Alright I originally started out using a Convert.ToInt32(myradTextBox.Text) then it said specified cast is not valid. I did some research on here and decided to try Int.TryParse. Upon doing so I still received this error. What I am trying to do is when the user enters an ID and hits the create button, it searches the DB to see if that ID is already there. I have also tried to convert the bool value from my Int.TryParse to int using Convert.ToInt32(Result) still same error (see below in third code post for where that would be posted). Maybe it has something to do with my comparison method.
Below I have provided the Int.TryParse method with values. The Method I am calling to check the userinput is not in the db currently and my if statement that is catching the statement. Any input on how to fix this would be greatly appreciated. I am still new to most of this stuff so I apologize if leaving any critical info off. Just ask if you need clarification or something elaborated.
Here is my method for comparison:
public bool isValidID(int id)
{
SqlConnection dbConn = null;
int count = 0;
try
{
using (dbConn = new SqlConnection(Properties.Settings.Default["tville"].ToString()))
{
string sql = "SELECT Count(*) FROM PackLabelFormat where PackFormatID = #PackFormatID";
SqlCommand cmd = dbConn.CreateCommand();
cmd.CommandText = sql;
cmd.Parameters.AddWithValue("#PackFormatID", id);
dbConn.Open();
using (SqlDataReader reader = cmd.ExecuteReader())
{
reader.Read();
count = reader.GetInt16(0);
}
}
}
catch (Exception ex)
{
throw ex;
}
if (count > 0)
return false;
return true;
}
Here is my variables that I use in my Int.TryParse method:
string IDselect = rTxtBoxFormatID.Text.ToString();
int resultInt;
bool result = int.TryParse(IDselect, out resultInt);
Lastly here is my method that is catching the error:
SqlConnection dbConn = null;
LabelData labelList = new LabelData();
try
{
using (dbConn = new SqlConnection(Properties.Settings.Default["tville"].ToString()))
{
if (SelectedVersion.isValidID(resultInt))
{
SelectedVersion.PackFormatID = resultInt;
}
else
{
MessageBox.Show("ID already in use!", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
}
catch (Exception ex)
{
throw ex;
}
The database column did not support Int16 aka short. Which was why my specified cast is not valid error never went away no matter what I tried. Thank you for your help in this matter! Here is the code to further illustrate what the problem was.
using (SqlDataReader reader = cmd.ExecuteReader())
{
reader.Read();
//count = reader.GetInt16(0); needs to be reader.GetInt32(0);
}
Related
I have a discord bot that gets its data from a SQLite Database. I am using the System.Data.SQLite-Namespace
My problem is this code part:
m_dbConnection.Open();
SQLiteDataReader sqlite_datareader;
SQLiteCommand sqlite_cmd;
sqlite_cmd = m_dbConnection.CreateCommand();
sqlite_cmd.CommandText = SQLCommand; //SQLCommand is a command parameter
sqlite_datareader = sqlite_cmd.ExecuteReader();
while (sqlite_datareader.Read())
{
int i = 0;
while (true)
{
try
{
string temp = "";
try
{
temp = sqlite_datareader.GetString(i).ToString();
}
catch (Exception e)
{
Console.WriteLine(e.Message);
try
{
temp = sqlite_datareader.GetInt32(i).ToString();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
break;
}
}
output.Add(temp);
i++;
}
catch (Exception)
{
break;
}
}
}
For this example the variable SQLCommand is "SELECT Money FROM Users WHERE UserId = 12345 AND ServerID = 54321".
When I execute this command in an SQL Editor, , I get the value "10". So the command works. Now when I pass this command in my method, to get the data, I just got with the editor, I get the error Specified cast is not valid. at the code temp = sqlite_datareader.GetString(i).ToString();.
The value i is 0, to get the very first row that the sql command selected. I don't know why this happens, every other SQLite-Command works and gives me what I want. Why isn't this command working too?
Try using it this way
while (sqlite_datareader.Read())
{
for (int i = 0; i < reader.FieldCount; i++)
{
var ColName = reader.GetName(i);
var colValue = reader[i];
}
}
Please note that
while (sqlite_datareader.Read()){..}
the purpose of the above statement is to fetch all the rows.
therefore I would like to mention the problems in your code
1-) while(true){...}
is infinite loop, ofcourse in this scenario it would hit the break and quit but still this is not a good practice
2-) int i = 0;
you have declared and increased it by one inside the while loop. The problem here is that:
say you have 100 rows and 10 columns; this means that i would be increased to 99
however you have 10 colums, trying to get an invalid column value would give you an error
putting your code in try catch/ nested try catch statements would solve the issue however it's a nasty solution.
