Bind DropDownList in ItemTemplate of ASP.Net GridView Control

Use RowDataBoundEvent to Bind

protected void RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            DropDownList ddlCities = (DropDownList)e.Row.FindControl("ddlCities");
            string query = "select distinct city from customers";
            SqlCommand cmd = new SqlCommand(query);
            ddlCities.DataSource = GetData(cmd);
            ddlCities.DataTextField = "city";
            ddlCities.DataValueField = "city";
            ddlCities.DataBind();
        }
    }