I'm working on a web form that validates data that the user uploads in the form of an Excel file. The code iterates through each row in the spreadsheet and checks against various rules, one of which is that the reference must be a unique value. I have a stored procedure that takes the userID and referenceNum as parameters:
BEGIN
SET NOCOUNT ON;
DECLARE #Status AS BIT
IF EXISTS (SELECT [TransactionMstID]
FROM [dbo].[tbl_TransactionMst]
WHERE [TransactionRef] = #DocumentNumber
AND [SupplierID] = #SupplierID)
BEGIN
SET #Status = 0
END
ELSE
BEGIN
SET #Status = 1
END
SELECT #Status AS [Status]
END
When I try different scenarios in SQL Server Management Studio (SSMS), I get the desired outputs e.g. a "0" when the reference exists and a "1" when it doesn't.
The problem arises in my C# code, it executes the stored procedure, but in my testing I get the same result irrespective of whether the data exists or not.
Here's the core of the C#:
bool returnValue = true;
if (Docnumber != null)
{
SqlConnection con = new SqlConnection(GlobalSettings.connection);
con.Open();
SqlCommand Cmd = new SqlCommand("p_ValRefNumber", con);
Cmd.CommandType = System.Data.CommandType.StoredProcedure;
Cmd.Parameters.AddWithValue("#DocumentNumber", Docnumber);
Cmd.Parameters.AddWithValue("#SupplierID", SupplierID);
Cmd.ExecuteNonQuery();
SqlDataReader dr = Cmd.ExecuteReader();
while (dr.Read())
{
bool Status = convertor.ConvertToBool(dr["Status"]);
string test = dr["Status"].ToString();
int testint = convertor.ConvertToInt(dr["Status"].ToString());
if (Status == false)
{
//throw new System.Exception(CEObj.GetErrorDesc(101));
returnValue = false;
}
}
dr.Close();
con.Close();
}
return returnValue;
}
No matter what the value of docnumber is in testing, it always shows as True. I've added a breakpoint so that I can check each time and then test in SSMS and I get conflicting results.
Is my logic wrong? Does Visual Studio treat the values differently? How is the result not consistent when converting it to a string - at the very least? It always seems to read a value of "1" in VS but varies in SSMS
Edit: here's my converter method's code:
public static bool ConvertToBool(object value)
{
bool result = false;
if (value != null)
{
bool.TryParse(value.ToString(), out result);
}
return result;
}
bool.TryParse isn't doing what the convertor (sic) code thinks it does.
bool.TryParse returns true if the value parameter equals bool.TrueString, which is the literal string "True". It returns false for any other value, which means it returns false for both 0 and 1.
Also, T-SQL bit values are numbers. The converter code isn't really necessary - just convert the return value to an Int32 and do a comparison.
using (var con = new SqlConnection(GlobalSettings.connection))
{
con.Open();
using (var cmd = new SqlCommand() { Connection = con, CommandType = CommandType.StoredProcedure, CommandText = "p_ValRefNumber" })
{
/* Assuming both parameters are integers.
Change SqlDbType if necessary. */
cmd.Parameters.Add(new SqlParameter() { ParameterName = "#DocumentNumber", SqlDbType = SqlDbType.Int, Value = Docnumber });
cmd.Parameters.Add(new SqlParameter() { ParameterName = "#SupplierID", SqlDbType = SqlDbType.Int, Value = SupplierID });
using (var reader = cmd.ExecuteReader(CommandBehavior.CloseConnection))
{
return dr.Read() && (Convert.ToInt32(dr["Status"]) == 1)
}
}
}
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.
