DetailsViewUpdateEventHandler デリゲートとは何？わかりやすく解説 Weblio辞書

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DetailsViewUpdateEventHandler デリゲート

メモ : このデリゲートは、.NET Framework version 2.0 で新しく追加されたものです。

DetailsView コントロールの ItemUpdating イベントを処理するメソッドを表します。

名前空間: System.Web.UI.WebControls
アセンブリ: System.Web (system.web.dll 内)
構文

Visual Basic (宣言)

Public Delegate Sub DetailsViewUpdateEventHandler
 ( _
    sender As Object, _
    e As DetailsViewUpdateEventArgs _
)

Visual Basic (使用法)

Dim instance As New DetailsViewUpdateEventHandler(AddressOf
 HandlerMethod)

public delegate void DetailsViewUpdateEventHandler
 (
    Object sender,
    DetailsViewUpdateEventArgs e
)

C++

public delegate void DetailsViewUpdateEventHandler
 (
    Object^ sender, 
    DetailsViewUpdateEventArgs^ e
)

/** @delegate */
public delegate void DetailsViewUpdateEventHandler
 (
    Object sender, 
    DetailsViewUpdateEventArgs e
)

JScript

JScript では、デリゲートは使用できますが、新規に宣言することはできません。

パラメータ

sender: イベントのソース。

e: イベントデータを格納している DetailsViewUpdateEventArgs。

解説

DetailsView コントロールは、コントロール内の Update ボタン (CommandName プロパティが "Update" に設定されたボタン) がクリックされた場合に、DetailsView コントロールが実際にレコードを更新する前に ItemUpdating イベントを発生させます。これにより、このイベントが発生するたびにカスタムルーチン (データソースでレコードを更新する前にレコードの値を HTML エンコーディングするなど) を実行するイベントハンドラを提供できます。

DetailsViewUpdateEventHandler デリゲートを作成する場合は、イベントを処理するメソッドを識別してください。イベントをイベントハンドラに関連付けるには、デリゲートのインスタンスをイベントに追加します。デリゲートを削除しない限り、そのイベントが発生すると常にイベントハンドラが呼び出されます。イベントハンドラデリゲートの詳細については、「イベントとデリゲート」を参照してください。

使用例

DetailsViewUpdateEventHandler デリゲートを、プログラムによって DetailsView コントロールの ItemUpdating イベントに追加する方法のコード例を次に示します。

Visual Basic

<%@ Page language="VB" %>

<script runat="server">
  
  Sub Page_Load(ByVal sender As
 Object, ByVal e As EventArgs)
    
    ' Create a new DetailsView object.
    Dim customerDetailsView As New
 DetailsView()

    ' Set the DetailsView object's properties.
    customerDetailsView.ID = "CustomerDetailsView"
    customerDetailsView.DataSourceID = "DetailsViewSource"
    customerDetailsView.AutoGenerateRows = True
    customerDetailsView.AutoGenerateEditButton = True
    customerDetailsView.AllowPaging = True
    customerDetailsView.PagerSettings.Position = PagerPosition.Bottom

    Dim keyArray() As String
 = {"CustomerID"}
    customerDetailsView.DataKeyNames = keyArray
    
    ' Programmatically register the event-handling methods
    ' for the DetailsView control.
    AddHandler customerDetailsView.ItemUpdating, _
      AddressOf CustomerDetailsView_ItemUpdating
    AddHandler customerDetailsView.ModeChanging, _
      AddressOf CustomerDetailsView_ModeChanging

    ' Add the DetailsView object to the Controls collection
    ' of the PlaceHolder control.
    DetailsViewPlaceHolder.Controls.Add(customerDetailsView)

  End Sub
  
  Sub CustomerDetailsView_ItemUpdating(ByVal
 sender As Object, _
    ByVal e As DetailsViewUpdateEventArgs)

    ' Validate the field values entered by the user. This
    ' example determines whether the user left any fields
    ' empty. Use the NewValues property to access the new 
    ' values entered by the user.
    Dim emptyFieldList As ArrayList = _
      ValidateFields(CType(e.NewValues, IOrderedDictionary))

    If emptyFieldList.Count > 0 Then

      ' The user left some fields empty. Display an error message.
      
