Validations using Regular Expressions

< form id="form1" runat="server" >
 < div >
   < fieldset  style="width:50%" >
     < legend > Finding Number using RegularExpressions < /legend >
       < table >
          < tr >
            < td > String containing Number: < asp:TextBox ID="txtText" runat="server" > < /asp:TextBox > < /td >            
          < /tr >
          < tr >
            < td > < asp:Button ID="btnFind" Text="Find Number" runat="server" onclick="btnFind_Click" /> </td > 
          </tr >
          < tr >
            < td > < asp:Label ID="lblResults" runat="server" > < /asp:Label > < /td >
          < /tr >
      < /table >     
  < /fieldset > 
    
  < fieldset  style="width:50%" >
    < legend > Validations using RegularExpressions </legend >
      < table >
          < tr >
            < td > Zip Code: < asp:TextBox ID="txtZipCode" runat="server" > </asp:TextBox > (A 5-digit or 5+4 digit zip code.)   

          < /td >            
          < /tr >
           < tr >
            < td > Date: < asp:TextBox ID="txtDate" runat="server" > < /asp:TextBox > (Date in mm-dd-yyyy or mm-dd-yy format) < /td >            
          < /tr >
           < tr >
            < td > Email: < asp:TextBox ID="txtEmail" runat="server" > </asp:TextBox> </td >            
          < /tr >
          < tr >
            < td > < asp:Button ID="btnValidate" Text="Validate" runat="server" 
                    onclick="btnValidate_Click"/> </td > 
          < /tr>
          < tr >
            < td > < asp:Label ID="lblValidate" runat="server" > </asp:Label > </td >
          < /tr >
     < /table >     
   < /fieldset >    
 < /div >
< /form >

using System.Text.RegularExpressions;

protected void btnFind_Click(object sender, EventArgs e)
{              
    Match mtch = Regex.Match(txtText.Text, @"\d+");
        
    if (mtch.Success) 
    {
       
       //It will find the number's position in the given string ex:abc123abc - it finds 1 at 3rd position
       
       lblResults.Text = string.Format("RegEx found " + mtch.Value + " at position " + mtch.Index.ToString());
    }
    else 
    {
       lblResults.Text = "You didn't enter a string containing a number!";
    }
}

protected void btnValidate_Click(object sender, EventArgs e)
{
    bool IsValid = true;

    
    // Zip Code validation
    
    if (!Regex.IsMatch(txtZipCode.Text, @"^\s*(\d{5}|(\d{5}-\d{4}))\s*$"))
    {
       txtZipCode.ForeColor = Color.Red;
       IsValid = false;
    }
    else
    {
       txtZipCode.ForeColor = Color.Black;
    }


     
     //Date validation
     
     if (!Regex.IsMatch(txtDate.Text, @"^\s*\d{1,2}(/|-)\d{1,2}\1(\d{4}|\d{2})\s*$"))
     {
       txtDate.ForeColor = Color.Red;
       IsValid = false;
     }
     else
     {
       txtDate.ForeColor = Color.Black;
     }

     
     // email validation
     
     if (!Regex.IsMatch(txtEmail.Text, @"^([\w-]+\.)*?[\w-]+@[\w-]+\.([\w-]+\.)*?[\w]+$"))
     {
        txtEmail.ForeColor = Color.Red;
        IsValid = false;
     }
     else
     {
       txtEmail.ForeColor = Color.Black;
     }
}