SqlConnection conn = getConnection();
SqlCommand cmd = new SqlCommand();
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandText = "SP_PSLA_SEARCH"; //The stored procedure gets added
cmd.CommandTimeout = 0;
cmd.Connection = conn;
// Start adding the parameters of the stored procedure
cmd.Parameters.AddWithValue("#usrnm", thisUser.Username);
int constit = 0;
if (thisUser.Constituencies.Count > 0)
{
foreach (KeyValuePair<int, string> kp in thisUser.Constituencies)
{
if (kp.Value == ddlConstituency.SelectedValue.ToString())
{
constit = kp.Key;
break;
}
}
}
cmd.Parameters.AddWithValue("#cnstncy", constit);
string pdval = null;
int valtype = 0;
if (rbsearchradios.SelectedIndex == 0)
{
try
{
pdval = searchVal;
cmd.Parameters.AddWithValue("#Search", DBNull.Value);
cmd.Parameters.AddWithValue("#pd", int.Parse(pdval));
cmd.Parameters.AddWithValue("#type", valtype);
}
catch
{
System.Web.UI.ScriptManager.RegisterStartupScript(this, this.GetType(), "stop", "alert('Invalid PD Number Supplied! Please Provide A Valid Submission.');", true);
return;
}
}
else
{
valtype = 1;
cmd.Parameters.AddWithValue("#Search", searchVal);
cmd.Parameters.AddWithValue("#pd", DBNull.Value);
cmd.Parameters.AddWithValue("#type", valtype);
}
cmd.Parameters.AddWithValue("#app", 1);
conn.Open();
// Creates Dataadapter for execution
SqlDataAdapter dp2 = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
dp2.Fill(ds, "name");
I am trying to the arguments of the stored procedure and the having this stored procedure execute and get this results into a dataset but I get nothing.. Literally. There are no exceptions, just no result from the stored procedure.
This is the stored procedure:
DECLARE #return_value int
EXEC #return_value = [dbo].[SP_PSLA_SEARCH]
#usrnm = N'tstone',
#cnstncy = 55,
#Search = N'primary',
#pd = NULL,
#type = 1,
#app = 1
SELECT 'Return Value' = #return_value
GO
To troubleshoot:
Make sure what values has each parameter and execute the same query directly against database in Sql Server Management Studio.
Check if you properly use the result from the dataset (it's not clear from the code)
In general, you can also try to simplify and make your code more clear:
the block with return and if (rbsearchradios.SelectedIndex == 0) can be moved at the beginning, it makes no sense to create SqlCommand and then break
if SP returns only single value, you can use the ExecuteScalar() method, which is faster and straightforward.
I am trying to determine if a specific value exists in a Oracle database table.
I used a query with "select count(*)", "select count(1)" and select count(<col_name>)" but keep getting the wrong result. When I use SQL Developer and run the query I get zero for the count. However, in the DAL, I get 1. I am guessing it is returning the number of row rather than the count itself. I tried both executeScalar() and ExecuteReader().
public override bool zipExists(string sZipCode)
{
OracleConnection conn = new OracleConnection(this.OraDataConnectionString);
OracleCommand oraCmd = new OracleCommand();
decimal iNumEntries = 0;
string sQuery = "select count(ZIPCODEID) as ZipCount from ZIPCODE where ZIPCODE = :ZipCode";
SetOraCommandType(oraCmd, CommandType.Text, sQuery);
conn.Open();
oraCmd.Connection = conn;
oraCmd.BindByName = true;
AddParamToOraCmd(oraCmd, "ZipCode", OracleDbType.Varchar2, 11, ParameterDirection.Input, sZipCode);
using (OracleConnection cn = new OracleConnection(this.OraDataConnectionString))
{
oraCmd.Connection = cn;
cn.Open();
iNumEntries = (decimal)oraCmd.ExecuteScalar();
}
return iNumEntries > 0;
also tried:
OracleDataReader sqlReader = oraCmd.ExecuteReader();
try
{
if (sqlReader.Read())
{
if (sqlReader["ZipCount"] != DBNull.Value)
iNumEntries = Convert.ToInt16(sqlReader["ZipCount"]);
}
}
}
return iNumEntries > 0;
I try you code on my table but pointing to some column and giving a select count(EN_Qty) as ZipCount from PSLAT.FSDEV.dbo.PS_EN_GEN_INTFC_BI where EN_Qty = '2600' works on my end so where in the code exactly are you experiencing an issue..? fyi I replaced my table with your query and assigned a value to the where clause.. so you query looks right.. however I would do an order by query to see if you perhaps are missing a zipcode..also oraCmd.ExecuteScalar() returns only 1 row so make sure you are not returning more than one row..oracle is funny like that
change your code to the following
object bExists = oraCmd.ExecuteScalar();
var bexists = bExists != DBNull.Value && result != null;
or change your code to check for row.count > 0 if true then you know the zipcode was found. Remember when making changes to Sql scripts or stored procedures in Oracle, you need to Compile the changes otherwise the changes will be visible to you when looking at the code but not to the caller trying to execute the stored proc.
I am using the following SQL query and the ExecuteScalar() method to fetch data from an Oracle database:
sql = "select username from usermst where userid=2"
string getusername = command.ExecuteScalar();
It is showing me this error message:
System.NullReferenceException: Object reference not set to an instance of an object
This error occurs when there is no row in the database table for userid=2.