      ' Use the Keys property to retrieve the key field value.
      Dim keyValue As String
 = e.Keys("CustomerID").ToString()

      MessageLabel.Text = _
        "You must enter a value for all fields of record "
 & _
        keyValue & ".<br/>The following fields are missing:<br/><br/>"

      ' Display the missing fields.
      Dim value As String
      For Each value In
 emptyFieldList
      
        ' Use the OldValues property access the original value
        ' of a field.
        MessageLabel.Text &= value & " - Original Value
 = " & _
          e.OldValues(value).ToString() & "<br>"
        
      Next

      ' Cancel the update operation.
      e.Cancel = True

    Else
    
      ' The field values passed validation. Clear the
      ' error message label.
      MessageLabel.Text = ""
      
    End If

  End Sub

    Function ValidateFields(ByVal list As
 IOrderedDictionary) _
      As ArrayList
    
        ' Create an ArrayList object to store the
        ' names of any empty fields.
        Dim emptyFieldList As New
 ArrayList()

        ' Iterate though the field values entered by
        ' the user and check for an empty field. Empty
        ' fields contain a null value.
        Dim entry As DictionaryEntry
    
        For Each entry In
 list
    
            If entry.Value Is Nothing
 Then
      
                ' Add the field name to the ArrayList object.
                emptyFieldList.Add(entry.Key.ToString())
        
            End If
        Next

        Return emptyFieldList
  
    End Function

  Sub CustomerDetailsView_ModeChanging(ByVal
 sender As Object, ByVal
 e As DetailsViewModeEventArgs)
  
    If e.CancelingEdit Then
      
      ' The user canceled the update operation.
      ' Clear the error message label.
      MessageLabel.Text = ""
    
    End If
    
  End Sub

</script>

<html>
  <body>
    <form runat="server">
        
      <h3>DetailsViewUpdateEventHandler Example</h3>
        
      <!-- Use a PlaceHolder control as the container for
 the -->
      <!-- dynamically generated DetailsView control.         -->       
      <asp:placeholder id="DetailsViewPlaceHolder"
        runat="server"/>
        
      <br/><br/>
      
      <asp:label id="MessageLabel"
        forecolor="Red"
        runat="server"/>
          
      <!-- This example uses Microsoft SQL Server and connects
  -->
      <!-- to the Northwind sample database. Use an ASP.NET
     -->
      <!-- expression to retrieve the connection string
 value   -->
      <!-- from the web.config file.                            -->
      <asp:sqldatasource id="DetailsViewSource"
        selectcommand="Select [CustomerID], [CompanyName], [Address], 
          [City], [PostalCode], [Country] From [Customers]"
        updatecommand="Update [Customers] Set 
          [CompanyName]=@CompanyName, [Address]=@Address, 
          [City]=@City, [PostalCode]=@PostalCode, 
          [Country]=@Country Where [CustomerID]=@CustomerID"
        connectionstring=
          "<%$ ConnectionStrings:NorthWindConnectionString%>"
 
        runat="server"/>
s    </form>
  </body>
</html>

<%@ Page language="C#" %>

<script runat="server">
  
  void Page_Load(Object sender, EventArgs e)
  {

    // Create a new DetailsView object.
    DetailsView customerDetailsView = new DetailsView();

    // Set the DetailsView object's properties.
    customerDetailsView.ID = "CustomerDetailsView";
    customerDetailsView.DataSourceID = "DetailsViewSource";
    customerDetailsView.AutoGenerateRows = true;
    customerDetailsView.AutoGenerateEditButton = true;
    customerDetailsView.AllowPaging = true;
    customerDetailsView.DataKeyNames = new String[1] { "CustomerID"
 };
    customerDetailsView.PagerSettings.Position = PagerPosition.Bottom;

