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C# MySQLDataReader returns column names instead of field values

I am using MySQLClient with a local database. I wrote a method which returns a list of data about the user, where I specify the columns I want the data from and it generates the query dynamically.
However, the reader is only returning the column names rather than the actual data and I don't know why, since the same method works previously in the program when the user is logging in.
I am using parameterised queries to protect from SQL injection.
Here is my code. I have removed parts which are unrelated to the problem, but i can give full code if needed.
namespace Library_application
{
class MainProgram
{
public static Int32 user_id;
static void Main()
{
MySqlConnection conn = LoginProgram.Start();
//this is the login process and works perfectly fine so i won't show its code
if (conn != null)
{
//this is where things start to break
NewUser(conn);
}
Console.ReadLine();
}
static void NewUser(MySqlConnection conn)
{
//three types of users, currently only using student
string query = "SELECT user_role FROM Users WHERE user_id=#user_id";
Dictionary<string, string> vars = new Dictionary<string, string>
{
["#user_id"] = user_id.ToString()
};
MySqlDataReader reader = SQLControler.SqlQuery(conn, query, vars, 0);
if (reader.Read())
{
string user_role = reader["user_role"].ToString();
reader.Close();
//this works fine and it correctly identifies the role and creates a student
Student user = new Student(conn, user_id);
//later i will add the logic to detect and create the other users but i just need this to work first
}
else
{
throw new Exception($"no user_role for user_id - {user_id}");
}
}
}
class SQLControler
{
public static MySqlDataReader SqlQuery(MySqlConnection conn, string query, Dictionary<string, string> vars, int type)
{
MySqlCommand cmd = new MySqlCommand(query, conn);
int count = vars.Count();
MySqlParameter[] param = new MySqlParameter[count];
//adds the parameters to the command
for (int i = 0; i < count; i++)
{
string key = vars.ElementAt(i).Key;
param[i] = new MySqlParameter(key, vars[key]);
cmd.Parameters.Add(param[i]);
}
//runs this one
if (type == 0)
{
Console.WriteLine("------------------------------------");
return cmd.ExecuteReader();
//returns the reader so i can get the data later and keep this reusable
}
else if (type == 1)
{
cmd.ExecuteNonQuery();
return null;
}
else
{
throw new Exception("incorrect type value");
}
}
}
class User
{
public List<string> GetValues(MySqlConnection conn, List<string> vals, int user_id)
{
Dictionary<string, string> vars = new Dictionary<string, string> { };
//------------------------------------------------------------------------------------
//this section is generating the query and parameters
//using parameters to protect against sql injection, i know that it ins't essential in this scenario
//but it will be later, so if i fix it by simply removing the parameterisation then im just kicking the problem down the road
string args = "";
for (int i = 0; i < vals.Count(); i++)
{
args = args + "#" + vals[i];
vars.Add("#" + vals[i], vals[i]);
if ((i + 1) != vals.Count())
{
args = args + ", ";
}
}
string query = "SELECT " + args + " FROM Users WHERE user_id = #user_id";
Console.WriteLine(query);
vars.Add("#user_id", user_id.ToString());
//-------------------------------------------------------------------------------------
//sends the connection, query, parameters, and query type (0 means i use a reader (select), 1 means i use non query (delete etc..))
MySqlDataReader reader = SQLControler.SqlQuery(conn, query, vars, 0);
List<string> return_vals = new List<string>();
if (reader.Read())
{
//loops through the reader and adds the value to list
for (int i = 0; i < vals.Count(); i++)
{
//vals is a list of column names in the ame order they will be returned
//i think this is where it's breaking but im not certain
return_vals.Add(reader[vals[i]].ToString());
}
reader.Close();
return return_vals;
}
else
{
throw new Exception("no data");
}
}
}
class Student : User
{
public Student(MySqlConnection conn, int user_id)
{
Console.WriteLine("student created");
//list of the data i want to retrieve from the db
//must be the column names
List<string> vals = new List<string> { "user_forename", "user_surname", "user_role", "user_status"};
//should return a list with the values in the specified columns from the user with the matching id
List<string> return_vals = base.GetValues(conn, vals, user_id);
//for some reason i am getting back the column names rather than the values in the fields
foreach(var v in return_vals)
{
Console.WriteLine(v);
}
}
}
What i have tried:
- Using getstring
- Using index rather than column names
- Specifying a specific column name
- Using while (reader.Read)
- Requesting different number of columns
I have used this method during the login section and it works perfectly there (code below). I can't figure out why it doesnt work here (code above) aswell.
static Boolean Login(MySqlConnection conn)
{
Console.Write("Username: ");
string username = Console.ReadLine();
Console.Write("Password: ");
string password = Console.ReadLine();
string query = "SELECT user_id, username, password FROM Users WHERE username=#username";
Dictionary<string, string> vars = new Dictionary<string, string>
{
["#username"] = username
};
MySqlDataReader reader = SQLControler.SqlQuery(conn, query, vars, 0);
Boolean valid_login = ValidLogin(reader, password);
return (valid_login);
}
static Boolean ValidLogin(MySqlDataReader reader, string password)
{
Boolean return_val;
if (reader.Read())
{
//currently just returns the password as is, I will implement the hashing later
password = PasswordHash(password);
if (password == reader["password"].ToString())
{
MainProgram.user_id = Convert.ToInt32(reader["user_id"]);
return_val = true;
}
else
{
return_val = false;
}
}
else
{
return_val = false;
}
reader.Close();
return return_val;
}

