recupera i dati dall'origine dati associata.Retrieves data from the associated data source.

protected:
 override void PerformSelect();
protected override void PerformSelect ();
override this.PerformSelect : unit -> unit
Protected Overrides Sub PerformSelect ()

Esempi

Nell'esempio di codice riportato di seguito viene illustrato PerformSelect come eseguire l'override del metodo per recuperare i dati da GetData un'origine dati associata utilizzando il metodo e associarli agli elementi del controllo.The following code example demonstrates how to override the PerformSelect method to retrieve data from an associated data source using the GetData method and bind it to the elements of the control. Questo esempio di codice fa parte di un esempio più ampio fornito DataBoundControl per la classe.This code example is part of a larger example provided for the DataBoundControl class.

protected override void PerformSelect() {            

   // Call OnDataBinding here if bound to a data source using the
   // DataSource property (instead of a DataSourceID), because the
   // databinding statement is evaluated before the call to GetData.       
    if (! IsBoundUsingDataSourceID) {
        OnDataBinding(EventArgs.Empty);
    }            
    
    // The GetData method retrieves the DataSourceView object from  
    // the IDataSource associated with the data-bound control.            
    GetData().Select(CreateDataSourceSelectArguments(), 
        OnDataSourceViewSelectCallback);
    
    // The PerformDataBinding method has completed.
    RequiresDataBinding = false;
    MarkAsDataBound();
    
    // Raise the DataBound event.
    OnDataBound(EventArgs.Empty);
}
Protected Overrides Sub PerformSelect()

    ' Call OnDataBinding here if bound to a data source using the 
    ' DataSource property (instead of a DataSourceID) because the 
    ' data-binding statement is evaluated before the call to GetData.
    If Not IsBoundUsingDataSourceID Then
        OnDataBinding(EventArgs.Empty)
    End If

    ' The GetData method retrieves the DataSourceView object from the 
    ' IDataSource associated with the data-bound control.            
    GetData().Select(CreateDataSourceSelectArguments(), _
        AddressOf OnDataSourceViewSelectCallback)

    ' The PerformDataBinding method has completed.
    RequiresDataBinding = False
    MarkAsDataBound()

    ' Raise the DataBound event.
        OnDataBound(EventArgs.Empty)

End Sub

Commenti

Il PerformDataBinding metodo viene chiamato dopo che i dati vengono recuperati per associare i dati agli elementi del controllo associato a dati.The PerformDataBinding method is called after data is retrieved to bind data to elements of the data-bound control. I tipi derivati eseguono l'override di questo metodo per recuperare i dati solo se l'implementazione predefinita non è adeguata.Derived types override this method to retrieve data only if the default implementation is not adequate. In genere, è sufficiente fornire un DataSourceViewSelectCallback delegato che esegua qualsiasi operazione di dati personalizzata, anziché implementare il PerformDataBinding metodo.Typically, it is sufficient to provide a DataSourceViewSelectCallback delegate that performs any custom data work, rather than implementing the PerformDataBinding method.

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