How to validate only characters in Textbox ASP.NET C# (textbox only takes given characters not other characters) - textbox valid characters - ajax control toolkit

  <asp:TextBox ID="txtLevel" Width="80%" CssClass="form-control" runat="server" 

                    MaxLength="6"></asp:TextBox>

                <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="txtLevel" SetFocusOnError="true" Display="None" ErrorMessage="Enter Level Name"></asp:RequiredFieldValidator>

                <cc1:ValidatorCalloutExtender ID="reqVal" runat="server" TargetControlID="RequiredFieldValidator1"></cc1:ValidatorCalloutExtender>

                 <cc1:FilteredTextBoxExtender ID="levelFilter" TargetControlID="txtLevel" runat="server" FilterMode="ValidChars" ValidChars="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-/"></cc1:FilteredTextBoxExtender>

Textbox with Uppercase and remove some characters in C# ASP.NET

 <asp:TextBox ID="txt_regid" runat="server" Style="text-transform: uppercase;" Width="250px"

                        CssClass="form-control" placeholder="Enter Student Reg. ID">

                    </asp:TextBox>

                    <cc1:FilteredTextBoxExtender ID="filterRegid" TargetControlID="txt_regid" FilterMode="InvalidChars"

                        InvalidChars="!@#$%^&*()+=<>{}[]|\?/.,';:" runat="server">

                    </cc1:FilteredTextBoxExtender>

Textbox with calendar in ASP.NET C#

 <td>  Date of Birth <span style="color:Red;">*</span></td>

            <td>

                <asp:TextBox ID="txt_dob" runat="server" CssClass="form-control"  required="" x-moz-errormessage="Enter Date of Birth"

                    placeholder="Date of Birth"></asp:TextBox>

                <cc1:CalendarExtender ID="txt_calender" runat="server" Format="dd/MM/yyyy" TargetControlID="txt_dob">

                </cc1:CalendarExtender>

                <asp:CompareValidator ID="cfvDOB" ForeColor="Red" ControlToValidate="txt_dob" Type="Date" Operator="LessThan"

                            ErrorMessage="(Age can't be less than 15 years)" Display="Dynamic"  ValidationGroup="Save2"

                            runat="server"></asp:CompareValidator>

                            <asp:RequiredFieldValidator ID="reqval" runat="server" ValidationGroup="Save2" ErrorMessage="Enter Date of Birth" ForeColor="Red" ControlToValidate="txt_dob">

                            </asp:RequiredFieldValidator>

            </td>

ASP.NET C# masking without gif image progress (please wait or processing)

 <fieldset style="width:100%;">

               <legend >Student Details Report </legend>

            <div>

            <center>

             <asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="UpdpnlStudents" >

             <ProgressTemplate>

            <b style="color:Green"> Processing...</b>

             </ProgressTemplate>

             </asp:UpdateProgress>

             </center>

             </div>

            <asp:UpdatePanel ID="UpdpnlStudents" runat="server" UpdateMode="Conditional">

            <ContentTemplate>

</ContentTemplate>

<asp:PostBackTrigger ControlID="imgexcel" />

            <asp:PostBackTrigger ControlID="imgepdf" />

            </Triggers>

           

             </asp:UpdatePanel>

 </fieldset>  

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Also we can use AjaxControlToolkit :-

We can download from below link:-

https://www.nuget.org/packages/AjaxControlToolkit/

https://drive.google.com/file/d/1Dq-390V6NBVmTyavKmqY5DBhskgVwsdj/view?usp=sharing