Custom Filter

Hi guys,

So I was following this telerik video on the 3 types of filtering (basic, excel-like, custom) :  https://www.telerik.com/videos/winforms/filtering-and-expressions-in-radgridview-for-winforms

I tried to apply the custom filtering using a textbox just like the video on my project, but I keep getting an error.  It's suppose to search all the rows and match what's in the textbox.  It'll run, but as soon as I try typing into the textbox, I get an error.  What am I doing incorrectly?

I've attached some pics of it and the code as well.  Thank you!

Here is my code:

 private void ProductionInstructionPrintPage_Load(object sender, EventArgs e)
        {
            // TODO: This line of code loads data into the 'dbMTISysDataSet.VW_ProdPrintPage' table. You can move, or remove it, as needed.
            this.vW_ProdPrintPageTableAdapter.Fill(this.dbMTISysDataSet.VW_ProdPrintPage);

            this.WindowState = FormWindowState.Maximized;

            radGridView1.EnableFiltering = true;
            radGridView1.EnableCustomFiltering = true;

        }

private void radTextBox1_TextChanged(object sender, EventArgs e)
        { 

            radGridView1.MasterTemplate.Refresh();
        }

        private void radGridView1_CustomFiltering(object sender, GridViewCustomFilteringEventArgs e)
        {
            // if the custom filter is empty, reset this row to its default state
            if (string.IsNullOrEmpty(radTextBox1.Text))
            {
                e.Visible = true;

                //reset each cell in this row
                for (int i=0; i<radGridView1.ColumnCount; i++)
                {
                    e.Row.Cells[i].Style.Reset();
                    e.Row.InvalidateRow();
                }

                return;
            }

            //if the custom filter is set, locate the cells in this row that match it and colorize them
            e.Visible = false;
            for (int i = 0; i<radGridView1.ColumnCount; i++)
            {
                string text = e.Row.Cells[i].Value.ToString();

                //locate and colorize matching cells
                if (text.IndexOf(radTextBox1.Text, StringComparison.InvariantCultureIgnoreCase) >= 0)
                {
                    e.Row.Cells[i].Style.CustomizeFill = true;
                    e.Row.Cells[i].Style.DrawFill = true;
                    e.Row.Cells[i].Style.BackColor = Color.PowderBlue;
                    e.Visible = true;
                }
                else
                {
                    e.Row.Cells[i].Style.Reset();
                    e.Row.InvalidateRow();
                }
            }
        }