adding and removing dynamic column on Gridview

Question

Hi There,

I am having an asp GridView with 3 bound columns.
I am adding dynamic column to that  gridview (number of columns depends on the selected value from the dropdown) on page_init.
also those dynamic column contains textbox as a control inside.
First time column added successfully(say suppose 4 columns), but if user reduces the number of column (say 2 columns are added now), then two column added successfully but 2 out of 4 column that are added before remains on the grid with no textbox control.

I also change the column Header text on the RowCreated event .

how to remove columns that are previously added?

Thanks in advance :