How should I handle this situation?
According to MSDN documentation for DbCommand.ExecuteScalar:
If the first column of the first row in the result set is not found, a
null reference (Nothing in Visual Basic) is returned. If the value in
the database is null, the query returns DBNull.Value.
Consider the following snippet:
using (var conn = new OracleConnection(...)) {
conn.Open();
var command = conn.CreateCommand();
command.CommandText = "select username from usermst where userid=2";
string getusername = (string)command.ExecuteScalar();
}
At run-time (tested under ODP.NET but should be the same under any ADO.NET provider), it behaves like this:
If the row does not exist, the result of command.ExecuteScalar() is null, which is then casted to a null string and assigned to getusername.
If the row exists, but has NULL in username (is this even possible in your DB?), the result of command.ExecuteScalar() is DBNull.Value, resulting in an InvalidCastException.
In any case, the NullReferenceException should not be possible, so your problem probably lies elsewhere.
First you should ensure that your command object is not null. Then you should set the CommandText property of the command to your sql query. Finally you should store the return value in an object variable and check if it is null before using it:
command = new OracleCommand(connection)
command.CommandText = sql
object userNameObj = command.ExecuteScalar()
if (userNameObj != null)
string getUserName = userNameObj.ToString()
...
I'm not sure about the VB syntax but you get the idea.
I just used this:
int? ReadTerminalID()
{
int? terminalID = null;
using (FbConnection conn = connManager.CreateFbConnection())
{
conn.Open();
FbCommand fbCommand = conn.CreateCommand();
fbCommand.CommandText = "SPSYNCGETIDTERMINAL";
fbCommand.CommandType = CommandType.StoredProcedure;
object result = fbCommand.ExecuteScalar(); // ExecuteScalar fails on null
if (result.GetType() != typeof(DBNull))
{
terminalID = (int?)result;
}
}
return terminalID;
}
The following line:
string getusername = command.ExecuteScalar();
... will try to implicitly convert the result to string, like below:
string getusername = (string)command.ExecuteScalar();
The regular casting operator will fail if the object is null.
Try using the as-operator, like this:
string getusername = command.ExecuteScalar() as string;
sql = "select username from usermst where userid=2"
var _getusername = command.ExecuteScalar();
if(_getusername != DBNull.Value)
{
getusername = _getusername.ToString();
}
Check out the example below:
using System;
using System.Data;
using System.Data.SqlClient;
class ExecuteScalar
{
public static void Main()
{
SqlConnection mySqlConnection =new SqlConnection("server=(local)\\SQLEXPRESS;database=MyDatabase;Integrated Security=SSPI;");
SqlCommand mySqlCommand = mySqlConnection.CreateCommand();
mySqlCommand.CommandText ="SELECT COUNT(*) FROM Employee";
mySqlConnection.Open();
int returnValue = (int) mySqlCommand.ExecuteScalar();
Console.WriteLine("mySqlCommand.ExecuteScalar() = " + returnValue);
mySqlConnection.Close();
}
}
from this here
SQL NULL value
equivalent in C# is DBNull.Value
if a NULLABLE column has no value, this is what is returned
comparison in SQL: IF ( value IS NULL )
comparison in C#: if (obj == DBNull.Value)
visually represented in C# Quick-Watch as {}
Best practice when reading from a data reader:
var reader = cmd.ExecuteReader();
...
var result = (reader[i] == DBNull.Value ? "" : reader[i].ToString());
In my experience, there are some cases the returned value can be missing and thus execution fails by returning null. An example would be
select MAX(ID) from <table name> where <impossible condition>
The above script cannot find anything to find a MAX in. So it fails. In these such cases we must compare the old fashion way (compare with C# null)
var obj = cmd.ExecuteScalar();
var result = (obj == null ? -1 : Convert.ToInt32(obj));
If you either want the string or an empty string in case something is null, without anything can break:
using (var cmd = new OdbcCommand(cmdText, connection))
{
var result = string.Empty;
var scalar = cmd.ExecuteScalar();
if (scalar != DBNull.Value) // Case where the DB value is null
{
result = Convert.ToString(scalar); // Case where the query doesn't return any rows.
// Note: Convert.ToString() returns an empty string if the object is null.
// It doesn't break, like scalar.ToString() would have.