How do I store the results from a mysql query for use in other classes most efficiently?
I've tried the following code, which executes properly and stores all data in reader as it should. Reading the DataReader here works fine if I want to!
public class DatabaseHandler
{
public void MySqlGetUserByName(string input_username, MySqlDataReader reader)
{
try
{
_database.Open();
string query = "SELECT * FROM users WHERE username = '#input'";
MySqlParameter param = new MySqlParameter(); param.ParameterName = "#input"; param.Value = input_username;
MySqlCommand command = new MySqlCommand(query, _database);
command.Parameters.Add(param);
reader = command.ExecuteReader();
_database.Close();
}
catch(Exception ex)
{
Console.WriteLine(ex.ToString());
}
}
}
But when I try to read the same DataReader here, it is null and throws an exception (right after Debug6).
public class LoginHandler
{
public static void UserAuth(Client user, string input_username, string input_password)
{
DatabaseHandler dataBase = new DatabaseHandler();
MySqlDataReader dataReader = null;
dataBase.MySqlGetUserByName(input_username, dataReader);
Console.WriteLine("Debug6");
if (!dataReader.HasRows)
{
user.SendChatMessage("No match found.");
return;
}
while (dataReader.Read())
{
user.SetData("ID", (int)dataReader[0]);
user.SetData("username", (string)dataReader[1]);
user.SetData("email", (string)dataReader[2]);
user.SetData("password", (string)dataReader[3]);
}
dataReader.Close();
}
}
Please let me know how to make this work, or if there is a more efficient way of doing this without limiting the function of MySqlGetUserByName. The purpose of it is to input a name and a place to store all info from the match in the database.
Also, feel free to drop in any other suggestions that could make the code more efficient.
You could change your MySqlGetUserByName to return a User instance if all goes well, otherwise you return a null instance to the caller (Or you can thrown an exception, or you can set a global error flag in the DatabaseHandler class..., but to keep things simple I choose to return a null)
public class DatabaseHandler
{
public User MySqlGetUserByName(string input_username)
{
User result = null;
try
{
string query = "SELECT * FROM users WHERE username = #input";
using(MySqlConnection cnn = new MySqlConnection(......))
using(MySqlCommand command = new MySqlCommand(query, cnn))
{
cnn.Open();
command.Parameters.AddWithValue("#input", input_username);
using(MySqlDataReader dataReader = command.ExecuteReader())
{
if (dataReader.Read())
{
result = new User();
result.ID = Convert.ToInt32(dataReader[0]);
..... and so on with the other user properties ....
}
}
}
}
catch(Exception ex)
{
Console.WriteLine(ex.ToString());
}
// Return the user to the caller. If we have not found the user we return null
return result;
}
}
In the same way the caller handles the situation
public class LoginHandler
{
public static void UserAuth(string input_username, string input_password)
{
DatabaseHandler dataBase = new DatabaseHandler();
User result = dataBase.MySqlGetUserByName(input_username);
// If we have not found the user we have a null in the variable
if(result == null)
{
// Send your message using a static method in the user class
// User.SendMessage("User with username {input_username} not found!");
}
else
{
// User ok. return it? or do something with its data?
}
}
}
So this is a little bit code-ceptionlike.
I have a function that is checking the last ID in a table, this function is called within another function. At the end of that function, I have another function that's opening another datareader.
Error:
There is already an open Datareader associated with this connection which must be closed first.
getLastIdfromDB()
public string getLastIdFromDB()
{
int lastIndex;
string lastID ="";
var dbCon = DB_connect.Instance();
if (dbCon.IsConnect())
{
MySqlCommand cmd2 = new MySqlCommand("SELECT ID FROM `competitor`", dbCon.Connection);
try
{
MySqlDataReader reader = cmd2.ExecuteReader();
while (reader.Read())
{
string item = reader2["ID"].ToString();
lastIndex = int.Parse(item);
lastIndex++;
lastID = lastIndex.ToString();
}
}
catch (Exception ex)
{
MessageBox.Show("Error:" + ex.Message);
}
}
return lastID;
}
This function is later-on used in this function:
private void addPlayerBtn_Click(object sender, EventArgs e)
{
ListViewItem lvi = new ListViewItem(getLastIdFromDB());
.........................................^
... HERE
...
