Validating Primary Key

Hello,

In my project , there is a column in the database which is primary key ,the value to this column will be given by user ,

The user should give the "int " value unique ,it should be validated on the client side itself 

I have used the following code :

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"
        ControlToValidate="TextBox3" ErrorMessage="Enter Your Faclty ID"
        ForeColor="#FF3300" Display="Dynamic">*</asp:RequiredFieldValidator><asp:CustomValidator ID="CustomValidator1" runat="server"
                    ControlToValidate="TextBox3"
                    ErrorMessage="Pls Pick Another Number" OnServerValidate="number" ></asp:CustomValidator><asp:SqlDataSource ID="SqlDataSource1" runat="server"
                    ConnectionString="<%$ ConnectionStrings:masterConnectionString12 %>"
                    SelectCommand="SELECT [Fid] FROM [Faculties]"></asp:SqlDataSource><asp:Label ID="Label9" runat="server"></asp:Label>

  protected void number(object source, ServerValidateEventArgs args)
    {
        int fid = Convert.ToInt32(TextBox3.Text);
        args.IsValid = true;
        foreach (DataRowView drv in SqlDataSource1.Select(DataSourceSelectArguments.Empty))
        {
            if (drv ["Fid"].ToString() == args.Value.ToString())
            {
                args.IsValid = false;
                break;
            }
        }

        if (args.IsValid)
            Label9.Text = "Congratulations! That id is not taken.";
    }

But it is not working .....

It's urgent could you pls help me out ...