The problem is here:
string args = "";
for (int i = 0; i < vals.Count(); i++)
{
args = args + "#" + vals[i];
vars.Add("#" + vals[i], vals[i]);
// ...
}
string query = "SELECT " + args + " FROM Users WHERE user_id = #user_id";
This builds a query that looks like:
SELECT #user_forename, #user_surname, #user_role, #user_status FROM Users WHERE user_id = #user_id;
Meanwhile, vars.Add("#" + vals[i], vals[i]); ends up mapping #user_forename to "user_forename" in the MySqlParameterCollection for the query. Your query ends up selecting the (constant) value of those parameters for each row in the database.
The solution is:
Don't prepend # to the column names you're selecting.
Don't add the column names as variables to the query.
You can do this by replacing that whole loop with:
string args = string.Join(", ", vals);

How to convert Handsontable data back into C# class

I am using an ajax post to send my column headers and data from a handsontable back to an ashx handler.
$.ajax({
type: 'POST',
url: "Scripts/SaveExcelData.ashx",
contentType: "application/json; charset=utf-8",
data: JSON.stringify({"columns": hot.getColHeader(), "rows": hot.getData()}),
success: function (data) {}
});
Currently I am using to following to deserialize the request, but have not been able to successfully come up with anything that converts the rows into an array of DataBaseRow class objects.
var jsonString = String.Empty;
context.Request.InputStream.Position = 0;
using (var inputStream = new StreamReader(context.Request.InputStream))
{
jsonString = inputStream.ReadToEnd();
var results = JsonConvert.DeserializeObject<dynamic>(jsonString);
var columns = results.columns;
var rows = results.rows;
//use columns here to convert rows into DataBaseRow class
}
columns looks like: {["Col1","Col2","Col3"]}
rows looks like: {[["Val1","Val2","Val3"],["Val1","Val2","Val3"],["Val1","Val2","Val3"]]}
How can I do this?
UPDATE
Instead of trying to convert the dynamic class into the DataBaseRow class, I found I could actually just manually loop through the array values and write them into new instances of the DataBaseRow class.
using (DBEntities edmx = new DBEntities())
{
foreach (var row in rows)
{
DataBaseRow dbr = new DataBaseRow();
edmx.DataBaseRow.Add(dbr);
dbr.LoadedTime = DateTime.Now;
for (int i = 0; i < row.Count; i++)
{
string colval = row[i].ToString();
string colname = columns[i].ToString();
switch (colname)
{
case "Col1":
dbr.DBCol1 = colval;
break;
case "Col2":
dbr.DBCol2 = colval;
break;
case "Col3":
dbr.DBCol3 = colval;
break;
}
}
}
edmx.SaveChanges();
}
This works, but is very slow (see comment for timings). Is there a faster/better way to process this data? (if it matters - I actually have 14 columns that I'm mapping in the switch)

