How to access string before encryption in c#

Hi all

     I am encrypting a password on client side. I want to access it before encryption. How to do that. Below is my code, how I am encrypting the password.

<script type="text/javascript" src="../js/md5.js"></script>  <script type="text/javascript">
       function GeneratePwd() {
           if (document.getElementById("txtpassword").value != "")
            {
                document.getElementById("txtDistance").value = document.getElementById("txtpassword").value;
               document.getElementById("txtpassword").value = hex_md5(document.getElementById("txtpassword").value);
           }
       }  </script> 

aspx

<asp:TextBox ID="txtpassword" runat="server" CssClass="mytextbox" TextMode="Password"></asp:TextBox>
<asp:RegularExpressionValidator ID="Regex2" runat="server" ControlToValidate="txtpassword"
                                ValidationExpression="^(?=.*[A-Za-z])(?=.*\d)(?=.*[$@$!%*#?&])[A-Za-z\d$@$!%*#?&]{8,}$"
                                ErrorMessage="Minimum 8 characters atleast 1 Alphabet, 1 Number and 1 Special Character"
                                ForeColor="Red" Display="Static" onpropertychange=" validateCheck()"></asp:RegularExpressionValidator><asp:Button ID="Button1" runat="server" onclick="Button1_Click" 
                            Text="Submit" />

code file

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            Button1.Attributes.Add("onclick", "return GeneratePwd();");
        }


     
    }

How can I achieve this?

I am doing this because after encryption the textbox get filled with the encrypted string and doesn't match with my RegularExpressionValidator. So I make a method in c# so that I can confirm the password complexity.

After encryption it is not possible to make RegularExpressionValidator  to work, because textbox is having encrypted string which doesn't meet myRegularExpressionValidator  requirement.