    // Programmatically register the event-handling methods
    // for the DetailsView control.
    customerDetailsView.ItemUpdating 
      += new DetailsViewUpdateEventHandler(
      this.CustomerDetailsView_ItemUpdating);
    customerDetailsView.ModeChanging 
      += new DetailsViewModeEventHandler(
      this.CustomerDetailsView_ModeChanging);

    // Add the DetailsView object to the Controls collection
    // of the PlaceHolder control.
    DetailsViewPlaceHolder.Controls.Add(customerDetailsView);

  }
  
  void CustomerDetailsView_ItemUpdating(Object sender, 
    DetailsViewUpdateEventArgs e)
  {

    // Validate the field values entered by the user. This
    // example determines whether the user left any fields
    // empty. Use the NewValues property to access the new 
    // values entered by the user.
    ArrayList emptyFieldList = 
      ValidateFields((IOrderedDictionary)e.NewValues);

    if (emptyFieldList.Count > 0)
    {

      // The user left some fields empty. Display an error message.
      
      // Use the Keys property to retrieve the key field value.
      String keyValue = e.Keys["CustomerID"].ToString();

      MessageLabel.Text = 
        "You must enter a value for all fields of record
 " +
        keyValue + ".<br/>The following fields are missing:<br/><br/>";

      // Display the missing fields.
      foreach (String value in emptyFieldList)
      {
        // Use the OldValues property access the original value
        // of a field.
        MessageLabel.Text += value + " - Original Value = " + 
          e.OldValues[value].ToString() + "<br>";
      }

      // Cancel the update operation.
      e.Cancel = true;

    }
    else
    {
      // The field values passed validation. Clear the
      // error message label.
      MessageLabel.Text = "";
    }

  }

  ArrayList ValidateFields(IOrderedDictionary list)
  {
    
    // Create an ArrayList object to store the
    // names of any empty fields.
    ArrayList emptyFieldList = new ArrayList();

    // Iterate though the field values entered by
    // the user and check for an empty field. Empty
    // fields contain a null value.
    foreach (DictionaryEntry entry in list)
    {
      if (entry.Value == null)
      {
        // Add the field name to the ArrayList object.
        emptyFieldList.Add(entry.Key.ToString());
      }
    }

    return emptyFieldList;
  }

  void CustomerDetailsView_ModeChanging(Object sender, 
    DetailsViewModeEventArgs e)
  {
    if (e.CancelingEdit)
    {
      // The user canceled the update operation.
      // Clear the error message label.
      MessageLabel.Text = "";
    }
  }

</script>

<html>
  <body>
    <form runat="server">
        
      <h3>DetailsViewUpdateEventHandler Example</h3>
        
      <!-- Use a PlaceHolder control as the container for the
 -->
      <!-- dynamically generated DetailsView control.         -->       
      <asp:placeholder id="DetailsViewPlaceHolder"
        runat="server"/>
        
      <br/><br/>
      
      <asp:label id="MessageLabel"
        forecolor="Red"
        runat="server"/>
          
      <!-- This example uses Microsoft SQL Server and connects  -->
      <!-- to the Northwind sample database. Use an ASP.NET     -->
      <!-- expression to retrieve the connection string value
   -->
      <!-- from the web.config file.                            -->
      <asp:sqldatasource id="DetailsViewSource"
        selectcommand="Select [CustomerID], [CompanyName], [Address], 
          [City], [PostalCode], [Country] From [Customers]"
        updatecommand="Update [Customers] Set 
          [CompanyName]=@CompanyName, [Address]=@Address, 
          [City]=@City, [PostalCode]=@PostalCode, 
          [Country]=@Country 
          Where [CustomerID]=@CustomerID"
        connectionstring=
          "<%$ ConnectionStrings:NorthWindConnectionString%>" 
        runat="server"/>
          
    </form>
  </body>
</html>

DetailsViewUpdateEventHandler デリゲートを、宣言によって DetailsView コントロールの ItemUpdating イベントに追加する方法のコード例を次に示します。

