DbConnectionStringBuilder.TryGetValue(String, Object) Method

Definition

Retrieves a value corresponding to the supplied key from this DbConnectionStringBuilder.

public:
 virtual bool TryGetValue(System::String ^ keyword, [Runtime::InteropServices::Out] System::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

Parameters

keyword
String

The key of the item to retrieve.

value
Object

The value corresponding to the keyword.

Returns

true if keyword was found within the connection string, false otherwise.

Exceptions

keyword contains a null value (Nothing in Visual Basic).

Examples

The following example calls the TryGetValue method, demonstrating several possible outcomes.

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

The sample displays the following results:

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

Remarks

The TryGetValue method lets developers safely retrieve a value from a DbConnectionStringBuilder without needing to first call the ContainsKey method. Because TryGetValue does not raise an exception when you call it, passing in a nonexistent key, you do not have to look for a key before retrieving its value. Calling TryGetValue with a nonexistent key will place the null value (Nothing in Visual Basic) in the value parameter.

Applies to

See also