I'm getting the error:
Invalid attempt to access a field before calling Read()
at: string result = Reader.GetString(0);
I'm not entirely sure what to do or whats wrong though
internal int GetCharGuidByName(string charactername, MySqlConnection connection)
{
MySqlCommand command = connection.CreateCommand();
MySqlDataReader Reader;
command.CommandText = "SELECT guid FROM characters WHERE name=\""+charactername+"\";";
// Initialize MySQL Reader
Reader = command.ExecuteReader();
Reader.Read();
string result = Reader.GetString(0);
// If the character doesn't exist or isn't entered, return 0
int charguid = 0;
if (result != String.Empty)
{
charguid = Convert.ToInt32(result);
}
return charguid;
}
Change the code to:
Reader = command.ExecuteReader();
int charguid = 0;
if(Reader.Read())
{
if(Reader[0] != DBNull.Value)
{
if(int.TryParse(Reader[0].ToString(), out charguid))
{
//value read and is an integer!
}
}
}
return charguid;
You should use ExecuteScalar instead of ExecuteReader
ExecuteSaclar returns the first column of the first row in the result
set, or a null reference
ExecuteReader will return as resultset which you have to then iterate
to read
So looking at your code you just want the first column of the result set
internal int GetCharGuidByName(string charactername, MySqlConnection connection)
{
int charguid = 0;
using(MySqlCommand command = connection.CreateCommand())
{
command.CommandText = "SELECT guid FROM characters WHERE name=\""+charactername+"\";";
object obj = command.ExecuteScalar();
if (obj != null && obj != DBNull.Value)
{
charguid = Convert.ToInt32(obj);
}
}
return charguid;
}
openConnection()
sql = "SELECT last, first, emp_type, active FROM employee INNER JOIN account ON employee.emp_id = account.emp_id WHERE employee.emp_id = '" & AtxtEmpID.Text & "'"
command = New MySqlCommand(sql, mySqlConnection)
reader = command.ExecuteReader
reader.Read()
AtxtEmpName.Text = reader.Item(0) & ", " & reader.Item(1)
closeConn()
have the save problem
Related
Have the error 'dbConn.ServerVersion' threw an exception of type 'System.InvalidOperationException, however VisualStudio does not pause the program and throw the exception at me. Here is the code:private void BTN_NA_Click(object sender, EventArgs e)
{
if (TXT_NAUN.Text != "" && TXT_NAPW.Text != "" && TXT_NAPW2.Text != "")
{
if (TXT_NAPW.Text == TXT_NAPW2.Text)
{
string input = TXT_NAPW.Text;
int hash = 0;
int output = 0;
foreach (char chara in input)
{
int temp = 0;
temp = System.Convert.ToInt32(chara);
output = output + temp;
output = output * 2;
}
hash = output % 1000;
OleDbConnection dbConn = new System.Data.OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=BHShooterProjectDB.accdb");
string sql = "SELECT Accounts.PlayerID FROM Accounts ORDER BY Accounts.PlayerID DESC ";
///string comm = "SELECT Accounts.PlayerID from Accounts";
/// INNER JOIN Leaderboard ON Leaderboard.PlayerID = Accounts.PlayerID WHERE Accounts.PlayerUsername = #ip";
OleDbCommand cmd = new OleDbCommand(sql, dbConn);
string result = "";
dbConn.Open();
OleDbDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
result = reader[0].ToString();
}
dbConn.Close();
{
string comm = "INSERT INTO Accounts (PlayerUsername, PlayerPassword, PlayerID, PlayerInvID) VALUES (#NAUN, #HPW, #NAPI, #NAPI)";
OleDbCommand command = new OleDbCommand(comm, dbConn);
command.Parameters.AddWithValue("#NAUN", TXT_NAUN.Text);
command.Parameters.AddWithValue("#HPW", hash);
foreach (char chara in result)
{
int temp = 0;
temp = System.Convert.ToInt32(chara);
result = result + temp;
}
result = result + 1;
command.Parameters.AddWithValue("#NAPI", result);
command.Parameters.AddWithValue("#NAPI", result);
dbConn.Open();
int rowsAffected = cmd.ExecuteNonQuery(); ///error appears here
dbConn.Close();
}
}
}
}
Any suggestions on solution, have tried a lot and this is my last hope!
Thanks,
Blackclaw_
At the line you got the error, you are using cmd (the select command). I think you want to use command (the insert command).
