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| C# Regular Expression - Windows Form Application (Username Validation) |
private void txtUsername_TextChanged(object sender, EventArgs e)
{
if (IsValidUsername(txtUsername.Text))
{
lblMsg.ForeColor = System.Drawing.Color.Green;
lblMsg.Text = "Valid Username";
}
else
{
lblMsg.ForeColor = System.Drawing.Color.Red;
lblMsg.Text = "Invalid Username!";
}
}
public static bool IsValidUsername(string username)
{
//Username starts with a letter, allow letter or number, length between 7 to 12.
string pattern;
pattern = @"^[a-zA-Z][a-zA-Z0-9]{6,11}$";
Regex regex = new Regex(pattern);
return regex.IsMatch(username);
}