OracleConnectionStringBuilder.TryGetValue(String, Object) Metodo

Definizione

Spazio dei nomi:

System.Data.OracleClient

Assembly:

System.Data.OracleClient.dll

Recupera un valore che corrisponde alla chiave fornita da questo oggetto OracleConnectionStringBuilder.

public:
 override bool TryGetValue(System::String ^ keyword, [Runtime::InteropServices::Out] System::Object ^ % value);

public override bool TryGetValue (string keyword, out object value);

override this.TryGetValue : string * obj -> bool

Public Overrides Function TryGetValue (keyword As String, ByRef value As Object) As Boolean

Parametri

keyword

String

Chiave dell'elemento da recuperare.

value

Object

Valore corrispondente a keyword.

Restituisce

Boolean

true se keyword è stato rilevato all'interno della stringa di connessione; altrimenti, false.

Esempio

Nell'esempio TryGetValue seguente viene illustrato il comportamento del metodo.

// You may need to set a reference to the System.Data.OracleClient
// assembly before you can run this sample.
using System.Data.OracleClient;

class Program
{
    static void Main()
    {
        OracleConnectionStringBuilder builder = new OracleConnectionStringBuilder();
        builder.ConnectionString = GetConnectionString();

        // Call TryGetValue method for multiple
        // key names. Note that these keys are converted
        // to well-known synonynms for data retrieval.
        DisplayValue(builder, "Data Source");
        DisplayValue(builder, "Trusted_Connection");
        DisplayValue(builder, "InvalidKey");
        DisplayValue(builder, null);

        Console.WriteLine("Press any key to continue.");
        Console.ReadLine();
    }

    private static void DisplayValue(OracleConnectionStringBuilder builder, string key)
    {
        object value = null;

        // Although TryGetValue handles missing keys,
        // it does not handle passing in a null
        // key. This example traps for that particular error, but
        // passes any other unknown exceptions back out to the
        // caller.
        try
        {
            if (builder.TryGetValue(key, out value))
            {
                Console.WriteLine("{0}='{1}'", key, value);
            }
            else
            {
                Console.WriteLine("Unable to retrieve value for '{0}'", key);
            }
        }
        catch (ArgumentNullException)
        {
            Console.WriteLine("Unable to retrieve value for null key.");
        }
    }

    private static string GetConnectionString()
    {
        // To avoid storing the connection string in your code,
        // you can retrieve it from a configuration file.
        return "Server=OracleDemo;Integrated Security=True";
    }
}

' You may need to set a reference to the System.Data.OracleClient
' assembly before you can run this sample.
Imports System.Data.OracleClient

Module Module1
    Sub Main()
        Dim builder As New OracleConnectionStringBuilder()
        builder.ConnectionString = GetConnectionString()

        ' Call TryGetValue method for multiple
        ' key names. Note that these keys are converted
        ' to well-known synonynms for data retrieval.
        DisplayValue(builder, "Data Source")
        DisplayValue(builder, "trusted_connection")
        DisplayValue(builder, "InvalidKey")
        DisplayValue(builder, Nothing)

        Console.WriteLine("Press any key to continue.")
        Console.ReadLine()
    End Sub

    Private Sub DisplayValue( _
     ByVal builder As OracleConnectionStringBuilder, ByVal key As String)
        Dim value As Object = Nothing

        ' Although TryGetValue handles missing keys just fine,
        ' it doesn't handle passing in a null (Nothing in Visual Basic)
        ' key. This example traps for that particular error, but
        ' bubbles any other unknown exceptions back out to the
        ' caller. 
        Try
            If builder.TryGetValue(key, value) Then
                Console.WriteLine("{0}='{1}' ", key, value)
            Else
                Console.WriteLine("Unable to retrieve value for '{0}'", key)
            End If
        Catch ex As ArgumentNullException
            Console.WriteLine("Unable to retrieve value for null key.")
        End Try
    End Sub

    Private Function GetConnectionString() As String
        ' To avoid storing the connection string in your code,
        ' you can retrieve it from a configuration file. 
        Return "Server=OracleDemo;Integrated Security=True"
    End Function
End Module

Commenti

Il TryGetValue metodo consente agli sviluppatori di recuperare in modo sicuro un valore da un OracleConnectionStringBuilder senza dover verificare che il nome della chiave specificato sia un nome di chiave valido. Poiché TryGetValue gestisce in modo corretto la ricerca di una chiave non esistente, non è necessario cercare l'esistenza di una chiave prima di recuperare il relativo valore. La chiamata TryGetValue con una chiave inesistente inserisce il valore Null (Nothing in Visual Basic) nel value parametro .

Vedi anche

• Compilazione delle stringhe di connessione