Comment : déterminer si un format de données est présent dans un objet de données
Les exemples suivants indiquent comment utiliser les différentes surcharges de méthode GetDataPresent pour vérifier si un format de données particulier est présent dans un objet de données.
Exemple
Description
L'exemple de code suivant utilise la surcharge GetDataPresent(String) pour chercher la présence d'un format de données particulier par chaîne de descripteur.
Code
Dim dataObject As New DataObject("Some string data to store...")
' Query for the presence of Text data in the data object, by a data format descriptor string.
' In this overload of GetDataPresent, the method will return true both for native data formats
' and when the data can automatically be converted to the specifed format.
' In this case, string data is present natively, so GetDataPresent returns "true".
Dim textData As String = Nothing
If dataObject.GetDataPresent(DataFormats.StringFormat) Then
textData = TryCast(dataObject.GetData(DataFormats.StringFormat), String)
End If
' In this case, the Text data in the data object can be autoconverted to
' Unicode text, so GetDataPresent returns "true".
Dim unicodeData() As Byte = Nothing
If dataObject.GetDataPresent(DataFormats.UnicodeText) Then
unicodeData = TryCast(dataObject.GetData(DataFormats.UnicodeText), Byte())
End If
DataObject dataObject = new DataObject("Some string data to store...");
// Query for the presence of Text data in the data object, by a data format descriptor string.
// In this overload of GetDataPresent, the method will return true both for native data formats
// and when the data can automatically be converted to the specifed format.
// In this case, string data is present natively, so GetDataPresent returns "true".
string textData = null;
if (dataObject.GetDataPresent(DataFormats.StringFormat))
{
textData = dataObject.GetData(DataFormats.StringFormat) as string;
}
// In this case, the Text data in the data object can be autoconverted to
// Unicode text, so GetDataPresent returns "true".
byte[] unicodeData = null;
if (dataObject.GetDataPresent(DataFormats.UnicodeText))
{
unicodeData = dataObject.GetData(DataFormats.UnicodeText) as byte[];
}
Exemple
Description
L'exemple de code suivant utilise la surcharge GetDataPresent(Type) pour chercher la présence d'un format de données particulier par type.
Code
Dim dataObject As New DataObject("Some string data to store...")
' Query for the presence of String data in the data object, by type. In this overload
' of GetDataPresent, the method will return true both for native data formats
' and when the data can automatically be converted to the specifed format.
' In this case, the Text data present in the data object can be autoconverted
' to type string (also represented by DataFormats.String), so GetDataPresent returns "true".
Dim stringData As String = Nothing
If dataObject.GetDataPresent(GetType(String)) Then
stringData = TryCast(dataObject.GetData(DataFormats.Text), String)
End If
DataObject dataObject = new DataObject("Some string data to store...");
// Query for the presence of String data in the data object, by type. In this overload
// of GetDataPresent, the method will return true both for native data formats
// and when the data can automatically be converted to the specifed format.
// In this case, the Text data present in the data object can be autoconverted
// to type string (also represented by DataFormats.String), so GetDataPresent returns "true".
string stringData = null;
if (dataObject.GetDataPresent(typeof(string)))
{
stringData = dataObject.GetData(DataFormats.Text) as string;
}
Exemple
Description
Le code d'exemple suivant utilise la surcharge GetDataPresent(String, Boolean) pour chercher des données par chaîne de descripteur, en spécifiant comment traiter des formats de données convertibles automatiquement.
Code
Dim dataObject As New DataObject("Some string data to store...")
' Query for the presence of Text data in the data object, by data format descriptor string,
' and specifying whether auto-convertible data formats are acceptable.
' In this case, Text data is present natively, so GetDataPresent returns "true".
Dim textData As String = Nothing
If dataObject.GetDataPresent(DataFormats.Text, False) Then ' Auto-convert?
textData = TryCast(dataObject.GetData(DataFormats.Text), String)
End If
' In this case, the Text data in the data object can be autoconverted to
' Unicode text, but it is not available natively, so GetDataPresent returns "false".
Dim unicodeData() As Byte = Nothing
If dataObject.GetDataPresent(DataFormats.UnicodeText, False) Then ' Auto-convert?
unicodeData = TryCast(dataObject.GetData(DataFormats.UnicodeText), Byte())
End If
' In this case, the Text data in the data object can be autoconverted to
' Unicode text, so GetDataPresent returns "true".
If dataObject.GetDataPresent(DataFormats.UnicodeText, True) Then ' Auto-convert?
unicodeData = TryCast(dataObject.GetData(DataFormats.UnicodeText), Byte())
End If
DataObject dataObject = new DataObject("Some string data to store...");
// Query for the presence of Text data in the data object, by data format descriptor string,
// and specifying whether auto-convertible data formats are acceptable.
// In this case, Text data is present natively, so GetDataPresent returns "true".
string textData = null;
if (dataObject.GetDataPresent(DataFormats.Text, false /* Auto-convert? */))
{
textData = dataObject.GetData(DataFormats.Text) as string;
}
// In this case, the Text data in the data object can be autoconverted to
// Unicode text, but it is not available natively, so GetDataPresent returns "false".
byte[] unicodeData = null;
if (dataObject.GetDataPresent(DataFormats.UnicodeText, false /* Auto-convert? */))
{
unicodeData = dataObject.GetData(DataFormats.UnicodeText) as byte[];
}
// In this case, the Text data in the data object can be autoconverted to
// Unicode text, so GetDataPresent returns "true".
if (dataObject.GetDataPresent(DataFormats.UnicodeText, true /* Auto-convert? */))
{
unicodeData = dataObject.GetData(DataFormats.UnicodeText) as byte[];
}