protected override void OnTextBoxTextChanged(EventArgs e)
    {
        GridEXFilterCondition internalFilter = new GridEXFilterCondition();

        String str = TextBox.Text;

        foreach (GridEXColumn column in DropDownList.Columns)
        {
            if (!column.Visible)
            {
                continue;
            }

            GridEXFilterCondition filterCondition = new GridEXFilterCondition(column, ConditionOperator.Contains, str);

            internalFilter.AddCondition(LogicalOperator.Or, filterCondition);
        }

        DropDownList.ApplyFilter(internalFilter);
    }