In this article I will explain with an example, how to use Regular Expression (Regex) to accept/allow Alphanumeric characters i.e. Alphabets (Upper and Lower case) and Numbers (Digits) and Space in TextBox in ASP.Net using:-
1. RegularExpression Validator.
2. JavaScript.
3. jQuery.
 
 
1. Regular Expression to accept Alphanumeric (Alphabets and Numbers) and Space in TextBox using RegularExpression Validator
The following HTML Markup consists of a TextBox, a Button and a RegularExpression Validator which has been applied with the Regular Expression (Regex) to accept only Alphanumeric characters i.e. Alphabets (Upper and Lower case) and Numbers (Digits) and Space as valid characters.
<asp:TextBox ID="TextBox1" runat="server" />
<br />
<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ControlToValidate="TextBox1"
    ForeColor="Red" ValidationExpression="[a-zA-Z0-9\s]*$" ErrorMessage="Valid characters: Alphabets, Numbers and Space." />
<br />
<asp:Button ID="Button1" Text="Validate" runat="server" />
 
 
2. Regular Expression to accept Alphanumeric (Alphabets and Numbers) and Space in TextBox using JavaScript
The following HTML Markup consists of a TextBox, a Button and an HTML SPAN. On the OnClientClick event of the Button, a JavaScript function is executed which validates the TextBox text against the Regular Expression (Regex) and if it contains character other than Alphabets, Numbers or Space then an error message is displayed.
<asp:TextBox ID="TextBox2" runat="server" />
<br />
<span id="spnError" style="color: Red; display: none">Valid characters: Alphabets, Numbers
    and Space.</span>
<br />
<asp:Button ID="Button2" Text="Validate" runat="server" CausesValidation="false"
    OnClientClick="return Validate()" />
<script type="text/javascript">
    function Validate() {
        var isValid = false;
        var regex = /^[a-zA-Z0-9\s]*$/;
        isValid = regex.test(document.getElementById("<%=TextBox2.ClientID %>").value);
        document.getElementById("spnError").style.display = !isValid ? "block" : "none";
        return isValid;
    }
</script>
 
 

3. Regular Expression to accept Alphanumeric (Alphabets and Numbers) and Space in TextBox using jQuery
The following HTML Markup consists of a TextBox, a Button and an HTML SPAN. To the Button a jQuery click event handler is attached thus when the button is clicked, the TextBox text is validated against the Regular Expression (Regex) and if it contains character other than Alphabets, Numbers or Space then an error message is displayed.
<asp:TextBox ID="TextBox3" runat="server" />
<br />
<span id="spnError2" style="color: Red; display: none">*Valid characters: Alphabets,
    Numbers and Space.</span>
<br />
<asp:Button ID="btnValidate" Text="Validate" runat="server" CausesValidation="false" />
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
    $(function () {
        $("[id*=btnValidate]").bind("click", function () {
            var isValid = false;
            var regex = /^[a-zA-Z0-9\s]*$/;
            isValid = regex.test($("[id*=TextBox3]").val());
            $("#spnError2").css("display", !isValid ? "block" : "none");
            return isValid;
        });
    });
</script>
 
 
Screenshot
Regular Expression to accept Alphanumeric (Alphabets and Numbers) and Space in TextBox in ASP.Net
 
 
Demo
 
 
Browser Compatibility

The above code has been tested in the following browsers.

Internet Explorer  FireFox  Chrome  Safari  Opera 

* All browser logos displayed above are property of their respective owners.

 
 
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