I want to check if a SQL job is currently running. Is the "run_status" column the correct one to check? Is there a simpler way of doing this without having to loop through each column?
public int CheckAgentJob(string connectionString, string jobName)
{
SqlConnection dbConnection = new SqlConnection(connectionString);
SqlCommand command = new SqlCommand();
command.CommandType = System.Data.CommandType.StoredProcedure;
command.CommandText = "msdb.dbo.sp_help_jobactivity";
command.Parameters.AddWithValue("#job_name", jobName);
command.Connection = dbConnection;
using (dbConnection)
{
dbConnection.Open();
using (command)
{
SqlDataReader reader = command.ExecuteReader();
reader.Read();
Object[] values = new Object[reader.FieldCount];
int fieldCount = reader.GetValues(values);
int jobStatus = -1; // inactive
for (int i = 0; i < fieldCount; i++)
{
object item = values[i];
string colName = reader.GetName(i);
if (colName == "run_status")
{
if (values[i] != null)
{
jobStatus = (int)values[i];
break;
}
}
}
reader.Close();
return jobStatus;
}
}
}
This code is what I needed. Taken from MSDN
Thanks #JeroenMostert
SELECT sj.Name,
CASE
WHEN sja.start_execution_date IS NULL THEN 'Not running'
WHEN sja.start_execution_date IS NOT NULL AND sja.stop_execution_date IS NULL THEN 'Running'
WHEN sja.start_execution_date IS NOT NULL AND sja.stop_execution_date IS NOT NULL THEN 'Not running'
END AS 'RunStatus'
FROM msdb.dbo.sysjobs sj
JOIN msdb.dbo.sysjobactivity sja
ON sj.job_id = sja.job_id
WHERE session_id = (
SELECT MAX(session_id) FROM msdb.dbo.sysjobactivity);
You can check it through a stored procedure sp_help_job in the msdb database.
So just run:
Use msdb
go
exec dbo.sp_help_job
it will return all the jobs details where you can find one column named current_execution_status. If it's 1 means it's running. You can get more info from the link sp_help_job
You can provide parameter to the stored procedure as well.
An error is thrown when there is no data in data base while converting a string value into int.
try {
SqlCommand cmdc = new SqlCommand("SELECT SUM(Credited_amount) FROM IMS_Credit_Dir WHERE Credit_comp_id=1 AND Crdt_typ_id=1", con);
string companya_credit_amount = null, comapnyb_credit_amount = null;
con.Open();
SqlDataReader drc = cmdc.ExecuteReader();
if (drc.HasRows)
{
while (drc.Read())
{
companya_credit_amount = drc[0].ToString();
}
drc.Close();
con.Close();
}
SqlCommand cmdcp = new SqlCommand("SELECT SUM(Credited_amount) FROM IMS_Credit_Dir WHERE Credit_comp_id=2 AND Crdt_typ_id=1", con);
con.Open();
SqlDataReader drcp = cmdcp.ExecuteReader();
if (drcp.HasRows)
{
while (drcp.Read())
{
companyb_credit_amount = drcp[0].ToString();
}
drcp.Close();
con.Close();
}
if (!Page.IsPostBack)
{
int companyA = 0,companyB=0;
if (companya_credit_amount != "") { companyA = Convert.ToInt32(credit_amount.ToString()); }
if (companyb_credit_amount != ""){ companyB = Convert.ToInt32(companyb_credit_amount); }
int total = (companyA+companyB);
count_total_lbl.Text = "Rs." + " " + total.ToString();
count_comapnya_lbl.Text = "Rs." + " " + companya_credit_amount.ToString();
count_companyb_lbl.Text ="Rs."+" "+ companyb_credit_amount.ToString();
}
}
catch(Exception ex) { Label2.Text = ex.ToString(); }
If there is value its working fine.but when there is no value in data base there is an error msg.
System.FormatException: Input string was not in a correct format.
Use IsDBNull to check for null values
Create and destroy all your type instances that implement IDisposable in using blocks. This ensures that connections are always released and resources are cleaned up.
Do not use connections across a class. Create them when needed and then dispose of them. Sql Server will handle connection pooling.
Get the native types directly, not the string equivalent! See changes to GetInt32 instead of ToString on the data reader.
You should refactor this to use SqlParameter's and make the retrieval statement generic OR get both SUM values in 1 sql call.
