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lately I have been trying to develop a custom field (cascading dropdown) for sharepoint 2010. I am using the sample from codeplex. the problem is that the sample is for sharepoint 2007 and uses the as follows in XML.

 <PropertySchema>
  <Fields>
    <Field Name="SiteUrl" Hidden="TRUE" DisplayName="SiteUrl" MaxLength="500" DisplaySize="100" Type="Text">
    </Field>

for some reason in Sharepoint 2010 this seems not to be working and is giving the following error:

System.InvalidCastException: Unable to cast object of type 'ASP._controltemplates_cascadingdropdowneditfieldcontrol_ascx' to type 'Microsoft.SharePoint.WebControls.IFieldEditor'.
at Microsoft.SharePoint.ApplicationPages.FieldCustomizationPage.CreateChildControls()
at Microsoft.SharePoint.ApplicationPages.FieldNewPage.CreateChildControls()
at System.Web.UI.Control.EnsureChildControls()
at Microsoft.SharePoint.ApplicationPages.FieldCustomizationPage.OnLoad(EventArgs e)
at Microsoft.SharePoint.ApplicationPages.FieldNewPage.OnLoad(EventArgs e)
at System.Web.UI.Control.LoadRecursive()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

is there a way to add same things in CreateChildControl instead of PropertySchema?? or anyone has suggestions to solve this issue?

  • Could you link to the example on CodePlex, please? – Stu Pegg Aug 30 '11 at 12:12
  • hi, the following is the link to what seems like the project, I managed to find same one open source but did not keep the link :S. basically it is the same as this one cascddlistwithfilter.codeplex.com – IanCian Aug 30 '11 at 12:46
  • I can post the xml file if it is of any help, and the class using ifieldeditor main parts – IanCian Aug 30 '11 at 12:47
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Found this site which did the cascading drop down very easily: please refer to http://www.sharepointkings.com/2010/09/sharepoint-cascading-drop-downs-using.html

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This error may occure if your custom editor control 'ASP._controltemplates_cascadingdropdowneditfieldcontrol_ascx does not implement IFieldEditor interface or doing it wrong. MSDN recommends to use custom editor controls. Here is another greate example to start with. Hope it helps!

  • Bassist's answer is the correct one BTW. The lack of implementing the IFieldEditor interface is what would cause this error. The "Answer" to DL a new sample doesn't address the actual error and is not the solution to the problem. – Manic Farmer Aug 20 '18 at 21:58

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