HttpWebRequest.IfModifiedSince プロパティ

.NET Framework クラス ライブラリ リファレンス

HttpWebRequest.IfModifiedSince プロパティ

If-Modified-Since HTTP ヘッダーの値を取得または設定します。

名前空間: System.Net
アセンブリ: System (system.dll 内)
構文

Visual Basic (宣言)

Public Property IfModifiedSince As
 DateTime

Visual Basic (使用法)

Dim instance As HttpWebRequest
Dim value As DateTime

value = instance.IfModifiedSince

instance.IfModifiedSince = value

C#

public DateTime IfModifiedSince { get; set;
 }

C++

public:
property DateTime IfModifiedSince {
    DateTime get ();
    void set (DateTime value);
}

J#

/** @property */
public DateTime get_IfModifiedSince ()

/** @property */
public void set_IfModifiedSince (DateTime value)

JScript

public function get IfModifiedSince
 () : DateTime

public function set IfModifiedSince
 (value : DateTime)

プロパティ値
If-Modified-Since HTTP ヘッダーの内容を格納する DateTime。既定値は、現在の日付と時刻です。

解説

IfModifiedSince プロパティは、現地時間であると想定されます。

メモ
このプロパティの値は WebHeaderCollection に格納されます。WebHeaderCollection が設定されている場合、プロパティ値は失われます。

使用例

IfModifiedSince プロパティをチェックするコード例を次に示します。

Visual Basic

    ' Create a new 'Uri' object with the mentioned string.
    Dim myUri As New Uri("http://www.contoso.com")
    ' Create a new 'HttpWebRequest' object with the above 'Uri' object.
    Dim myHttpWebRequest As HttpWebRequest
 = CType(WebRequest.Create(myUri), HttpWebRequest)
    ' Create a new 'DateTime' object.
    Dim today As DateTime = DateTime.Now
    If DateTime.Compare(today, myHttpWebRequest.IfModifiedSince)
 = 0 Then
        ' Assign the response object of 'HttpWebRequest' to a 'HttpWebResponse'
 variable.
        Dim myHttpWebResponse As HttpWebResponse
 = CType(myHttpWebRequest.GetResponse(), HttpWebResponse)
        Console.WriteLine("Response headers " + ControlChars.Cr
 + "{0}" + ControlChars.Cr, myHttpWebResponse.Headers)
        Dim streamResponse As Stream = myHttpWebResponse.GetResponseStream()
        Dim streamRead As New
 StreamReader(streamResponse)
        Dim readBuff(256) As [Char]
        Dim count As Integer
 = streamRead.Read(readBuff, 0, 256)
        Console.WriteLine(ControlChars.Cr + "The contents of Html
 Page are :  " + ControlChars.Cr)
        While count > 0
            Dim outputData As New
 [String](readBuff, 0, count)
            Console.Write(outputData)
            count = streamRead.Read(readBuff, 0, 256)
        End While
   ' Close the Stream object.
streamResponse.Close()
streamRead.Close()
   ' Release the HttpWebResponse Resource.
myHttpWebResponse.Close()
        Console.WriteLine(ControlChars.Cr + "Press 'Enter' key
 to continue.................")
        Console.Read()
    Else
        Console.WriteLine((ControlChars.Cr + "The page has been
 modified since " + today))
    End If

C#

// Create a new 'Uri' object with the mentioned string.
Uri myUri =new Uri("http://www.contoso.com");
            
// Create a new 'HttpWebRequest' object with the above 'Uri' object.
HttpWebRequest myHttpWebRequest= (HttpWebRequest)WebRequest.Create(myUri);
// Create a new 'DateTime' object.
DateTime today= DateTime.Now;
if (DateTime.Compare(today,myHttpWebRequest.IfModifiedSince)==0)
{
    // Assign the response object of 'HttpWebRequest' to a 'HttpWebResponse'
 variable.
    HttpWebResponse myHttpWebResponse=(HttpWebResponse)myHttpWebRequest.GetResponse();
    Console.WriteLine("Response headers \n{0}\n",myHttpWebResponse.Headers);
    Stream streamResponse=myHttpWebResponse.GetResponseStream();
    StreamReader streamRead = new StreamReader( streamResponse
 );
    Char[] readBuff = new Char[256];
    int count = streamRead.Read( readBuff, 0, 256 );
    Console.WriteLine("\nThe contents of Html Page are :  \n");    
    while (count > 0) 
    {
        String outputData = new String(readBuff, 0, count);
        Console.Write(outputData);
        count = streamRead.Read(readBuff, 0, 256);
    }
    // Close the Stream object.
    streamResponse.Close();
    streamRead.Close();
    // Release the HttpWebResponse Resource.
    myHttpWebResponse.Close();
    Console.WriteLine("\nPress 'Enter' key to continue.................");
    
