How to filter datagridview with if condition

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C#

WinForms

Hi I am filtering my datagridview using a combobox. I wanna get a message telling me that the choosen value can't be found because the column name doesn't exit in the datagridview.
where I'm stock is the second else if statement.

private void cbFilterEU_SelectedIndexChanged(object sender, EventArgs e)
        {
            
            string check = cbFilterEU.SelectedItem.ToString();
            if (check == "All")
            {
                MessageBox.Show("All Data !!!");

            }

            else if (cbFillFilterEIU.SelectedItem != null)
            {
                //Check an see what's in the dgv
                DataView dv = new DataView(dt);
                // now filter
                dv.RowFilter = " [Areacode] = " + cbFilterEU.Text.Trim();
                MessageBox.Show("AREACODE");
                datagridview1.DataSource = dv;
            }
		else if
{
/* Wanna look through the datagridview for the column name and if not present show message
                MessageBox.Show("Can't find the column");
             */
}

I tried something like this but no success

//else if (cbFilterEU.SelectedItem != null && datagridview1 == null)
           //{
           //    MessageBox.Show("Can't find the column");
           //}