database query and datagridview

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Hi
I want to know total number of students registered in a particular course whose ID is in "DGVC.Rows[r].Cells[c]".

I've tried this code,it should show 1 in messagebox,as one student is registered to the course, but it gives -1. what shoud i do?

C#

Connection cc = new Connection();
cc.con.Open();

SqlCommand cmdC = new SqlCommand("Select Count(*) from UCK_Scheduler..COURSE_REGISTRATION inner join UCK_Scheduler..STUDENT on COURSE_REGISTRATION.StudentID=STUDENT.StudentID where CourseID='" + DGVC.Rows[r].Cells[c].Value.ToString() + "' ", cc.con);

int cn = cmdC.ExecuteNonQuery();
MessageBox.Show(cn.ToString());
cc.con.Close();

Posted 9-Oct-13 19:38pm

suleman115

Updated 9-Oct-13 21:16pm

Ryan Zahra

v2

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5 solutions

Solution 2

If CourseID is Integer field, then you need to modify the query like below excluding extra single quote.

C#

SqlCommand cmdC = new SqlCommand("Select Count(*) from UCK_Scheduler..COURSE_REGISTRATION inner join UCK_Scheduler..STUDENT on COURSE_REGISTRATION.StudentID=STUDENT.StudentID where CourseID=" + DGVC.Rows[r].Cells[c].Value.ToString() + "", cc.con);

Please debug you code and see what is the value of the query at runtime. Then take the query to SQL Management Studio and run it. You can see the errors, if any.

Posted 9-Oct-13 21:32pm

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ)

Solution 5

Yes i should have used ExecuteScalar() instead of ExecuteNonQuery,thank you all.

Posted 10-Oct-13 4:18am

suleman115

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Ryan Zahra · Accepted Answer · 2013-10-09T21:20:00

You're using the ExecuteNonQuery method to select. That is wrong because ExecuteNonQuery is used to insert/update/delete records. In your case, since you're retrieving a single column, you can use ExecuteScalar which retrieves the item found in the first row from the first column.

Further reading here:
ExecuteNonQuery
ExecuteScalar
Comparision between ExecuteNonQuery and ExecuteScalar

seyed mahmud shahrokni · Accepted Answer · 2013-10-09T22:33:00

Solution 3

you should use ExecuteScalar() not ExecuteNonQuery()

we use EXcuteReader() and ExcuteScalar() for fetch operations and
ExcuteNonQuery() for update and delete operations,

Posted 9-Oct-13 22:33pm

seyed mahmud shahrokni

Chintan Desai1988 · Accepted Answer · 2013-10-10T02:07:00

In sql statement, ExecuteNonQuery is normally used for performing DML operation which allow you to insert, update and delete statement where for latching data from database you have to use ExecuteReader or ExecuteScalar because by using ExecuteReader it's normally used to read data from database tables which return number of record or rows and by using ExecuteScalar it's return the scalar value returns as a one value of first row and first column from database table.

I hope you understand well......!!!