ImageField X contiene un control que no es un TextBox en modo de edición ni Image o Label en modo de sólo lectura. Reemplace OnDataBindField para que herede de ImageField y agregue controles distintos.
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English version
ImageField X contains a control that isn't a TextBox in edit mode, or an Image and a Label in read-only mode. Override OnDataBindField to inherit from ImageField and add different controls.
.Net Framework