DbConnectionStringBuilder.TryGetValue(String, Object) Metode

  • Referensi

Definisi

Ruang nama:
System.Data.Common
Rakitan:
System.Data.Common.dll
Rakitan:
System.Data.dll
Rakitan:
netstandard.dll
Sumber:
DbConnectionStringBuilder.cs
Sumber:
DbConnectionStringBuilder.cs
Sumber:
DbConnectionStringBuilder.cs

Mengambil nilai yang sesuai dengan kunci yang disediakan dari ini DbConnectionStringBuilder.

public:
 virtual bool TryGetValue(System::String ^ keyword, [Runtime::InteropServices::Out] System::Object ^ % value);
public virtual bool TryGetValue (string keyword, out object value);
public virtual bool TryGetValue (string keyword, out object? value);
abstract member TryGetValue : string * obj -> bool
override this.TryGetValue : string * obj -> bool
Public Overridable Function TryGetValue (keyword As String, ByRef value As Object) As Boolean

Parameter

keyword
String

Kunci item yang akan diambil.

value
Object

Nilai yang keywordsesuai dengan .

Mengembalikan

Boolean

truejika keyword ditemukan dalam string koneksi, false jika tidak.

Pengecualian

ArgumentNullException

keyword berisi nilai null (Nothing dalam Visual Basic).

Contoh

Contoh berikut memanggil TryGetValue metode , menunjukkan beberapa kemungkinan hasil.

static void Main()
{
    DbConnectionStringBuilder builder = new DbConnectionStringBuilder();
    builder.ConnectionString =
        "Provider=sqloledb;Data Source=192.168.168.1,1433;" +
        "Network Library=DBMSSOCN;Initial Catalog=pubs;" +
        "Integrated Security=SSPI;";

    // Call TryGetValue method for multiple
    // key names.
    DisplayValue(builder, "Provider");
    DisplayValue(builder, "DATA SOURCE");
    DisplayValue(builder, "InvalidKey");
    DisplayValue(builder, null);

    Console.ReadLine();
}

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

    // Although TryGetValue handles missing keys,
    // it doesn't handle passing in a null
    // key. This example traps for that particular error, but
    // bubbles 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.");
    }
}

Sub Main()
    Dim builder As New DbConnectionStringBuilder
    builder.ConnectionString = _
        "Provider=sqloledb;Data Source=192.168.168.1,1433;" & _
        "Network Library=DBMSSOCN;Initial Catalog=pubs;" & _
        "Integrated Security=SSPI;"

    ' Call TryGetValue method for multiple
    ' key names.
    DisplayValue(builder, "Provider")
    DisplayValue(builder, "DATA SOURCE")
    DisplayValue(builder, "InvalidKey")
    DisplayValue(builder, Nothing)

    Console.ReadLine()
End Sub

Private Sub DisplayValue( _
 ByVal builder As DbConnectionStringBuilder, ByVal key As String)
    Dim value As Object

    ' Although TryGetValue handles missing keys,
    ' 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

Sampel menampilkan hasil berikut:

Provider=sqloledb
DATA SOURCE=192.168.168.1,1433
Unable to retrieve value for //InvalidKey//
Unable to retrieve value for null key.

Keterangan

Metode ini TryGetValue memungkinkan pengembang mengambil nilai dengan aman dari DbConnectionStringBuilder tanpa perlu terlebih dahulu memanggil metode .ContainsKey Karena TryGetValue tidak menimbulkan pengecualian saat Anda memanggilnya, meneruskan kunci yang tidak ada, Anda tidak perlu mencari kunci sebelum mengambil nilainya. Memanggil TryGetValue dengan kunci yang tidak ada akan menempatkan nilai null (Nothing di Visual Basic) dalam value parameter .

Berlaku untuk

Lihat juga