Question

I am trying to pass a collection of Dropdown controls as a parameter to a method which takes a collection of type Control as input. While executing I get the following error:

“Unable to cast object of type ‘d__a31[System.Web.UI.WebControls.DropDownList]' to type 'System.Collections.Generic.IEnumerable1[System.Web.UI.Control]’.”

Any idea why am I getting this?

My code:

private void Caller()
{
   IEnumerable<DropDownList> dropDownControlsInCurrentRow = currentRow.Controls.OfType<DropDownList>();
   SetControlsVisibility(dropDownControlsInCurrentRow, false);
}

private void SetControlsVisibility(IEnumerable<Control> controlCollection, bool visibilityFlag)
{
   foreach (ctrl in controlCollection) {
         ctrl.Visible = visibilityFlag;
   }
}

Answer 1

use

IEnumerable<Control> dropDownControlsInCurrentRow;

instead of

IEnumerable<DropDownList> dropDownControlsInCurrentRow;