UserControl.SaveViewState メソッドとは何？わかりやすく解説 Weblio辞書

.NET Framework クラスライブラリリファレンス

索引トップ用語の索引ランキング

UserControl.SaveViewState メソッド

最後のページのポストバック以後に発生した、ユーザーコントロールのビューステートの変更を保存します。

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

Visual Basic (宣言)

Protected Overrides Function
 SaveViewState As Object

Visual Basic (使用法)

Dim returnValue As Object

returnValue = Me.SaveViewState

protected override Object SaveViewState ()

C++

protected:
virtual Object^ SaveViewState () override

protected Object SaveViewState ()

JScript

protected override function SaveViewState ()
 : Object

戻り値
ユーザーコントロールの現在のビューステートを返します。コントロールに関連付けられているビューステートがない場合は、null 参照 (Visual Basic では Nothing) を返します。

解説

通常、このメソッドを呼び出す必要はありません。ただし、ビューステートにカスタム情報を格納している場合は、このメソッドをオーバーライドして情報を復元します。

使用例

LoadViewState メソッドと SaveViewState メソッドを使用してビューステートを管理するユーザーコントロールの例を次に示します。

Visual Basic

   
    Public Property UserText() As
 String

        Get
            Return CStr(ViewState("usertext"))
        End Get
        Set(ByVal value As
 String)
            ViewState("usertext") = value
        End Set

    End Property
   
    Public Property PasswordText() As
 String

        Get
            Return CStr(ViewState("passwordtext"))
        End Get
        Set(ByVal value As
 String)
            ViewState("passwordtext") = value
        End Set

    End Property
   
    <System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand,
 Name:="FullTrust")> _
    Protected Overrides Sub
 LoadViewState(ByVal savedState As Object)

        Dim totalState As Object()
 = Nothing
        If Not (savedState Is
 Nothing) Then
            totalState = CType(savedState, Object())
            If totalState.Length <> 3 Then
                ' Throw an appropriate exception.
            End If
            ' Load base state.
            MyBase.LoadViewState(totalState(0))
            ' Load extra information specific to this control.
            If Not (totalState Is
 Nothing) AndAlso Not (totalState(1)
 Is Nothing) AndAlso Not (totalState(2) Is Nothing) Then
                UserText = CStr(totalState(1))
                PasswordText = CStr(totalState(2))
            End If
        End If

    End Sub
     
    <System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand,
 Name:="FullTrust")> _
    Protected Overrides Function
 SaveViewState() As Object

        Dim baseState As Object
 = MyBase.SaveViewState()
        Dim totalState(2) As Object
        totalState(0) = baseState
        totalState(1) = user.Text
        totalState(2) = password.Text
        Return totalState

    End Function
End Class

public string UserText
{
    get
    {
        return (string)ViewState["usertext"];
    }
    set
    {
        ViewState["usertext"] = value;
    }
}
public string PasswordText
{
    get
    {
        return (string)ViewState["passwordtext"];
    }
    set
    {
        ViewState["passwordtext"] = value;
    }
}

[System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand,
 Name="FullTrust")] 
protected override void LoadViewState(object
 savedState) 
{
    object[] totalState = null;       
    if (savedState != null)
    {
        totalState = (object[])savedState;
        if (totalState.Length != 3)
        {
            // Throw an appropriate exception.
        }
        // Load base state.
        base.LoadViewState(totalState[0]);
        // Load extra information specific to this control.
        if (totalState != null && totalState[1]
 != null && totalState[2] != null)
        {
            UserText = (string)totalState[1];
            PasswordText = (string)totalState[2];
        }
    }

}

[System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand,
 Name="FullTrust")] 
protected override object SaveViewState()
{
    object baseState = base.SaveViewState();
    object[] totalState = new object[3];
    totalState[0] = baseState;
    totalState[1] = user.Text;
    totalState[2] = password.Text;
    return totalState;
}