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OdbcConnectionStringBuilder.TryGetValue(String, Object) Methode

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Definition

Namespace:
System.Data.Odbc
Assembly:
System.Data.Odbc.dll
Assembly:
System.Data.dll
Paket:
System.Data.Odbc v8.0.1
Paket:
System.Data.Odbc v9.0.0-rc.2.24473.5
Quelle:
OdbcConnectionStringbuilder.cs
Quelle:
OdbcConnectionStringbuilder.cs

Ruft einen Wert ab, der dem von diesem OdbcConnectionStringBuilder bereitgestellten Schlüssel entspricht.

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

Parameter

keyword
String

Der Schlüssel des abzurufenden Elements.

value
Object

Der Wert, der keyword entspricht.

Gibt zurück

Boolean

true, wenn keyword in der Verbindungszeichenfolge gefunden wurde, andernfalls false.

Beispiele

Im folgenden Beispiel wird das Verhalten der TryGetValue -Methode veranschaulicht.

using System.Data.Odbc;

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

        // Call TryGetValue method for multiple
        // key names. Demonstrate that the search is not
        // case sensitive.
        DisplayValue(builder, "Driver");
        DisplayValue(builder, "SERVER");
        // How about a property you did not set?
        DisplayValue(builder, "DNS");
        // Invalid keys?
        DisplayValue(builder, "Invalid Key");
        // Null values?
        DisplayValue(builder, null);

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

    private static string GetConnectionString()
    {
        // To avoid storing the connection string in your code,
        // you can retrieve it from a configuration file using the
        // System.Configuration.ConfigurationSettings.AppSettings property.
        return "Driver={SQL Server};Server=(local);" +
            "Database=AdventureWorks;Trusted_Connection=yes;";
    }

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

        // Although TryGetValue handles missing keys,
        // it does not handle passing in a null (Nothing in Visual Basic)
        // key. This example traps for that particular error, but
        // throws 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 ex)
        {
            Console.WriteLine("Unable to retrieve value for null key.");
        }
    }
}

Imports System.Data.Odbc
    
Module Module1

  Sub Main()
    Dim builder As New OdbcConnectionStringBuilder
    builder.ConnectionString = GetConnectionString()

    ' Call TryGetValue method for multiple
    ' key names. Demonstrate that the search is not
    ' case sensitive.
    DisplayValue(builder, "Driver")
    DisplayValue(builder, "SERVER")
    ' How about a property you did not set?
    DisplayValue(builder, "DNS")
    ' Invalid keys?
    DisplayValue(builder, "Invalid Key")
    ' Null values?
    DisplayValue(builder, Nothing)

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

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

    ' Although TryGetValue handles missing keys,
    ' it does not handle passing in a null (Nothing in Visual Basic)
    ' key. This example traps for that particular error, but
    ' throws 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 using the 
    ' System.Configuration.ConfigurationSettings.AppSettings property. 
    Return "Driver={SQL Server};Server=(local);" & _
      "Database=AdventureWorks;Trusted_Connection=yes;"
  End Function
End Module

Hinweise

Mit der TryGetValue-Methode können Entwickler einen Wert sicher aus einem OdbcConnectionStringBuilder abrufen, ohne die Gültigkeit des bereitgestellten Schlüsselnamens überprüfen zu müssen. Da TryGetValue keine Ausnahme ausgelöst wird, wenn Sie einen nicht vorhandenen Schlüssel übergeben, müssen Sie vor dem Abrufen des Werts nicht nach einem Schlüssel suchen. Beim Aufrufen TryGetValue mit einem nicht vorhandenen Schlüssel wird der Wert NULL (Nothing in Visual Basic) im value Parameter platziert.

Gilt für:

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