Disable ASP.Net GridView cell in Edit mode based on condition using C# and VB.Net

How to disable only column cell that contain value

The user can only edit empty column in gridview in asp.net web form

protected void GridView4_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        for (int i = 0; i < e.Row.Cells.Count; i++)
        {
            if (e.Row.Cells[i].Text == "&nbsp;")
            {

            }
            else
            {
                e.Row.Cells[i].Enabled = false;
            }
        }
    }
}