}
return result;
}
Always have a check before reading row.
if (SqlCommand.ExecuteScalar() == null)
{
}
This is the easiest way to do this...
sql = "select username from usermst where userid=2"
object getusername = command.ExecuteScalar();
if (getusername!=null)
{
//do whatever with the value here
//use getusername.toString() to get the value from the query
}
In your case either the record doesn't exist with the userid=2 or it may contain a null value in first column, because if no value is found for the query result used in SQL command, ExecuteScalar() returns null.
Alternatively, you can use DataTable to check if there's any row:
SqlCommand cmd = new SqlCommand("select username from usermst where userid=2", conn);
SqlDataAdapter adp = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
adp.Fill(dt);
string getusername = "";
// assuming userid is unique
if (dt.Rows.Count > 0)
getusername = dt.Rows[0]["username"].ToString();
private static string GetUserNameById(string sId, string connStr)
{
System.Data.SqlClient.SqlConnection conn = new System.Data.SqlClient.SqlConnection(connStr);
System.Data.SqlClient.SqlCommand command;
try
{
// To be Assigned with Return value from DB
object getusername;
command = new System.Data.SqlClient.SqlCommand();
command.CommandText = "Select userName from [User] where userid = #userid";
command.Parameters.AddWithValue("#userid", sId);
command.CommandType = CommandType.Text;
conn.Open();
command.Connection = conn;
//Execute
getusername = command.ExecuteScalar();
//check for null due to non existent value in db and return default empty string
string UserName = getusername == null ? string.Empty : getusername.ToString();
return UserName;
}
catch (Exception ex)
{
throw new Exception("Could not get username", ex);
}
finally
{
conn.Close();
}
}
Slight conjecture: if you check the stack for the exception, it is being thrown then the ADO.NET provider for Oracle is reading the underlying rowset to get the first value.
If there is no row, then there is no value to find.
To handle this case execute for a reader and handle Next() returning false for the case of no match.
I Use it Like This with Microsoft Application Block DLL (Its a help library for DAL operations)
public string getCopay(string PatientID)
{
string sqlStr = "select ISNULL(Copay,'') Copay from Test where patient_id=" + PatientID ;
string strCopay = (string)SqlHelper.ExecuteScalar(CommonCS.ConnectionString, CommandType.Text, sqlStr);
if (String.IsNullOrEmpty(strCopay))
return "";
else
return strCopay ;
}
I have seen in VS2010
string getusername = command.ExecuteScalar();
gives compilation error,
Cannot implicitly convert type object to string.
So you need to write
string getusername = command.ExecuteScalar().ToString();
when there is no record found in database it gives error
Object reference not set to an instance of an object
and when I comment '.ToString()', it is not give any error. So I can say ExecuteScalar not throw an exception. I think anserwer given by #Rune Grimstad is right.
I had this issue when the user connecting to the database had CONNECT permissions, but no permissions to read from the database. In my case, I could not even do something like this:
object userNameObj = command.ExecuteScalar()
Putting this in a try/catch (which you should probably be doing anyway) was the only way I could see to handle the insufficient permission issue.
object objUserName;
objUserName = command.ExecuteScalar();
if (objUserName == null) //if record not found ExecuteScalar returns null
{
return "";
}
else
{
if (objUserName == DBNull.Value) //if record found but value in record field is null
{
return "";
}
else
{
string getusername = objUserName.ToString();
return getusername;
}
}
/* Select some int which does not exist */
int x = ((int)(SQL_Cmd.ExecuteScalar() ?? 0));
I used this in my vb code for the return value of a function:
If obj <> Nothing Then
Return obj.ToString()
Else
Return ""
End If
Try this code, it appears to solve your problem.
Dim MaxID As Integer = Convert.ToInt32(IIf(IsDBNull(cmd.ExecuteScalar()), 1, cmd.ExecuteScalar()))
I'm using Oracle.
If your sql returns numeric value, which is int, you need to use Convert.ToInt32(object). Here is the example below:
public int GetUsersCount(int userId)
{
using (var conn = new OracleConnection(...)){
conn.Open();
using(var command = conn.CreateCommand()){
command.CommandText = "select count(*) from users where userid = :userId";
command.AddParameter(":userId", userId);
var rowCount = command.ExecuteScalar();
return rowCount == null ? 0 : Convert.ToInt32(rowCount);
}
}
}
Try this
sql = "select username from usermst where userid=2"
string getusername = Convert.ToString(command.ExecuteScalar());