SqlConnectionStringBuilder.TryGetValue(String, Object) 方法

定義

命名空間:

System.Data.SqlClient

組件:

System.Data.SqlClient.dll

套件:

System.Data.SqlClient v4.8.6

從這個 SqlConnectionStringBuilder 擷取對應到所提供之索引鍵的值。

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

參數

keyword

String

要擷取之項目的索引鍵。

value

Object

對應到 keyword 的值。

傳回

Boolean

如果在連接字串中找到 keyword，則為 true；否則為 false。

例外狀況

ArgumentNullException

keyword 包含 null 值 (在 Visual Basic 中為 Nothing)。

範例

下列範例示範 TryGetValue 方法的行為。

using System.Data.SqlClient;

using System;
using System.Data.SqlClient;

class Program
{
    static void Main()
    {
        SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder();
        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(
        SqlConnectionStringBuilder 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
        // 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=(local);Integrated Security=SSPI;" +
            "Initial Catalog=AdventureWorks";
    }
}

Imports System.Data.SqlClient
    
Module Module1
    Sub Main()
        Dim builder As New SqlConnectionStringBuilder
        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 SqlConnectionStringBuilder, ByVal key As String)
        Dim value As Object = Nothing

        ' 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
        ' passes 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=(local);Integrated Security=SSPI;" & _
          "Initial Catalog=AdventureWorks"
    End Function
End Module

此範例會顯示下列結果：

Data Source=(local)
Trusted_Connection=True
Unable to retrieve value for 'InvalidKey'
Unable to retrieve value for null key.

備註

TryGetValue 方法可讓開發人員安全地從 SqlConnectionStringBuilder 擷取值，而不需確認提供的索引鍵名稱是有效的索引鍵名稱。 因為 TryGetValue 不會在呼叫時引發例外狀況，傳入不存在的索引鍵，所以您不需要在擷取其值之前尋找索引鍵。 使用不存在的索引鍵呼叫 TryGetValue 會將 (Nothing null 值放在 Visual Basic) 參數中 value 。

另請參閱

• ADO.NET 中的連接字串
• ADO.NET 概觀 \(部分機器翻譯\)