... irrelevant code removed
.........................................
var dbCon = DB_connect.Instance();
if (dbCon.IsConnect())
{
MySqlCommand cmd = new MySqlCommand("INSERT INTO `competitor`(`ID`, `Name`, `Age`) VALUES(#idSql,#NameSql,#AgeSql)", dbCon.Connection);
cmd.Parameters.AddWithValue("#idSql", getLastIdFromDB());
cmd.Parameters.AddWithValue("#NameSql", playerName.Text);
cmd.Parameters.AddWithValue("#AgeSql", playerAge.Text);
try
{
cmd.ExecuteNonQuery();
listView1.Items.Clear();
}
catch (Exception ex)
{
MessageBox.Show("Error:" + ex.Message);
dbCon.Connection.Close();
}
finally
{
updateListView();
}
}
}
What would be the best way for me to solve this problem and in the future be sure to close my connections properly?
UPDATE: (per request, included DB_connect)
class DB_connect
{
private DB_connect()
{
}
private string databaseName = "simhopp";
public string DatabaseName
{
get { return databaseName; }
set { databaseName = value; }
}
public string Password { get; set; }
private MySqlConnection connection = null;
public MySqlConnection Connection
{
get { return connection; }
}
private static DB_connect _instance = null;
public static DB_connect Instance()
{
if (_instance == null)
_instance = new DB_connect();
return _instance;
}
public bool IsConnect()
{
bool result = true;
try
{
if (Connection == null)
{
if (String.IsNullOrEmpty(databaseName))
result = false;
string connstring = string.Format("Server=localhost; database={0}; UID=root;", databaseName);
connection = new MySqlConnection(connstring);
connection.Open();
result = true;
}
}
catch (Exception ex)
{
Console.Write("Error: " + ex.Message);
}
return result;
}
public void Close()
{
connection.Close();
}
}
}
You are trying to have multiple open readers on the same connection. This is commonly called "MARS" (multiple active result sets). MySql seems to have no support for it.
You will have to either limit yourself to one open reader at a time, or use more than one connection, so you can have one connection for each reader.
My suggestion would be to throw away that singleton-like thingy and instead use connection pooling and proper using blocks.
As suggested by Pikoh in the comments, using the using clause indeed solved it for me.
Working code-snippet:
getLastIdFromDB
using (MySqlDataReader reader2 = cmd2.ExecuteReader()) {
while (reader2.Read())
{
string item = reader2["ID"].ToString();
lastIndex = int.Parse(item);
lastIndex++;
lastID = lastIndex.ToString();
}
}
Your connection handling here is not good. You need to ditch the DB_connect. No need to maintain a single connection - just open and close the connection each time you need it. Under the covers, ADO.NET will "pool" the connection for you, so that you don't actually have to wait to reconnect.
For any object that implements IDisposable you need to either call .Dispose() on it in a finally block, or wrap it in a using statement. That ensures your resources are properly disposed of. I recommend the using statement, because it helps keep the scope clear.
Your naming conventions should conform to C# standards. Methods that return a boolean should be like IsConnected, not IsConnect. addPlayerBtn_Click should be AddPlayerButton_Click. getLastIdFromDB should be GetlastIdFromDb or getLastIdFromDatabase.
public string GetLastIdFromDatabase()
{
int lastIndex;
string lastID ="";
using (var connection = new MySqlConnection(Configuration.ConnectionString))
using (var command = new MySqlCommand("query", connection))
{
connection.Open();
MySqlDataReader reader = cmd2.ExecuteReader();
while (reader.Read())
{
string item = reader2["ID"].ToString();
lastIndex = int.Parse(item);
lastIndex++;
lastID = lastIndex.ToString();
}
}
return lastID;
}
Note, your query is bad too. I suspect you're using a string data type instead of a number, even though your ID's are number based. You should switch your column to a number data type, then select the max() number. Or use an autoincrementing column or sequence to get the next ID. Reading every single row to determine the next ID and incrementing a counter not good.
