OdbcConnectionStringBuilder.TryGetValue(String, Object) Método

Definición

Espacio de nombres:

System.Data.Odbc

Ensamblado:

System.Data.Odbc.dll

Paquete:

System.Data.Odbc v8.0.0

Source:

OdbcConnectionStringbuilder.cs

Recupera un valor que corresponde a la clave proporcionada por este OdbcConnectionStringBuilder.

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

Parámetros

keyword

String

Clave del elemento que se va a recuperar.

value

Object

Valor que corresponde a keyword.

Devoluciones

Boolean

true si se encuentra keyword en la cadena de conexión; de lo contrario, false.

Ejemplos

En el ejemplo siguiente se muestra el comportamiento del TryGetValue método .

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

Comentarios

El método TryGetValue permite a los programadores recuperar de manera segura un valor de OdbcConnectionStringBuilder sin tener que comprobar si el nombre de clave proporcionado es válido. Dado TryGetValue que no genera una excepción cuando se pasa una clave inexistente, no es necesario buscar una clave antes de recuperar su valor. Al llamar a TryGetValue con una clave inexistente, se coloca el valor NULL (Nothing en Visual Basic) en el value parámetro .

Consulte también

• Generadores de cadenas de conexión
• Cadenas de conexión de ADO.NET