So the technical answer to my question can be found in the Update I added (just reference the dynamic objects as arrays, don't try to convert them).
However, seems like Entity Framework is very poor at handling saving large datasets. This can be sped up by grouping the saves into chunks and recreating the context for every chunck. https://stackoverflow.com/a/5942176/266592
I ended up rewriting this to insert the values into a DataTable and then using SqlBulkCopy to save the records to the database.
var jsonString = String.Empty;
context.Request.InputStream.Position = 0;
using (var inputStream = new StreamReader(context.Request.InputStream))
{
jsonString = inputStream.ReadToEnd();
var results = JsonConvert.DeserializeObject<dynamic>(jsonString);
var columns = results.columns;
var rows = results.rows;
var dt = new DataTable();
for (int i = 0; i < columns.Count; i++)
{
dt.Columns.Add(columns[i].ToString());
}
foreach (var row in rows)
{
var datarow = dt.NewRow();
for (int i = 0; i < row.Count; i++)
{
datarow[i] = row[i];
}
dt.Rows.Add(datarow);
}
using (var connection = new SqlConnection(ConnectionString))
{
SqlTransaction transaction = null;
connection.Open();
try
{
transaction = connection.BeginTransaction();
using (var sqlBulkCopy = new SqlBulkCopy(connection, SqlBulkCopyOptions.TableLock, transaction))
{
sqlBulkCopy.DestinationTableName = "TABLENAME";
sqlBulkCopy.BatchSize = 100000;
sqlBulkCopy.BulkCopyTimeout = 0;
foreach (DataColumn col in dt.Columns)
{
sqlBulkCopy.ColumnMappings.Add(col.ColumnName, col.ColumnName);
}
sqlBulkCopy.WriteToServer(dt);
}
transaction.Commit();
}
catch (Exception)
{
transaction.Rollback();
}
}
}

Use AJAX to send array of JavaScript objects to database

In this project the user will have the opportunity to create an array of objects with properties and those properties match up with a database table, with the properties of the object being the same as the columns in the database cable. The SQL looks like:
create table ServiceData
(ServiceId int
,ServiceDescription varchar(50)
)
go
create type ServiceType as table
(ServiceId int
,ServiceDescription varchar(50)
)
go
create proc spInsertService
#service ServiceType readonly
as
begin
insert into ServiceData(ServiceId,ServiceDescription)
select * from #service
end
Here I create a custom type and pass that custom type to a stored procedure in the form of a table valued parameter. The SQL and the following C# code execute and work fine:
[WebMethod]
public void InsertServiceData()
{
List<ServiceData> sdList = new List<ServiceData>();
ServiceData sd1 = new ServiceData(1, "first");
ServiceData sd2 = new ServiceData(2, "second");
sdList.Add(sd1);
sdList.Add(sd2);
DataTable dt = new DataTable();
dt.Columns.Add("ServiceId");
dt.Columns.Add("ServiceDescription");
foreach (var data in sdList)
{
dt.Rows.Add(data.ServiceId, data.ServiceDescription);
}
string cs = ConfigurationManager.ConnectionStrings["dbcs"].ConnectionString;
using (var con = new SqlConnection(cs))
{
using (var cmd = new SqlCommand("spInsertService",con))
{
con.Open();
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("#service", dt);
cmd.ExecuteNonQuery();
}
}
}
You can see that in this working example I'm not using any AJAX call to send data to the web method. This code currently works and inserts the data from that hardcoded list fine. So when I change the code to actually try to take a JavaScript array like so:
$(document).ready(function ()
{
sd1 = {};
sd1.ServiceId = 1;
sd1.ServiceDescription = "test";
sd2 = {};
sd2.ServiceId = 2;
sd2.ServiceDescription = "other test";
//create array which is meant to mirror the List<ServiceData> in the
//earlier example
service = new Array();
service.push(sd1);
service.push(sd2);
//wrap the array in a data transfer object
var dto = {'sdList': service};
$('#btnSubmit').click(function ()
{
$.ajax(
{
type: "POST",
url: "WebService.asmx/InsertServiceData",
contentType: "application/json",
dataType: "json",
//stringify the dto
data: JSON.stringify(dto),
success: function(data)
{
console.log('success');
},
error: function(thrownError)
{
console.log(thrownError);
}
});
});
});
new C#
[WebMethod]
//this attempts to deserialize the DTO into a list of ServiceData objects
//which are then inserted into the TVP and then to the database
public void InsertServiceData(string sdList)
{
var jss = new JavaScriptSerializer();
List<ServiceData> list = jss.Deserialize<List<ServiceData>>(sdList);
DataTable dt = new DataTable();
dt.Columns.Add("ServiceId");
dt.Columns.Add("ServiceDescription");
foreach (var data in list)
{
dt.Rows.Add(data.ServiceId, data.ServiceDescription);
}
string cs = ConfigurationManager.ConnectionStrings["dbcs"].ConnectionString;
using (var con = new SqlConnection(cs))
{
using (var cmd = new SqlCommand("spInsertService",con))
{
con.Open();
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("#service", dt);
cmd.ExecuteNonQuery();
}
}
}
Currently that code gives me the error: Type\u0027System.String\u0027isnotsupportedfordeserializationofanarray
If I don't wrap the array in a DTO object, but still stringify it I get
`System.Collections.Generic.IDictionary`2[[System.String,mscorlib,Version=4.0.0.0,Culture=neutral,PublicKeyToken`
I would like to not have to use SessionState of ViewState for this. Since I know the code works fine if I'm not passing a JavaScript array to the WebMethod, it has to been somewhere in the serialization and deserialization of the array that's breaking it. How can I fix this? It's been driving me nuts for days now