There is an if (!Page.IsPostBack) statement, if none of this code does anything if it is a postback then check at the top of the page and do not execute the sql statements if it is a postback. Otherwise the code is making (possibly) expensive sql calls for no reason.
try
{
int companyA = 0,companyB=0;
using(var con = new SqlConnection("connectionStringHere"))
{
con.Open();
using(SqlCommand cmdc = new SqlCommand("SELECT SUM(Credited_amount) FROM IMS_Credit_Dir WHERE Credit_comp_id=1 AND Crdt_typ_id=1", con))
using(SqlDataReader drc = cmdc.ExecuteReader())
{
if (drc.Read() && !drc.IsDBNull(0))
companyA = drc.GetInt32(0);
}
using(SqlCommand cmdcp = new SqlCommand("SELECT SUM(Credited_amount) FROM IMS_Credit_Dir WHERE Credit_comp_id=2 AND Crdt_typ_id=1", con))
using(SqlDataReader drcp = cmdcp.ExecuteReader())
{
if (drcp.Read() && !drcp.IsDBNull(0))
companyB = drcp.GetIn32(0);
}
}
// if you are not going to do anything with these values if its not a post back move the check to the top of the method
// and then do not execute anything if it is a postback
// ie: // if (Page.IsPostBack) return;
if (!Page.IsPostBack)
{
int total = (companyA+companyB);
count_total_lbl.Text = "Rs." + " " + total.ToString();
count_comapnya_lbl.Text = "Rs." + " " + companyA.ToString();
count_companyb_lbl.Text ="Rs."+" "+ companyB.ToString();
}
}
catch(Exception ex) { Label2.Text = ex.ToString(); }
Try to replace this
SELECT SUM(Credited_amount)
WITH
SELECT ISNULL(SUM(Credited_amount),0)
Also find one confusing code while converting Credited amount values
if (companya_credit_amount != "") { companyA = Convert.ToInt32(credit_amount.ToString()); }
---------^^^^^
if (companyb_credit_amount != ""){ companyB = Convert.ToInt32(companyb_credit_amount); }
I don't know about your business requirement but What i think Instead of using credit_amount value companya_credit_amount should be use to show value for companyA variable right?
You should do 2 things:
string companya_credit_amount = "", comapnyb_credit_amount = "";
Before assigning the value to these string variable you should check for db null as following:
while (drc.Read())
{
companya_credit_amount = (drc[0] != DbNull.Value) ? drc[0].ToString() : "" ;
}
Similarely
while (drcp.Read())
{
companyb_credit_amount = (drcp[0] != DbNull.Value) ? drcp[0].ToString() : "";
}
Try it.
You need to initialize credit_amount to empty and check if db value is null as shown below:
try {
companya_credit_amount = string.Empty;
companyb_credit_amount = string.Empty;
SqlCommand cmdc = new SqlCommand("SELECT SUM(Credited_amount) FROM IMS_Credit_Dir WHERE Credit_comp_id=1 AND Crdt_typ_id=1", con);
string companya_credit_amount = null, comapnyb_credit_amount = null;
con.Open();
SqlDataReader drc = cmd
c.ExecuteReader();
if (drc.HasRows)
{
while (drc.Read())
{
companya_credit_amount = drcp.IsDBNull(0)?string.Empty:Convert.ToString(drcp[0]);
}
drc.Close();
con.Close();
}
SqlCommand cmdcp = new SqlCommand("SELECT SUM(Credited_amount) FROM IMS_Credit_Dir WHERE Credit_comp_id=2 AND Crdt_typ_id=1", con);
con.Open();
SqlDataReader drcp = cmdcp.ExecuteReader();
if (drcp.HasRows)
{
while (drcp.Read())
{
companyb_credit_amount = drcp.IsDBNull(0)?string.Empty:Convert.ToString(drcp[0]);
}
drcp.Close();
con.Close();
}
if (!Page.IsPostBack)
{
int companyA = 0,companyB=0;
if (companya_credit_amount != "") { companyA = Convert.ToInt32(credit_amount.ToString()); }
if (companyb_credit_amount != ""){ companyB = Convert.ToInt32(companyb_credit_amount); }
int total = (companyA+companyB);
count_total_lbl.Text = "Rs." + " " + total.ToString();
count_comapnya_lbl.Text = "Rs." + " " + companya_credit_amount.ToString();
count_companyb_lbl.Text ="Rs."+" "+ companyb_credit_amount.ToString();
}
}
catch(Exception ex) { Label2.Text = ex.ToString(); }
This is my code:
db.Open();
string updateString = "SELECT TOP 1 RTRIM(kol) kol, RTRIM(adres) adres, RTRIM(numwave) numwave FROM sorters WHERE kodprod=#kodprod AND sorter_kod=#sorter AND moved_ok IS NULL ORDER BY CAST(kol as int)";
try
{
SqlCommand command = new SqlCommand(updateString, db);
//command.Parameters.AddWithValue("#numdoc", NumDoc);
command.Parameters.AddWithValue("#kodprod", KodProd.Id);
command.Parameters.AddWithValue("#sorter", SorterKod);
SqlDataReader reader = command.ExecuteReader();
reader.Read();//here error
Kol = reader["kol"].ToString();
Adres = reader["adres"].ToString();
NumWave = reader["numwave"].ToString();
NumDoc = reader["numdoc"].ToString();
reader.Close();
}
catch (Exception ex)
{ }
Why do I get this error when I run my code?:
Invalid attempt to read when no data is present
You can check whether the DataReader is ready to fetch the rows
if(reader.HasRows)
{
//do the coding here
}
I believe the error will in fact occur on the next line, viz when you access the reader via the index [] operator. What you need to do is check the result of reader.Read() before accessing it:
if (reader.Read())
{
Kol = reader["kol"].ToString();
Adres = reader["adres"].ToString();
NumWave = reader["numwave"].ToString();
NumDoc = reader["numdoc"].ToString();
}
Since you are only returning a maximum of one row (TOP 1) there will either be zero or one rows.
