Regular Expression Regex to accept only Alphanumeric Alphabets and Numbers in TextBox in ASPNet

In this article I will explain with an example, how to use Regular Expression (Regex) to accept/allow only Alphanumeric characters i.e. Alphabets (Upper and Lower case) and Numbers (Digits) in TextBox in ASP.Net using:-

1. RegularExpression Validator.

2. JavaScript.

3. jQuery.

1. Regular Expression (Regex) to accept only Alphanumeric (Alphabets and Numbers) 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) 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]*$" ErrorMessage="*Valid characters: Alphabets and Numbers." />

<br />

<asp:Button ID="Button1" Text="Validate" runat="server" />

2. Regular Expression (Regex) to accept only Alphanumeric (Alphabets and Numbers) 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 or Numbers then an error message is displayed.

<asp:TextBox ID="TextBox2" runat="server" />

<br />

<span id="spnError" style="color: Red; display: none">*Valid characters: Alphabets and

Numbers.</span>

<br />

<asp:Button ID="Button2" Text="Validate" runat="server" CausesValidation="false"

OnClientClick="return Validate()" />

function Validate() {

var isValid = false;

var regex = /^[a-zA-Z0-9]*$/;

isValid = regex.test(document.getElementById("<%=TextBox2.ClientID %>").value);

document.getElementById("spnError").style.display = !isValid ? "block" : "none";

return isValid;

}

</script>

3. Regular Expression (Regex) to accept only Alphanumeric (Alphabets and Numbers) 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 or Numbers then an error message is displayed.

<asp:TextBox ID="TextBox3" runat="server" />

<br />

<span id="spnError2" style="color: Red; display: none">*Valid characters: Alphabets

and Numbers.</span>

<br />

<asp:Button ID="btnValidate" Text="Validate" runat="server" CausesValidation="false" />