Visual Basic

<%@ Page language="VB" autoeventwireup="false"
 %>

<script runat="server">
  
  Sub CustomerDetailsView_ItemUpdating(ByVal
 sender As Object, ByVal
 e As DetailsViewUpdateEventArgs) Handles CustomerDetailsView.ItemUpdating

    ' Validate the field values entered by the user. This
    ' example determines whether the user left any fields
    ' empty. Use the NewValues property to access the new 
    ' values entered by the user.
        Dim emptyFieldList As ArrayList = ValidateFields(CType(e.NewValues,
 IOrderedDictionary))

    If emptyFieldList.Count > 0 Then

      ' The user left some fields empty. Display an error message.
      
      ' Use the Keys property to retrieve the key field value.
      Dim keyValue As String
 = e.Keys("CustomerID").ToString()

      MessageLabel.Text = "You must enter a value for all fields
 of record " & _
        keyValue & ".<br/>The following fields are missing:<br/><br/>"

      ' Display the missing fields.
      Dim value As String
      For Each value In
 emptyFieldList
      
        ' Use the OldValues property access the original value
        ' of a field.
        MessageLabel.Text &= value & " - Original Value
 = " & _
          e.OldValues(value).ToString() & "<br>"
        
      Next

      ' Cancel the update operation.
      e.Cancel = True

    Else
    
      ' The field values passed validation. Clear the
      ' error message label.
      MessageLabel.Text = ""
      
    End If

  End Sub

    Function ValidateFields(ByVal list As
 IOrderedDictionary) As ArrayList
    
        ' Create an ArrayList object to store the
        ' names of any empty fields.
        Dim emptyFieldList As New
 ArrayList()

        ' Iterate though the field values entered by
        ' the user and check for an empty field. Empty
        ' fields contain a null value.
        Dim entry As DictionaryEntry
    
        For Each entry In
 list
    
            If entry.Value Is Nothing
 Then
      
                ' Add the field name to the ArrayList object.
                emptyFieldList.Add(entry.Key.ToString())
        
            End If
        Next

        Return emptyFieldList
  
    End Function

  Sub CustomerDetailsView_ModeChanging(ByVal
 sender As Object, ByVal
 e As DetailsViewModeEventArgs) Handles CustomerDetailsView.ModeChanging
  
    If e.CancelingEdit Then
      
      ' The user canceled the update operation.
      ' Clear the error message label.
      MessageLabel.Text = ""
    
    End If
    
  End Sub

</script>

<html>
  <body>
    <form runat="server">
        
      <h3>DetailsViewUpdateEventHandler Example</h3>
                       
      <asp:detailsview id="CustomerDetailsView"
        datasourceid="DetailsViewSource"
        autogeneraterows="true"
        autogenerateeditbutton="true"  
        allowpaging="true"
        datakeynames="CustomerID" 
        runat="server">
          
        <pagersettings position="Bottom"/> 
                  
      </asp:detailsview>
      
      <br/>
      
      <asp:label id="MessageLabel"
        forecolor="Red"
        runat="server"/>
          
      <!-- This example uses Microsoft SQL Server and connects
  -->
      <!-- to the Northwind sample database. Use an ASP.NET
     -->
      <!-- expression to retrieve the connection string
 value   -->
      <!-- from the web.config file.                            -->
      <asp:sqldatasource id="DetailsViewSource"
        selectcommand="Select [CustomerID], [CompanyName], [Address], 
          [City], [PostalCode], [Country] From [Customers]"
        updatecommand="Update [Customers] Set 
          [CompanyName]=@CompanyName, [Address]=@Address, 
          [City]=@City, [PostalCode]=@PostalCode, 
          [Country]=@Country 
          Where [CustomerID]=@CustomerID"
        connectionstring=
          "<%$ ConnectionStrings:NorthWindConnectionString%>"
 
        runat="server"/>
          
    </form>
  </body>
</html>

<%@ Page language="C#" %>

<script runat="server">
  
  void CustomerDetailsView_ItemUpdating(Object sender, 
    DetailsViewUpdateEventArgs e)
  {

    // Validate the field values entered by the user. This
    // example determines whether the user left any fields
    // empty. Use the NewValues property to access the new 
    // values entered by the user.
    ArrayList emptyFieldList = 
      ValidateFields((IOrderedDictionary)e.NewValues);

    if (emptyFieldList.Count > 0)
    {

      // The user left some fields empty. Display an error message.
      
