Question

I want to access data and show in label ajax page methods but data is not displaying.

PageMethods.GetDataFromDB(OnSucceeded, OnFailed);
         //}
        function OnSucceeded(result, userContext, methodName) {
            var jsonData = eval(result.d);
            $get('Label1').innerHTML = jsonData.FirstName;
        }    
 [WebMethod]
    public static string GetDataFromDB()
    {
        System.Collections.Generic.Dictionary<string, string> DictionaryGetPerson = new Dictionary<string, string>();
        using (OracleConnection con = new OracleConnection("server=xe; uid=system; pwd=;"))
        {
            string Command = "Select * from tblSavePerson";                //selecting Top 1 Row in Oracle
            OracleCommand cmd = new OracleCommand(Command, con);
            con.Open();
            OracleDataReader dr = cmd.ExecuteReader();
            while (dr.Read())
            {
                DictionaryGetPerson.Add("FirstName",dr["FirstName"].ToString());

            }
        }
        JavaScriptSerializer js = new JavaScriptSerializer();
       return js.Serialize(DictionaryGetPerson).ToString();

}

table has only one row.

Answer 1

Since you have given the tags as jQuery and jQuery Ajax I am deviating a little from the solution.

Do these things

1.Wrap your WebMethod in a try-catch block. try-catch are there for a reason.

[WebMethod]
public static string GetDataFromDB()
{
    try
    {
        System.Collections.Generic.Dictionary<string, string> DictionaryGetPerson = new Dictionary<string, string>();
        using (OracleConnection con = new OracleConnection("server=xe; uid=system; pwd=;"))
        {
            string Command = "Select * from tblSavePerson";                //selecting Top 1 Row in Oracle
            OracleCommand cmd = new OracleCommand(Command, con);
            con.Open();
            OracleDataReader dr = cmd.ExecuteReader();
            while (dr.Read())
            {
                DictionaryGetPerson.Add("FirstName", dr["FirstName"].ToString());

            }
        }
        JavaScriptSerializer js = new JavaScriptSerializer();
        return js.Serialize(DictionaryGetPerson).ToString();
    }
    catch (Exception exception)
    {
        //Elmah.ErrorSignal.FromCurrentContext().Raise(exception);
        throw new Exception(exception.Message);
    }
}

Please note that this Dictionary will fail with Duplicate Key error if you have more than one row. If there are no errors lets move to step 2.

2.Do not use PageMethods.GetDataFromDB. It very ancient. Using jQuery one can consume ASP.NET Ajax Page Methods directly. Call Page method like this.

function LoadNames() {
    $.ajax({
        contentType: "application/json;",
        data: "{}",
        type: "POST",
        url: 'Test1.aspx/GetDataFromDB',
        success: function (msg) {
            OnSucceeded(msg);
        },
        error: function (xhr, status, error) {
            //alert("error");
            //OnFailed(a, b, c);
        }
    });
}

function OnSucceeded(dict) {
    var jsonData = dict.hasOwnProperty("d") ? dict.d : dict;
    var json = $.parseJSON(jsonData);
    alert(json.FirstName);

}

Also, don’t eval(result.d) when we have $.parseJSON in jQuery.

Hope this helps.