Please note following steps and then change your code lines.
Dont create sd1={} and sd2{}.
Create var list = []; at top then push json object like list.push({"ServiceId":1,"ServiceDescription":"test"}, {"ServiceId":2,"ServiceDescription":"other test"})
Create ajax parameter like var data = "{'sdLists':" +JSON.stringify(list)+"}"; and pass date as param.
Create a bean with variables to map json object as added in list above. see blow.
public class SdList{
private int Serviceid;
public int Serviceid
{
get { return Serviceid; }
set { Serviceid= value; }
}
private string ServiceDescription;
public string ServiceDescription
{
get { return ServiceDescription; }
set { ServiceDescription= value; }
}
}
Now Pass List<SdList> sdLists as parameter list to method as under
var data = "{'sdLists':"+JSON.stringify(list)+"}";
public void InsertServiceData(List sdLists)
Then Convert Json List in to generic list using java script serializer as under,
JavaScriptSerializer jss= new JavaScriptSerializer();
List<SdList> list = jss.ConvertToType<List<SdList>>(sdLists);
I have followed above steps and it is working fine.

XML Field in SQL

I have a method which serializes an object, into a SQL Server XML field. I see the XML in SQL server in Managmenet Studio, and now I need to display that in a HTML page.
I use an AJax function calling into a WebMethod, which calls a stored procedure as follows:
using (conn){
using (SqlCommand cmd = new SqlCommand()){
conn.Open();
cmd.CommandText = "GetMessage_Sel";
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add("#messageId", SqlDbType.VarChar, 50).Value = str;
cmd.Connection = conn;
try{
rdr = cmd.ExecuteReader();
if (rdr.HasRows){
while (rdr.Read()){
returnValue1 = rdr.GetString(0);
returnValue2 = rdr.GetString(1);
}
}
else{
Console.WriteLine("No rows found.");
}
rdr.Close();
}
catch (Exception err){
// handle the error
//messageInsert = false;
}
finally{
conn.Close();
}
}
}
return new string[] {returnValue1,returnValue2};
the ajax is therefore set up as follows:
$('.view-details').click(function (e) {
e.preventDefault();
$('#ticket-id').text("Ticket id: " + $(this).closest('tr').children().eq(1).html());
$.ajax({
type: "POST",
url: "Default.aspx/PopulatePopUp",
cache: false,
data: "{'arg':'" + $(this).closest('tr').children().eq(1).html() + "'}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function (msg)
{
$("#CompleteMessage").text(msg.d[0]);
$("#lblaka").text(msg.d[1]);
}
});
}
so #lblaka displays the entire XML message, but i need to break this down into a more readable manner. So eithe in my WebMethod or the Ajax function, how do i iterate through the rdr.GetString(1), so something like this
foreach (var item in rdr.GetString(1)) {
string 1 = xml node value 1 ..... etc
}
EDIT:
Here is an example of the XML being stored.
<Person xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<AKA>
<string>Name 1</string>
<string>Name 2</string>
</AKA>
<Countries>
<string>USA</string>
<string>UK</string>
</Countries>
<Names>
<string>Name 1</string>
<string>Name 2</string>
</Names>
<Gender>Male</Gender>
</Person>

