How to use Regular Expression to highlight characters inside GridView using C# in ASP.Net

Hi EmadKhan,

Refer the below code.

HTML

<div>
    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" AllowPaging="true"
        Caption="ORIGINAL STATE">
        <Columns>
            <asp:BoundField DataField="Text1" HeaderText="Text1" />
            <asp:BoundField DataField="Text2" HeaderText="Text2" />
            <asp:BoundField DataField="Text3" HeaderText="Text3" />
            <asp:BoundField DataField="Text4" HeaderText="Text4" />
            <asp:BoundField DataField="Text5" HeaderText="Text5" />
        </Columns>
    </asp:GridView>
    <br />
    <asp:GridView ID="GridView2" runat="server" AutoGenerateColumns="false" AllowPaging="true"
        OnRowDataBound="OnRowDataBound" Caption="WANTED STATE">
        <Columns>
            <asp:BoundField DataField="Text1" HeaderText="Text1" />
            <asp:BoundField DataField="Text2" HeaderText="Text2" />
            <asp:BoundField DataField="Text3" HeaderText="Text3" />
            <asp:BoundField DataField="Text4" HeaderText="Text4" />
            <asp:BoundField DataField="Text5" HeaderText="Text5" />
        </Columns>
    </asp:GridView>
</div>

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[5] { new DataColumn("Text1"), new DataColumn("Text2"), new DataColumn("Text3"), new DataColumn("Text4"), new DataColumn("Text5") });
        dt.Rows.Add("1", "Builder", "1234", "something,good", "Invalid");
        dt.Rows.Add("2", "!)@(#*", "good", "good", "good");
        dt.Rows.Add("3", "&-,.", "perfect", "`~!@#$%^*()_+={[}];:'\",<>/?\\|", "perfect,poor");
        GridView1.DataSource = dt;
        GridView1.DataBind();
        GridView2.DataSource = dt;
        GridView2.DataBind();
    }
}

protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        var searches = new[] { "]", "`", "~", "!", "@", "#", "$,", "%", "^", "*", "(", ")", "_", "+", "=", "{", "}", ";", ":", "'", "\"", ",", "<", ">", "/", "?", @"\\", "|", "[" };
        var regex = "[" + String.Join("", searches) + "]";
        for (int i = 0; i < e.Row.Cells.Count; i++)
        {
            e.Row.Cells[i].Text = Regex.Replace(System.Net.WebUtility.HtmlDecode(e.Row.Cells[i].Text), regex, delegate(Match match)
            {
                return string.Format("<span style = 'color:Red'>{0}</span>", match.Value);
            }, RegexOptions.IgnoreCase);
        }
    }
}

Output