    Console.Read();
}
else
{
    Console.WriteLine("\nThe page has been modified since "+today);
}

C++

      // Create a new 'Uri' object with the mentioned string.
      Uri^ myUri = gcnew Uri( "http://www.contoso.com" );
      
      // Create a new 'HttpWebRequest' object with the above 'Uri' object.
      HttpWebRequest^ myHttpWebRequest = dynamic_cast<HttpWebRequest^>(WebRequest::Create(
 myUri ));
      
      // Create a new 'DateTime' object.
      DateTime today = DateTime::Now;
      if ( DateTime::Compare( today, myHttpWebRequest->IfModifiedSince
 ) == 0 )
      {
         
         // Assign the response object of 'HttpWebRequest' to a 'HttpWebResponse'
 variable.
         HttpWebResponse^ myHttpWebResponse = dynamic_cast<HttpWebResponse^>(myHttpWebRequest->GetResponse());
         Console::WriteLine( "Response headers \n {0}\n", myHttpWebResponse->Headers
 );
         Stream^ streamResponse = myHttpWebResponse->GetResponseStream();
         StreamReader^ streamRead = gcnew StreamReader( streamResponse );
         array<Char>^readBuff = gcnew array<Char>(256);
         int count = streamRead->Read( readBuff, 0, 256 );
         Console::WriteLine( "\nThe contents of Html Page are :  \n" );
         while ( count > 0 )
         {
            String^ outputData = gcnew String( readBuff,0,count );
            Console::Write( outputData );
            count = streamRead->Read( readBuff, 0, 256 );
         }
         streamResponse->Close();
         streamRead->Close();
         
         // Release the HttpWebResponse Resource.
         myHttpWebResponse->Close();
         Console::WriteLine( "\nPress 'Enter' key to continue................."
 );
         Console::Read();
      }
      else
      {
         Console::WriteLine( "\nThe page has been modified since {0}",
 today );
      }
   }
   catch ( WebException^ e ) 
   {
      Console::WriteLine( "\nWebException Caught!" );
      Console::WriteLine( "Source  : {0}", e->Source );
      Console::WriteLine( "Message : {0}", e->Message );
   }
   catch ( Exception^ e ) 
   {
      Console::WriteLine( "\nException raised!" );
      Console::WriteLine( "Source  : {0}", e->Source );
      Console::WriteLine( "Message : {0}", e->Message );
   }

}

J#

// Create a new 'Uri' object with the mentioned string.
Uri myUri = new Uri("http://www.contoso.com");

//Create a new 'HttpWebRequest' object with the above 'Uri' object.
HttpWebRequest myHttpWebRequest = (HttpWebRequest)
    (WebRequest.Create(myUri));
// Create a new 'DateTime' object.
DateTime today = DateTime.get_Now();

if (DateTime.Compare(today, 
    myHttpWebRequest.get_IfModifiedSince()) == 0) {
    // Assign the response object of 'HttpWebRequest' to a 
    //    'HttpWebResponse' variable.
    HttpWebResponse myHttpWebResponse = (HttpWebResponse)
        (myHttpWebRequest.GetResponse());
    Console.WriteLine("Response headers \n{0}\n", 
        myHttpWebResponse.get_Headers());
    Stream streamResponse = myHttpWebResponse.GetResponseStream();
    StreamReader streamRead = new StreamReader(streamResponse);
    char readBuff[] = new char[256];
    int count = streamRead.Read(readBuff, 0, 256);
    Console.WriteLine("\nThe contents of Html Page are :  \n");
    while (count > 0) {
        String outputData = new String(readBuff, 0, count);
        Console.Write(outputData);
        count = streamRead.Read(readBuff, 0, 256);
    }
    // Close the Stream object.
    streamResponse.Close();
    streamRead.Close();
    // Release the HttpWebResponse Resource.
    myHttpWebResponse.Close();
    Console.WriteLine("\nPress 'Enter' key to continue"
        + ".................");
    Console.Read();
}
else {
    Console.WriteLine("\nThe page has been modified since "
        + today);
}

プラットフォーム

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
HttpWebRequest クラス
HttpWebRequest メンバ
System.Net 名前空間