I am using MySql 5.6x with Visual Studio 2015, windows 10, 64-bit. C# as programming language. In my CRUD.cs (Class file) i have created the following method:
public bool dbQuery(string sql,string[] paramList= null)
{
bool flag = false;
try
{
connect();
cmd = new MySqlCommand(sql,con);
cmd.Prepare();
if(paramList != null){
foreach(string i in paramList){
string[] valus = i.Split(',');
string p = valus[0];
string v = valus[1];
cmd.Parameters[p].Value = v;
}
}
if (cmd.ExecuteNonQuery() > 0)
{
flag = true;
}
}
catch (Exception exc)
{
error(exc);
}
}
I am passing the query and Parameters List like this:
protected void loginBtn_Click(object sender, EventArgs e)
{
string sql = "SELECT * FROM dept_login WHERE (user_email = ?user_email OR user_cell = ?user_cell) AND userkey = ?userkey";
string[] param = new string[] {
"?user_email,"+ userid.Text.ToString(),
"?user_cell,"+ userid.Text.ToString(),
"?userkey,"+ userkey.Text.ToString()
};
if (db.dbQuery(sql, param))
{
msg.Text = "Ok";
}
else
{
msg.Text = "<strong class='text-danger'>Authentication Failed</strong>";
}
}
Now the problem is that after the loop iteration complete, it directly jumps to the catch() Block and generate an Exception that:
Parameter '?user_email' not found in the collection.
Am i doing this correct to send params like that? is there any other way to do the same?
Thanks
EDIT: I think the best way might be the two-dimensional array to collect the parameters and their values and loop then within the method to fetch the parameters in cmd.AddWidthValues()? I may be wrong...
In your dbQuery you don't create the parameters collection with the expected names, so you get the error when you try to set a value for a parameter that doesn't exist
public bool dbQuery(string sql,string[] paramList= null)
{
bool flag = false;
try
{
connect();
cmd = new MySqlCommand(sql,con);
cmd.Prepare();
if(paramList != null){
foreach(string i in paramList){
string[] valus = i.Split(',');
string p = valus[0];
string v = valus[1];
cmd.Parameters.AddWithValue(p, v);
}
}
if (cmd.ExecuteNonQuery() > 0)
flag = true;
}
catch (Exception exc)
{
error(exc);
}
}
Of course this will add every parameter with a datatype equals to a string and thus is very prone to errors if your datatable columns are not of string type
A better approach would be this one
List<MySqlParameter> parameters = new List<MySqlParameter>()
{
{new MySqlParameter()
{
ParameterName = "?user_mail",
MySqlDbType= MySqlDbType.VarChar,
Value = userid.Text
},
{new MySqlParameter()
{
ParameterName = "?user_cell",
MySqlDbType= MySqlDbType.VarChar,
Value = userid.Text
},
{new MySqlParameter()
{
ParameterName = "?userkey",
MySqlDbType = MySqlDbType.VarChar,
Value = userkey.Text
},
}
if (db.dbQuery(sql, parameters))
....
and in dbQuery receive the list adding it to the parameters collection
public bool dbQuery(string sql, List<MySqlParameter> paramList= null)
{
bool flag = false;
try
{
connect();
cmd = new MySqlCommand(sql,con);
cmd.Prepare();
if(paramList != null)
cmd.Parameters.AddRange(paramList.ToArray());
if (cmd.ExecuteNonQuery() > 0)
{
flag = true;
}
}
catch (Exception exc)
{
error(exc);
}
}
By the way, unrelated to your actual problem, but your code doesn't seem to close and dispose the connection. This will lead to very nasty problems to diagnose and fix. Try to use the using statement and avoid a global connection variable
EDIT
As you have noticed the ExecuteNonQuery doesn't work with a SELECT statement, you need to use ExecuteReader and check if you get some return value
using(MySqlDataReader reader = cmd.ExecuteReader())
{
flag = reader.HasRows;
}
This, of course, means that you will get troubles when you want to insert, update or delete record where instead you need the ExecuteNonQuery. Creating a general purpose function to handle different kind of query is very difficult and doesn't worth the work and debug required. Better use some kind of well know ORM software like EntityFramework or Dapper.
Your SQL Commands' Parameters collection does not contain those parameters, so you cannot index them in this manner:
cmd.Parameters[p].Value = v;
You need to add them to the Commands' Parameters collection in this manner: cmd.Parameters.AddWithValue(p, v);.
My database is in SQL Server and I use Linq-to-SQL. I used from SP(Save cards) .
