OleDbConnectionStringBuilder.TryGetValue(String, Object) Yöntem

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

Parametreler

Döndürülenler

truebağlantı dizesi içinde bulunduysa; bulunamazsakeyword, false.

Özel durumlar

Örnekler

Aşağıdaki örnekte yönteminin davranışı gösterilmektedir TryGetValue .

using System.Data.OleDb;

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

        // Call TryGetValue method for multiple
        // key names.
        DisplayValue(builder, "Data Source");
        DisplayValue(builder, "Extended Properties");
        // How about implicitly added key/value pairs?
        DisplayValue(builder, "Jet OLEDB:System database");
        // Invalid keys?
        DisplayValue(builder, "Invalid Key");
        // Null values?
        DisplayValue(builder, null);

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

    static private void DisplayValue(OleDbConnectionStringBuilder 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)
        {
            Console.WriteLine("Unable to retrieve value for null key.");
        }
    }

    static private 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 "Provider=Microsoft.Jet.OLEDB.4.0;" +
            "Data Source=C:\\ExcelDemo.xls;" +
            "Extended Properties=\"Excel 8.0;HDR=Yes;IMEX=1\"";
    }
}

Imports System.Data.OleDb    

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

    ' Call TryGetValue method for multiple
    ' key names. 
    DisplayValue(builder, "Data Source")
    DisplayValue(builder, "Extended Properties")
    ' How about implicitly added key/value pairs?
    DisplayValue(builder, "Jet OLEDB:System database")
    ' 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 OleDbConnectionStringBuilder, 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 "Provider=Microsoft.Jet.OLEDB.4.0;" & _
      "Data Source=C:\ExcelDemo.xls;" & _
      "Extended Properties=""Excel 8.0;HDR=Yes;IMEX=1"""
  End Function
End Module

Açıklamalar

TryGetValue yöntemi, geliştiricilerin sağlanan anahtar adının geçerli bir anahtar adı olduğunu doğrulamaya gerek kalmadan değerinden bir değeri OleDbConnectionStringBuilder güvenli bir şekilde almasını sağlar. TryGetValue Çağırdığınızda, var olmayan bir anahtar geçirerek özel durum oluşturmadığından, değerini almadan önce bir anahtar aramanız gerekmez. Var olmayan bir anahtarla çağırmak TryGetValue , null değerini (Nothing Visual Basic'te) parametresine value yerleştirir.

Şunlara uygulanır

Ayrıca bkz.

• Bağlantı Dizesi Oluşturucular
• ADO.NET'da Bağlantı Dizeleri