check duplicate value entry in grid view

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;

public partial class Register : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
[System.Web.Services.WebMethod]
public static string CheckUserName(string args)
{
    string returnValue = string.Empty;
    string conString = ConfigurationManager.ConnectionStrings["conn"].ConnectionString;
    SqlConnection sqlConn = new SqlConnection(conString);
    try
    {
        SqlCommand sqlCmd = new SqlCommand("CheckUserName", sqlConn);
        sqlCmd.CommandType = CommandType.StoredProcedure;
        sqlCmd.Parameters.AddWithValue("@empcode", args.Trim());
        sqlConn.Open();
        int success = int.Parse((sqlCmd.ExecuteScalar().ToString()));
        if (success == 1) // User Name Not Available
        {
            returnValue = "'" + args + "' is already in use.";

        }
        else if (success == 0)//User_Name is available
        {
            returnValue = "Available";
        }
    }
    catch
    {
        //Handle Error
    }
    finally
    {
        sqlConn.Close();
    }

    return returnValue;
}

}