Question

I am trying to add a parameter to the deleting event of an ObjectDataSource as in the example below from msdn. I generated an event handler for the ObjectDataSource’s deleting event, and it had the same signature as in the example, however, when I try to clear the paramsFromPage as in the example, I receive an error stating that paramsFromPage is readonly. Is there something I need to change somewhere else?

This example comes from the following msdn page:

http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.objectdatasource.deleting%28v=VS.90%29.aspx

Private Sub NorthwindEmployeeDeleting(ByVal source As Object, ByVal e As ObjectDataSourceMethodEventArgs)

    ' The GridView passes the ID of the employee
    ' to be deleted. However, the business object, EmployeeLogic,
    ' requires a NorthwindEmployee parameter, named "ne". Create
    ' it now and add it to the parameters collection.
    Dim paramsFromPage As IDictionary = e.InputParameters

    If Not paramsFromPage("EmpID") Is Nothing Then

        Dim ne As New NorthwindEmployee(paramsFromPage("EmpID").ToString())
        ' Remove the old EmpID parameter.
        paramsFromPage.Clear()
        paramsFromPage.Add("ne", ne)


    End If
End Sub ' NorthwindEmployeeDeleting

EDIT:
The following is my code

Protected Sub QueueDataSource_Deleting(ByVal sender As Object, ByVal e As ObjectDataSourceMethodEventArgs) Handles QueueDataSource.Deleting
    Dim paramsFromPage As IDictionary = e.InputParameters
    Dim queue As New QueueData

    If Not paramsFromPage("QueueNamek__BackingField") Is Nothing Then
        queue.QueueNamek__BackingField = paramsFromPage("QueueNamek__BackingField")
    End If

    If Not paramsFromPage("ServerNamek__BackingField") Is Nothing Then
        queue.ServerNamek__BackingField = paramsFromPage("ServerNamek__BackingField")
    End If

    paramsFromPage.Add("queue", queue)
End Sub

The error “The OrderedDictionary is readonly and cannot be modified.” is thrown when an attempt is made to Add to the ordered dictionary.

Answer 1

I found a good workaround to the solution Microsoft suggested. I discovered that while parameters cannot be added or removed programmatically, they can be added declaratively, and the parameters needed for the delete function are added automatically. Also, the parameters that are in the collection can be modified programatically inside the deleting event.

Here is my solution:

' Store the index of the row being deleted
Protected Sub QueueGrid_RowDeleting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewDeleteEventArgs) Handles QueueGrid.RowDeleting
    rowChosen = e.RowIndex
End Sub

' Prepare parameter to be sent to deleting function
Protected Sub QueueDataSource_Deleting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.ObjectDataSourceMethodEventArgs) Handles QueueDataSource.Deleting
    Dim queue As QueueData = e.InputParameters("queue")

    With queue
        .QueueNamek__BackingField = QueueGrid.Rows(rowChosen).Cells(2).Text
        .ServerNamek__BackingField = QueueGrid.Rows(rowChosen).Cells(3).Text
    End With
End Sub

I am just wondering if there is a better way to get the data from the cells so that changing the column order does not break this code.