Here is how you could do it with jQuery:
declare this function:
function GetNestedElements(aThis, name) {
$(aThis).find(name).each(function(index){
$("#lblaka").append('<span>'+ name +' : ');
$(this).find('string').each(function(index){
$("#lblaka").append($(this));
});
$("#lblaka").append('</span><br/>');
});
}
Use this in your success call:
var xml = $.parseXML(msg),
$xml = $( xml );
$xml.find('Person').each(function(index){
GetNestedElements(this, 'AKA');
GetNestedElements(this, 'Countries');
GetNestedElements(this, 'Names');
var gender = $(this).find('Gender').text();
$("#lblaka").append('<span>Gender : ' + gender + '</span><br/>');
});
Please see this jsFiddle for a working version (select 'Show Person' to view it):
http://jsfiddle.net/MZ5Xs/2/

If its pure XLM in your SQL string you could load the string into and XDocument like so and query using linq to get your list to loop over.
XDocument xDoc = XDocument.Parse(rdr.GetString(1));
var query = xDoc.Descendants("AKA").Elements("string").ToList();
//If you want to add them to an Array
string[] array = new string[query.Count() -1];
int i = 0
// this will add the values Name 1 and Name 2 to an array
foreach (var element in query)
{
array[i] = element.Value;
i++;
}

jQuery AJAX postback to WebMethod returning only first row of results

I have the following JQUERY code that I'm expecting to return 3 json results to the console. What's happening is I'm getting 3 copies of the results of the first return.
so for example I'm trying to see filename's, and I'm getting back "first name, first name, first name" instead of "first name, second name, third name"
here's my code:
$.ajax({
type: "POST",
url: "front.aspx/GetData",
data: "{}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function (msg) {
var obj = msg.d;
$.each(obj, function(index, value){
console.log(value);
});
}
});
what am I doing wrong with the each function?
I don't think you need my CS code to tell me what I'm doing wrong, but incase you do, here it is:
public class LoadData {
public string filename;
public string date;
public string filetype;
public Int32 height;
public Int32 width;
public string uploadGroup;
public string title;
public string uniqueID;
public string uploader;
public string uniqueIDnoExt;
}
[WebMethod]
public static List<LoadData> GetData() {
LoadData b = new LoadData();
List<LoadData> info = new List<LoadData>();
SqlDataReader reader;
string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ToString();
SqlConnection connection = new SqlConnection(connectionString);
connection.Open();
SqlCommand command = new SqlCommand("SELECT * FROM uploads ORDER BY id DESC", connection);
command.Parameters.Add(new SqlParameter("uploader", "anonymous"));
reader = command.ExecuteReader();
while (reader.Read()) {
b.filename = reader.GetString(1);
b.date = reader.GetSqlDateTime(3).ToString();
b.filetype = reader.GetString(4);
b.height = (Int32)reader.GetSqlInt32(5);
b.width = (Int32)reader.GetSqlInt32(6);
b.uploadGroup = reader.GetString(7);
b.title = reader.GetString(8);
b.uniqueID = reader.GetString(9);
b.uploader = reader.GetString(10);
b.uniqueIDnoExt = reader.GetString(12);
info.Add(b);
}
return info;
}

Move this line
LoadData b = new LoadData();
inside the loop.
while (reader.Read()) {
LoadData b = new LoadData();
b.filename = reader.GetString(1);
b.date = reader.GetSqlDateTime(3).ToString();
b.filetype = reader.GetString(4);
b.height = (Int32)reader.GetSqlInt32(5);
b.width = (Int32)reader.GetSqlInt32(6);
b.uploadGroup = reader.GetString(7);
b.title = reader.GetString(8);
b.uniqueID = reader.GetString(9);
b.uploader = reader.GetString(10);
b.uniqueIDnoExt = reader.GetString(12);
info.Add(b);
}
The way you have it now you make only one line of data. The List<> holds the reference, it does not recreate them. So if you're not making new data, you're not inserting any new data (as it is now). You're just adding first one in memory, and then changing the values.
Also you can read :
http://en.wikipedia.org/wiki/Linked_list
By the way.
You have left open many things, you will soon end up without resources. Use the using keyword on the objects that need to be closed. And, for speed, use a static string (to read only) on the connection string.

You are creating list in wrong way.. Follow #Aristos way to add object correctly.
and at your ajax request sucess: section..
Loop Throuh d.data. Check this JQuery Ajax with Class Arrays
for (var i in d.data) { }
And you can Manually convert result dataset to JSON