DataControlField.ExtractValuesFromCell 方法

public:
 virtual void ExtractValuesFromCell(System::Collections::Specialized::IOrderedDictionary ^ dictionary, System::Web::UI::WebControls::DataControlFieldCell ^ cell, System::Web::UI::WebControls::DataControlRowState rowState, bool includeReadOnly);

public virtual void ExtractValuesFromCell (System.Collections.Specialized.IOrderedDictionary dictionary, System.Web.UI.WebControls.DataControlFieldCell cell, System.Web.UI.WebControls.DataControlRowState rowState, bool includeReadOnly);

abstract member ExtractValuesFromCell : System.Collections.Specialized.IOrderedDictionary * System.Web.UI.WebControls.DataControlFieldCell * System.Web.UI.WebControls.DataControlRowState * bool -> unit
override this.ExtractValuesFromCell : System.Collections.Specialized.IOrderedDictionary * System.Web.UI.WebControls.DataControlFieldCell * System.Web.UI.WebControls.DataControlRowState * bool -> unit

Public Overridable Sub ExtractValuesFromCell (dictionary As IOrderedDictionary, cell As DataControlFieldCell, rowState As DataControlRowState, includeReadOnly As Boolean)

參數

範例

下列程式碼範例示範如何為衍生自 類別的 DataControlField 控制項實 ExtractValuesFromCell 作 方法。 類別 RadioButtonField 會呈現 控制項中 GridView 每個資料列的資料繫結選項按鈕。 ExtractValuesFromCell呼叫 方法時，方法會嘗試判斷儲存格中包含的物件目前值 RadioButton 是否已選取或清除，並將值新增至 IDictionary 集合。 此程式碼範例是針對 類別提供的較大範例的 DataControlField 一部分。

// This method is called by the ExtractRowValues methods of 
// GridView and DetailsView. Retrieve the current value of the 
// cell from the Checked state of the Radio button.
public override void ExtractValuesFromCell(IOrderedDictionary dictionary,
                                           DataControlFieldCell cell,
                                           DataControlRowState rowState,
                                           bool includeReadOnly)
{

  // Determine whether the cell contains a RadioButton 
  // in its Controls collection.
  if (cell.Controls.Count > 0) {
    RadioButton radio = cell.Controls[0] as RadioButton;

    object checkedValue = null;
    if (null == radio) {
      // A RadioButton is expected, but a null is encountered.
      // Add error handling.
      throw new InvalidOperationException
          ("RadioButtonField could not extract control.");
    }
    else {
        checkedValue = radio.Checked;
    }

    // Add the value of the Checked attribute of the
    // RadioButton to the dictionary.
    if (dictionary.Contains(DataField))
      dictionary[DataField] = checkedValue;
    else
      dictionary.Add(DataField, checkedValue);
  }
}

' This method is called by the ExtractRowValues methods of
' GridView and DetailsView. Retrieve the current value of the 
' cell from the Checked state of the Radio button.
Public Overrides Sub ExtractValuesFromCell( _
    ByVal dictionary As IOrderedDictionary, _
    ByVal cell As DataControlFieldCell, _
    ByVal rowState As DataControlRowState, _
    ByVal includeReadOnly As Boolean)
    ' Determine whether the cell contain a RadioButton 
    ' in its Controls collection.
    If cell.Controls.Count > 0 Then
        Dim radio As RadioButton = CType(cell.Controls(0), RadioButton)

        Dim checkedValue As Object = Nothing
        If radio Is Nothing Then
            ' A RadioButton is expected, but a null is encountered.
            ' Add error handling.
            Throw New InvalidOperationException( _
                "RadioButtonField could not extract control.")
        Else
            checkedValue = radio.Checked
        End If


        ' Add the value of the Checked attribute of the
        ' RadioButton to the dictionary.
        If dictionary.Contains(DataField) Then
            dictionary(DataField) = checkedValue
        Else
            dictionary.Add(DataField, checkedValue)
        End If
    End If
End Sub

備註

方法 ExtractValuesFromCell 是由衍生自 DataControlField 的類型所實作，以在適用的情況下將目前欄位與值產生關聯。 欄位/值組會儲存在 dictionary 傳遞至 方法的集合中。 方法 ExtractValuesFromCell 是由 ExtractRowValues 和 等 DetailsViewGridView 資料控制項的 方法呼叫。

當您撰寫使用 DataControlFieldCell 物件來組合一組儲存格及其相關聯值的自訂資料繫結控制項時，請呼叫這個方法。 當您撰寫衍生自 DataControlField 的類別，以顯示使用者資料或資料系結資料時，請實作這個方法。 並非所有衍生類型都實作 ExtractValuesFromCell 方法，因為並非所有欄位都會顯示使用者資料。 例如， ButtonField 控制項會顯示按鈕，而且沒有使用者資料。

適用於

另請參閱

• InitializeCell(DataControlFieldCell, DataControlCellType, DataControlRowState, Int32)