I put breakpoint in my code, when arrive at rdr = cmm.ExecuteReader(); get me exception!!!
private void btnSave_Click(object sender, EventArgs e)
{
PersianCalendar jc = new PersianCalendar();
string SaveDate = jc.GetYear(DateTime.Now).ToString();
int from=Convert.ToInt32(txt_barcode_f.Text);
int to=Convert.ToInt32(txt_barcode_t .Text);
int quantity=Convert.ToInt32(to-from);
int card_Type_ID=Convert.ToInt32(cmb_BracodeType .SelectedValue);
int[] arrCardNum = new int[quantity];
arrCardNum[0]=from;
for (int i = from; i < to;i++ )
{
for(int j=0; j<quantity ;j++)
{
arrCardNum[j]=from+j;
int r = arrCardNum[j];
sp.SaveCards(r, 2, card_Type_ID, SaveDate, 2);
}
}
}
public void SaveCards(int Barcode_Num, int Card_Status_ID, int Card_Type_ID, string Save_Date, int Save_User_ID)
{
IDbCommand cmm;
cmm = Linq.Connection.CreateCommand();
try
{
cmm.Parameters.Add(new SqlParameter("#Barcode_Num", Barcode_Num));
cmm.Parameters.Add(new SqlParameter("#Card_Status_ID", 2));
cmm.Parameters.Add(new SqlParameter("#Card_Type_ID", Card_Type_ID));
cmm.Parameters.Add(new SqlParameter("#SaveDate", Save_Date));
cmm.Parameters.Add(new SqlParameter("#Save_User_ID", Save_User_ID));
cmm.CommandText = "SaveCards";
cmm.Connection.Open();
cmm.Connection = Linq.Connection;
cmm.CommandType = CommandType.StoredProcedure;
IDataReader rdr = null;
**rdr = cmm.ExecuteReader();**
while (rdr.Read())
{
Console.Write(" All Insert ! " + "\n");
}
}
catch (SqlException ex)
{
SqlExceptionHandler(ex, Save_User_ID);
}
catch (Exception ex)
{
PopularEexceptionHandler(ex, Save_User_ID);
}
finally
{ cmm.Connection.Close(); }
}
when excute sp, show no result and display this:
when execute sp , display this:The INSERT statement conflicted with the CHECK constraint "CK_BarCode_Num". The conflict occurred in database "Parking", table "dbo.TBL_Cards", column 'BarCode_Num'. The statement has been terminated. No rows affected. (0 row(s) returned) #RETURN_VALUE = -6
You're a bit chaotic on how you set up your connection and command..... e.g. you open the connection before you even assign it! How is that going to work??
My recommendation would be this order (based on the principle first do all the setup before opening the connection, and furthermore open the connection as late as possible, close it as quickly as possible) :
IDbCommand cmm = Linq.Connection.CreateCommand();
try
{
// define name and type of command
cmm.CommandText = "SaveCards";
cmm.CommandType = CommandType.StoredProcedure;
// assign connection
cmm.Connection = Linq.Connection;
// define parameters
cmm.Parameters.Add(new SqlParameter("#Barcode_Num", Barcode_Num));
cmm.Parameters.Add(new SqlParameter("#Card_Status_ID", 2));
cmm.Parameters.Add(new SqlParameter("#Card_Type_ID", Card_Type_ID));
cmm.Parameters.Add(new SqlParameter("#SaveDate", Save_Date));
cmm.Parameters.Add(new SqlParameter("#Save_User_ID", Save_User_ID));
// only now - after all the setup - open the connection, read the data
cmm.Connection.Open();
IDataReader rdr = rdr = cmm.ExecuteReader();
while (rdr.Read())
{
....
}
}
To catch the errors that the execution throws, replace your catch block for the SqlException with this:
catch (SqlException ex)
{
StringBuilder sbErrors = new StringBuilder();
foreach (SqlError error in ex.Errors)
{
sbErrors.AppendLine(error.Message);
}
string allErrors = sbErrors.ToString();
}
and debug into that catch block - what is the allErrors string in the end??
Update: after a chat session, we know finally know what the message in the SQL exception is:
The INSERT statement conflicted with the CHECK constraint "CK_BarCode_Num". The conflict occurred in database "Parking", table "dbo.TBL_Cards", column 'BarCode_Num'.
Now we're trying to find out what that constraint is / does and why it gets violated....
I think it could be that you have open the connection and assigning another connection before executing the reader.
cmm.CommandText = "SaveCards";
//cmm.Connection.Open(); You should open the connection after assigning it
cmm.Connection = Linq.Connection;
cmm.CommandType = CommandType.StoredProcedure;
cmm.Connection.Open(); //Open it here
SqlDataReader rdr = cmm.ExecuteReader();