DbConnectionStringBuilder.TryGetValue(String, Object) 方法

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

參數

傳回

如果在連接字串中找到 keyword，則為 true；否則為 false。

例外狀況

範例

下列範例會呼叫 TryGetValue 方法，示範數個可能的結果。

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

此範例會顯示下列結果：

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

備註

方法 TryGetValue 可讓開發人員安全地從 擷取值， DbConnectionStringBuilder 而不需要先呼叫 ContainsKey 方法。 因為 TryGetValue 當您呼叫它時不會引發例外狀況，所以傳入不存在的索引鍵時，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 null 值 (放在 Nothing Visual Basic) 參數中 value 。

適用於

另請參閱

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