AsyncDownloadPolicy.Probing Event

Allows you to detect and intercept attempts to probe the availability of external resources before a connection request occurs.

Namespace: DevExpress.Data

Assembly: DevExpress.Data.v26.1.dll

Declaration

C#

public static event AsyncDownloadPolicy.WeakEventHandler<AsyncDownloadPolicy.ProbingEventArgs> Probing

VB.NET

Public Shared Event Probing As AsyncDownloadPolicy.WeakEventHandler(Of AsyncDownloadPolicy.ProbingEventArgs)

Event Data

The Probing event's data class is AsyncDownloadPolicy.ProbingEventArgs. The following properties provide information specific to this event:

Property	Description
Cancel	Gets or sets a value indicating whether the event should be canceled. Inherited from CancelEventArgs.
IsTrustedUri	Gets whether the processed resource is in a “safe” resource whitelist. Inherited from AsyncDownloadPolicy.AsyncDownloaderCancelEventArgs.
ThrowOnNonTrustedUri	Gets or sets whether to throw an exception for unwanted download requests. Inherited from AsyncDownloadPolicy.AsyncDownloaderCancelEventArgs.
Uri	Gets the processed resource identifier. Inherited from AsyncDownloadPolicy.AsyncDownloaderCancelEventArgs.

Remarks

The Probing event occurs when a control checks whether an external resource is available without downloading its content. The event allows you to detect and optionally cancel probe requests.

C#

void OnProbing(object sender, ProbingEventArgs e) {
    var shouldClose = XtraMessageBox.Show("Notification",
        "Probing the " + e.Uri.AbsoluteUri + " URL was detected. Close the connection?",
        MessageBoxButtons.YesNo);
    e.Cancel = (shouldClose == DialogResult.Yes) ? true : false;
}

VB.NET

Private Sub OnProbing(ByVal sender As Object, ByVal e As ProbingEventArgs)
    Dim shouldClose = XtraMessageBox.Show("Notification", "Probing the " & e.Uri.AbsoluteUri & " URL was detected. Close the connection?", MessageBoxButtons.YesNo)
    e.Cancel = If((shouldClose = DialogResult.Yes), True, False)
End Sub

Read the following topic for detailed information and examples: Suppress Control Requests to Download Data from External URLs.

Note

In the current implementation, only the Map Control and certain design-time wizards use probing requests. Other UI controls and components send connection requests directly and do not trigger the Probing event.