OdbcConnectionStringBuilder.TryGetValue(String, Object) Método

Definição

Namespace:

System.Data.Odbc

Assembly:

System.Data.Odbc.dll

Pacote:

System.Data.Odbc v9.0.0-rc.2.24473.5

Origem:

OdbcConnectionStringbuilder.cs

Recupera um valor correspondente para a chave fornecida deste 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

Parâmetros

keyword

String

A chave do item a ser recuperada.

value

Object

O valor correspondente a keyword.

Retornos

Boolean

true se keyword tiver sido encontrado na cadeia de conexão; caso contrário, false.

Exemplos

O exemplo a seguir demonstra o comportamento do 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

Comentários

O TryGetValue método permite que os desenvolvedores recuperem com segurança um valor de um OdbcConnectionStringBuilder sem a necessidade de verificar se o nome da chave fornecida é um nome de chave válido. Como TryGetValue não gera uma exceção quando você passa uma chave inexistente, você não precisa procurar uma chave antes de recuperar seu valor. Chamar TryGetValue com uma chave inexistente coloca o valor nulo (Nothing no Visual Basic) no value parâmetro .

Confira também

• Construtores de cadeia de conexão
• Cadeias de conexão no ADO.NET