hi name is not displaying in name?

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1.00/5 (1 vote)

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hi here is my code.

protected void Search_Click(object sender, ImageClickEventArgs e)
   {


       SearchFacultyPL stPL = new SearchFacultyPL();
       stPL.RoomNo = ddlSemister.SelectedValue;
       stPL.ExamDate = ddlDate.SelectedValue;
       stPL.eSession = ddlSession.SelectedValue;


       //stPL.aNo = ddlAno.SelectedValue;


       SearchFacultyBLL stBLL = new SearchFacultyBLL();
       DataTable dt = new DataTable();
       dt = stBLL.SearchRoomDetails(stPL);

       if (dt.Rows.Count > 0)
       {
          grdTimeTable.DataSource = dt;
           grdTimeTable.DataBind();
       }


       if (connection.State!= ConnectionState.Open)
       {
           connection.Close();
       }
       connection.Open();

       SqlCommand cmd5 = new SqlCommand();
       SqlDataReader dr5;
       cmd5.Connection = connection;
       cmd5.CommandText = "select facultycode from fAllotmentTab where RoomNo='" + ddlSemister.SelectedValue + "' and ExamDate='" + ddlDate.SelectedValue + "' and eSession='" + ddlSession.SelectedValue + "'";
       dr5 = cmd5.ExecuteReader();



       //if (dr5.Read())
       //{
       //    labelmsg.Text = "Alloted Faculty : " + dr5.GetValue(0).ToString();
       //}
       //else { labelmsg.Text = "Alloted Faculty : "; }
       labelmsg.Text = (dr5.Read()) ? "Alloted Faculty : " + dr5.GetValue(0).ToString() : "Alloted Faculty : ";

when i search and i want to display that faculty name to that label.but its not displaying can any one suggest me?

Posted 16-Mar-12 7:10am

ythisbug

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Sergey Alexandrovich Kryukov · Accepted Answer · 2012-03-16T07:37:00

Solution 1

First of all, you need to run this code under debugger and see what is returned in data reader. Why do you assume there is only one record? I cannot see the returned data set because I don't have you database and don't even know its schema. For you, this is easy to pin-point.

What's more important, you do a big mistake in your query. You compose a query using repeated string concatenation. This is already bad, because strings are immutable. You could use string.Format to solve this problem, but even that would be not good enough in your case. The problem is: you are composing the query based on the UI input. You should never ever do it because this is too dangerous from the security standpoint. It is too easy to input not just data (room number or data), but also any fragment of SQL code. This is called SQL injection and is a very well-known exploit. Please see:
http://en.wikipedia.org/wiki/SQL_injection[^].

Also, the string data is untyped, and the performance can be a problem. Look at the article referenced above and read about the importance of parametrized statements. With ADO.NET, you should always use parametrized commands:
http://msdn.microsoft.com/en-us/library/yy6y35y8.aspx[^].

[EDIT]

You cannot use the data reader this way. You should do something like:

C#

if (dr5.HasRows) {
   dr5.Read();
   var someValue = dr5["myColumnName"];
   if (!DBNull.Value.Equals(someValue) {
       string someStringValue someValue as string;
       if (!string.IsNullOrEmpty(someStringValue) ...
   } //if
} //if

But why do you think there is only one row in the data set? Usually the data reader is used to read to the very end.

—SA

Posted 16-Mar-12 7:37am

Sergey Alexandrovich Kryukov

Updated 23-Mar-15 10:27am

v5

Comments

ythisbug 16-Mar-12 13:42pm

hi lablemsg is coming null.

Sergey Alexandrovich Kryukov 16-Mar-12 14:05pm

Sorry, there is no such name in your code.
--SA

Sergey Alexandrovich Kryukov 16-Mar-12 14:06pm

Oh, I see. You cannot mix up data reader with string...
--SA

ythisbug 16-Mar-12 13:43pm

hi can u suggest me more about tat code.where is the mistake.tom i have to submit my project.