you should do a while loop to check reader contain data. You can also use IF if you are sure the query return only one row. If more than one row you should use While. In your case IF also do the job because you are only taking TOP1
string updateString = "SELECT TOP 1 RTRIM(kol) kol, RTRIM(adres) adres,
RTRIM(numwave) numwave FROM sorters WHERE
kodprod=#kodprod AND sorter_kod=#sorter
AND moved_ok IS NULL ORDER BY CAST(kol as int)";
try
{
SqlCommand command = new SqlCommand(updateString, db);
//command.Parameters.AddWithValue("#numdoc", NumDoc);
command.Parameters.AddWithValue("#kodprod", KodProd.Id);
command.Parameters.AddWithValue("#sorter", SorterKod);
SqlDataReader reader = command.ExecuteReader();
while(reader.Read())
{
Kol = reader["kol"].ToString();
Adres = reader["adres"].ToString();
NumWave = reader["numwave"].ToString();
NumDoc = reader["numdoc"].ToString();
}
reader.Close();
}
Use reader.HasRows
string updateString = "SELECT TOP 1 RTRIM(kol) kol, RTRIM(adres) adres, RTRIM(numwave) numwave FROM sorters WHERE kodprod=#kodprod AND sorter_kod=#sorter AND moved_ok IS NULL ORDER BY CAST(kol as int)";
try
{
SqlCommand command = new SqlCommand(updateString, db);
//command.Parameters.AddWithValue("#numdoc", NumDoc);
command.Parameters.AddWithValue("#kodprod", KodProd.Id);
command.Parameters.AddWithValue("#sorter", SorterKod); SqlDataReader
reader = command.ExecuteReader();
if(reader.HasRows)
while(reader.Read())//here error
{
Kol = reader["kol"].ToString();
Adres = reader["adres"].ToString();
NumWave = reader["numwave"].ToString();
NumDoc = reader["numdoc"].ToString();
}
reader.Close();
}
catch{}
EDIT: sorry for the bad formatting, posting code from the Android app is a mess.
EDIT: See Microsoft example here
With the following code I get a less-than-helpful err msg (all I can see of the err msg in the truncated title bar of the exception dialog is, "System.Data.SQLServer...")
string query = "SELECT * FROM EVERYTHING";
SqlCeCommand cmd = new SqlCeCommand(query);
SqlCeConnection conn = new SqlCeConnection(myConnStr);
conn.Open();
cmd.Connection = conn;
SqlCeDataReader myReader = cmd.ExecuteReader(CommandBehavior.CloseConnection); // <-- Blows up bigger than an Augustus Gloop pinata
UPDATE
I added this:
MessageBox.Show(string.Format("query is {0}", query));
...to do a sanity check on just what the query that was failing was, to the end that clumps of hair are now scattered all about my work area. I had this to feed the query:
string vendorId = txtVendor.ToString().Trim();
...instead of this:
string vendorId = txtVendor.Text.ToString().Trim();
...and thus the query was "SELECT BLA FROM BLA WHERE BLA = System.Windows.Forms.Label"
Now I'm at least to a "No data exists for the row/column" err msg.
I'm not sure if CF supports the CommandBehavior.CloseConnection option.
Can you write it this way?
string query = "SELECT * FROM EVERYTHING";
var table = new DataTable();
using (var cmd = new SqlCeCommand(query, new SqlCeConnection(myConnStr)); {
try {
cmd.Connection.Open();
table.Load(cmd.ExecuteReader());
} catch (SqlException err) {
Console.WriteLine(err.Message); // <= Put a Break Point here.
} finally {
cmd.Connection.Close();
}
}
object col1 = null;
string strCol2 = null;
if (0 < table.Rows.Count) {
col1 = table.Rows[0][0];
object obj = table.Rows[0][1];
if ((obj != null) && (obj != DBNull.Value)) {
strCol2 = obj.ToString();
}
}
EDIT: Added DataTable and read 2 items from Row[0].