I have a user control in VB.Net which creates a dynamic RadDropDownList at runtime. The create code is as follows
Private Sub SetControl()
Try
Dim list As New RadDropDownList
list.Font = mFont
list.Location = New Point(213, 0)
list.Size = New Size(225, 25)
LoadList(list)
list.Name = "userCTRL"
Me.Controls.Add(list)
Catch ex As Exception
Dim x As String = ex.Message
End Try
End Sub
Private Sub LoadList(ByRef lst As RadDropDownList)
Dim strSQL As String = "SELECT AssetTypeAttributeListValueId, Label FROM dbo.AssetTypeAttributeListValue WHERE AssetTypeAttributeId = " & AttributeTypeId & " ORDER BY SortOrder"
Dim ds As DataSet = CLIB_MAPPS.Configuration.DBAccess.getDataSet(strSQL, "Attribute")
If ds.Tables(0).Rows.Count > 0 Then
lst.ValueMember = "AssetTypeAttributeListValueId"
lst.DisplayMember = "Label"
lst.DataSource = ds.Tables(0)
End If
End Sub
Another Public property of the user control sets the value of the control from the form that contains this user control. Here is the public property of the user control:
Public Property CollectedValue() As String
Get
GetValue()
Return mCollectedValue
End Get
Set(ByVal value As String)
mCollectedValue = value
SetValue()
End Set
End Property
When the value is set it calls the SetValue() routine to find the RadDropDownList control and set its value
Private Sub SetValue()
Try
Dim list As RadDropDownList = CType(Me.Controls("userCTRL"), RadDropDownList)
If mCollectedValue = "" Then
list.SelectedIndex = -1
Else
list.SelectedValue = CInt(mCollectedValue)
End If
Catch ex As Exception
Dim x As String = ex.Message
End Try
End Sub
After I create a local instance of the RadDropDownList called "list", I attempt to set the SelectedValue, and it will not change. It is acting almost like the control doesn't exist, but doesn't throw any errors. In the Debug mode, I can see that SelectedIndex is -1 and SelectedValue is Nothing, and is of type "Object". If I view the value of list in the Quick Watch, it clearly shows it set as a control of type RadDropDownList, and it contains the list items I added when the control was created. Also, if I stop it in Debug on the IF statement in SetValue() and expand the variable called "list" to see all its properties, then immediately close the Debug window, it recognizes the SelectedIndex and SelectedValue and it sets them properly. Once I do that, the SelectedValue type also immediately changes to "Object(Integer)".
I'm not sure how to adequately explain this, but everything I have tried to get it to recognize the properties of "list" does not seem to work. Clearly stopping the code, opening in the Quick Watch in Debug and expanding the "list" variable to see the properties does something to allow the "list" variable to be fully loaded and its properties available. I tried Application.DoEvents(), and other events after creating "list", but nothing seems to work.
Thoughts?
2 Answers, 1 is accepted
Following the provided sample code snippet, I have prepared a sample project to test the behavior. I was able to observe the described problem when setting the SelectedValue property of RadDropDownList.
I have noticed that you set the DataSource property before adding the RadDropDownList in the Controls collection and before initializing its BindingContext. That is why in order to get the desired value selected when you set the UserControl11.CollectedValue property, it is necessary to initialize the RadDropDownList.BindingContext property before setting its DataSource.
I have attached my sample project for your reference.
I hope this information helps. If you need any further assistance please don't hesitate to contact me.
Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik
Rank 1
Dess,
This worked perfectly.
I'm glad you understood my ramblings and was able to recreate my issue. I knew I was missing something in creating this control dynamically, but couldn't figure it out.
Thanks again for your quick response and assistance!