      // Use the Keys property to retrieve the key field value.
      String keyValue = e.Keys["CustomerID"].ToString();

      MessageLabel.Text = 
        "You must enter a value for all fields of record
 " +
        keyValue + ".<br/>The following fields are missing:<br/><br/>";

      // Display the missing fields.
      foreach (String value in emptyFieldList)
      {
        // Use the OldValues property access the original value
        // of a field.
        MessageLabel.Text += value + " - Original Value = " + 
          e.OldValues[value].ToString() + "<br>";
      }

      // Cancel the update operation.
      e.Cancel = true;

    }
    else
    {
      // The field values passed validation. Clear the
      // error message label.
      MessageLabel.Text = "";
    }

  }

  ArrayList ValidateFields(IOrderedDictionary list)
  {
    
    // Create an ArrayList object to store the
    // names of any empty fields.
    ArrayList emptyFieldList = new ArrayList();

    // Iterate though the field values entered by
    // the user and check for an empty field. Empty
    // fields contain a null value.
    foreach (DictionaryEntry entry in list)
    {
      if (entry.Value == null)
      {
        // Add the field name to the ArrayList object.
        emptyFieldList.Add(entry.Key.ToString());
      }
    }

    return emptyFieldList;
  }

  void CustomerDetailsView_ModeChanging(Object sender, 
    DetailsViewModeEventArgs e)
  {
    if (e.CancelingEdit)
    {
      // The user canceled the update operation.
      // Clear the error message label.
      MessageLabel.Text = "";
    }
  }

</script>

<html>
  <body>
    <form runat="server">
        
      <h3>DetailsViewUpdateEventHandler Example</h3>
                       
      <asp:detailsview id="CustomerDetailsView"
        datasourceid="DetailsViewSource"
        autogeneraterows="true"
        autogenerateeditbutton="true"  
        allowpaging="true"
        datakeynames="CustomerID" 
        onitemupdating="CustomerDetailsView_ItemUpdating"
        onmodechanging="CustomerDetailsView_ModeChanging" 
        runat="server">
          
        <pagersettings position="Bottom"/> 
                  
      </asp:detailsview>
      
      <br/>
      
      <asp:label id="MessageLabel"
        forecolor="Red"
        runat="server"/>
          
      <!-- This example uses Microsoft SQL Server and connects  -->
      <!-- to the Northwind sample database. Use an ASP.NET     -->
      <!-- expression to retrieve the connection string value
   -->
      <!-- from the web.config file.                            -->
      <asp:sqldatasource id="DetailsViewSource"
        selectcommand="Select [CustomerID], [CompanyName], [Address], 
          [City], [PostalCode], [Country] From [Customers]"
        updatecommand="Update [Customers] Set 
          [CompanyName]=@CompanyName, [Address]=@Address, 
          [City]=@City, [PostalCode]=@PostalCode, 
          [Country]=@Country 
          Where [CustomerID]=@CustomerID"
        connectionstring=
          "<%$ ConnectionStrings:NorthWindConnectionString%>" 
        runat="server"/>
          
    </form>
  </body>
</html>

プラットフォーム

Windows 98, Windows 2000 SP4, 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

参照

関連項目
System.Web.UI.WebControls 名前空間
DetailsView クラス
DetailsViewUpdateEventArgs クラス
DetailsView.ItemUpdating イベント
OnItemUpdated
その他の技術情報
イベントとデリゲート

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DetailsViewUpdateEventHandler デリゲートとは？ わかりやすく解説

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DetailsViewUpdateEventHandler デリゲートとは？わかりやすく解説