Sergey Alexandrovich Kryukov 16-Mar-12 14:04pm

Please read about parametrized command and how the parameters are substituted.
--SA

Sergey Alexandrovich Kryukov 16-Mar-12 14:15pm

See also the updated answer, after [EDIT]
--SA

ythisbug 17-Mar-12 1:02am

if (connection.State!= ConnectionState.Open)
{
connection.Close();
}
connection.Open();

SqlCommand cmd5 = new SqlCommand();
SqlDataReader dr5;
cmd5.Connection = connection;
cmd5.CommandText = "select facultycode from fAllotmentTab where RoomNo='" + ddlSemister.SelectedValue + "' and ExamDate='" + ddlDate.SelectedValue + "' and eSession='" + ddlSession.SelectedValue + "'";
dr5 = cmd5.ExecuteReader();

//if (dr5.Read())
//{
// labelmsg.Text = "Alloted Faculty : " + dr5.GetValue(0).ToString();
//}
//else { labelmsg.Text = "Alloted Faculty : "; }
labelmsg.Text = (dr5.Read()) ? "Alloted Faculty : " + dr5.GetValue(0).ToString() : "Alloted Faculty : ";

hi i want to modify in this code..acually in my another laptop i gave same coding.but its working and in another lap same value s not coming..code everythin i checkd

Sergey Alexandrovich Kryukov 18-Mar-12 15:11pm

OK, so what's the problem? I explained how to do that, did I not?
--SA

Afzaal Ahmad Zeeshan 23-Mar-15 16:27pm

I will vote this answer a 4, because you did mention strings are immutable. But you forgot to mention using StringBuilder, which is a mutable object and provides better performance while updating the strings or using concatenation, or updating values etc. I get your point about memory consumption while mentioning immutability of string objects, that was a great point. But mentioning StringBuilder would have made it better. :) Plus, I fixed a typo.

Richard Deeming 23-Mar-15 16:38pm

Did you notice that this question and answer are three years old?!

Sergey Alexandrovich Kryukov 23-Mar-15 16:45pm

Why some are so concerned with the dates of the posts? As if the issues had expiration time. Consider I made a mistake in some answer. Will any time period fix it? No, so any improvements should be welcome regardless the dates.
—SA

Richard Deeming 23-Mar-15 16:54pm

The OP is unlikely to still be searching for a solution to their question after three years. Unless there is a significant mistake in the existing solution, or important new information about the OP's problem, I don't see any benefit to resurrecting the question.

According to the revision history, the only change was to add the final two sentences ("But why do you think ..."). Hardly sufficient grounds for dragging a three year old question back to the top of the list.

Without an implicit expiration, QA reads like an episode of "Columbo" - every few years, someone comes back to the same conversation with "just one more thing". Pretty soon, the old, solved questions will drown out the new, unsolved questions.

Sergey Alexandrovich Kryukov 23-Mar-15 17:01pm

I think people should be free to comment on any posts at all. How invented the 3-years threshold? Why not 2 or 5? How would decide on that? It just makes no sense. Does it really distract you from fresh posts, or something else? All our arguments would cost more that the real danger of anything...

Just look at our questions and answers: the number of fake questions, non-questions and fake answers already overwhelm the number of those "old" questions put on top. Is there anything to worry about?

—SA

Richard Deeming 23-Mar-15 17:11pm

Commenting is fine - it doesn't drag the post back to the top of the list. Adding a new solution, or editing an existing solution, brings the question back to the top of the list, pushing newer questions off the bottom of the page.

I never said there was a three year threshold - it's just that this question was asked, and answered, three years ago. Personally, I think that any answered question with no activity in the last six months should probably be left alone unless you have some exceptionally good information to add. Other members may disagree, but most do seem to support some sort of implicit expiration on questions.

Quite often, the people resurrecting old solved questions are new members seeking to increase their "score". Should we just ignore them and let them get on with it?

If not, how can we reprimand them for doing something that the "big hitters" are allowed to do?

Sergey Alexandrovich Kryukov 23-Mar-15 17:18pm

I would ignore them, by one simple reason: there are priorities. Many answers and questions are fake, abusive, and we don't eliminate them efficiently. I used to report massive fake answers, fake by their content, not dates; and people don't actively reply by reporting on the abuser's accounts, but I think this is way more harmful, close to spam or plagiarizing, deserve elimination of the members. The author of reasonable answers cannot be blamed on the base of data, there is no a formal reason; and there are too many unreasonable ones...
And also, there is good number of pretty much fake articles...
—SA

Sergey Alexandrovich Kryukov 23-Mar-15 16:43pm

Thank you, Afzaal.
I agree that mention of StringBuilder is important, but why in this context? Remember that using even the mutable string would not resolve the problems, because it would not address SQL injection. The statement of performance problem related to immutable strings would be enough. It's in some other context the solution would be using StringBuilder. Mentioning all aspects may lead to never-ending answer to a single question. However, there is certain point in this; it's just the matter of the volume of the answer and the point where to stop.
—SA

Afzaal Ahmad Zeeshan 23-Mar-15 16:51pm

Oh, that makes sense. I will update my vote, 5ed.