OracleConnectionStringBuilder.TryGetValue(String, Object) 方法

定义

命名空间:

System.Data.OracleClient

程序集:

System.Data.OracleClient.dll

从此 OracleConnectionStringBuilder 中检索与提供的键相对应的值。

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

参数

keyword

String

要检索的项的键。

value

Object

与 keyword 对应的值。

返回

Boolean

如果在连接字符串中找到 keyword，则为 true；否则为 false。

示例

下面的示例演示 了 方法的行为 TryGetValue 。

// You may need to set a reference to the System.Data.OracleClient
// assembly before you can run this sample.
using System.Data.OracleClient;

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

        // Call TryGetValue method for multiple
        // key names. Note that these keys are converted
        // to well-known synonynms for data retrieval.
        DisplayValue(builder, "Data Source");
        DisplayValue(builder, "Trusted_Connection");
        DisplayValue(builder, "InvalidKey");
        DisplayValue(builder, null);

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

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

        // Although TryGetValue handles missing keys,
        // it does not handle passing in a null
        // key. This example traps for that particular error, but
        // passes 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.");
        }
    }

    private static string GetConnectionString()
    {
        // To avoid storing the connection string in your code,
        // you can retrieve it from a configuration file.
        return "Server=OracleDemo;Integrated Security=True";
    }
}

' You may need to set a reference to the System.Data.OracleClient
' assembly before you can run this sample.
Imports System.Data.OracleClient

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

        ' Call TryGetValue method for multiple
        ' key names. Note that these keys are converted
        ' to well-known synonynms for data retrieval.
        DisplayValue(builder, "Data Source")
        DisplayValue(builder, "trusted_connection")
        DisplayValue(builder, "InvalidKey")
        DisplayValue(builder, Nothing)

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

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

        ' Although TryGetValue handles missing keys just fine,
        ' 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

    Private Function GetConnectionString() As String
        ' To avoid storing the connection string in your code,
        ' you can retrieve it from a configuration file. 
        Return "Server=OracleDemo;Integrated Security=True"
    End Function
End Module

注解

方法 TryGetValue 允许开发人员安全地从 OracleConnectionStringBuilder 检索值，而无需验证提供的密钥名称是否为有效的密钥名称。 由于 TryGetValue 正常处理搜索不存在的键，因此无需在检索其值之前查找键是否存在。 使用不存在的键调用 TryGetValue 会将值 null (Nothing 置于 Visual Basic) 参数中 value 。

另请参阅

• 生成连接字符串