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
Windows Forms (WinForms) Application using C# and VB.Net.
Form Design
The following Form consists of:
TextBox – For capturing Alphanumeric characters.
Label – For showing error message.
Button – For validating Alphanumeric characters.
![Regular Expression (Regex) to accept only Alphanumeric (Alphabets and Numbers) in C# and VB.Net]()
The Button has been assigned with the Click event handler.
![Regular Expression (Regex) to accept only Alphanumeric (Alphabets and Numbers) in C# and VB.Net]()
Namespaces
You will need to import the following namespace.
C#
using System.Text.RegularExpressions;
VB.Net
Imports System.Text.RegularExpressions
Regular Expression (Regex) to accept only Alphanumeric (Alphabets and Numbers)
Regular Expression (Regex)
Explanation
Alphabets (Upper and Lower case) and Numbers (Digits) as valid characters.
Example
When the
Validate Button is clicked, the value of the
TextBox is validated against the
Regular Expression (Regex) and if invalid, the error message is displayed.
C#
private void OnValidate(object sender, EventArgs e)
{
lblError.Hide();
Regex regex = new Regex(@"^[a-zA-Z0-9]*$");
if (!string.IsNullOrEmpty(txtAlphaNumeric.Text.Trim()))
{
if (!regex.IsMatch(txtAlphaNumeric.Text.Trim()))
{
lblError.Show();
}
}
else
{
lblError.Text = "Alphanumeric characters are required";
lblError.Show();
}
}
VB.Net
Private Sub OnValidate(sender As Object, e As EventArgs) Handles btnValidate.Click
lblError.Hide()
Dim regex As Regex = New Regex("^[a-zA-Z0-9]*$")
If Not String.IsNullOrEmpty(txtAlphaNumeric.Text.Trim())Then
If Not regex.IsMatch(txtAlphaNumeric.Text.Trim())Then
lblError.Show()
End If
Else
lblError.Text = "Alphanumeric characters are required"
lblError.Show()
End If
End Sub
Screenshots
Invalid values
![Regular Expression (Regex) to accept only Alphanumeric (Alphabets and Numbers) in C# and VB.Net]()
![Regular Expression (Regex) to accept only Alphanumeric (Alphabets and Numbers) in C# and VB.Net]()
Valid Value
![Regular Expression (Regex) to accept only Alphanumeric (Alphabets and Numbers) in C# and VB.Net]()
Demo
![Regular Expression (Regex) to accept only Alphanumeric (Alphabets and Numbers) in C# and VB.Net]()
Downloads
