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ExtractValuesFromCell Method

DataControlField.ExtractValuesFromCell Method

Extracts the value of the data control field from the current table cell and adds the value to the specified IDictionary collection.

Namespace:  System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)

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


Type: System.Collections.Specialized.IOrderedDictionary

An IOrderedDictionary.

Type: System.Web.UI.WebControls.DataControlFieldCell

A DataControlFieldCell that contains the text or controls of the DataControlField.

Type: System.Web.UI.WebControls.DataControlRowState

One of the DataControlRowState values.

Type: System.Boolean

true to indicate that the values of read-only fields are included in the dictionary collection; otherwise, false.

The ExtractValuesFromCell method is implemented by types derived from DataControlField to associate the current field with a value, if applicable. The field/value pair is stored in the dictionary collection that is passed to the method. The ExtractValuesFromCell method is called by the ExtractRowValues method of data controls such as DetailsView and GridView.

Call this method when you are writing a custom data-bound control that uses DataControlFieldCell objects to assemble a set of cells and their associated values. Implement this method when you are writing a class derived from DataControlField that displays user data or data-bound data. Not all derived types implement the ExtractValuesFromCell method, because not all fields display user data. For example, the ButtonField control displays a button and has no user data.

The following code example demonstrates how to implement the ExtractValuesFromCell method for a control that derives from the DataControlField class. The RadioButtonField class renders a data-bound radio button for every row in a GridView control. When the ExtractValuesFromCell method is called, the method attempts to determine whether the current value of the RadioButton object contained in the cell is selected or cleared, and adds the value to the IDictionary collection. This code example is part of a larger example provided for the DataControlField class.

' 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.")
            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
            dictionary.Add(DataField, checkedValue)
        End If 
    End If 
End Sub

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0
© 2015 Microsoft