SqlConnectionStringBuilder.TryGetValue(String, Object) 方法

定義

命名空間:

Microsoft.Data.SqlClient

組件:

Microsoft.Data.SqlClient.dll

套件:

Microsoft.Data.SqlClient v5.2.0

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 Microsoft.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";
    }
}

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先尋找索引鍵。 呼叫具有不存在索引鍵的TryGetValue會將 null 值放在 參數的 value Visual Basic () Nothing 中。