Invalid attempt to read when no data is present.

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Hey Friends... I'm getting this error in my code.. that my sqldatareader not reading any row from database.. though i have inserted many data in my table.

here is the Code:

C#

public partial class Welcome : System.Web.UI.Page
{

    public string username; 

    public string fname;
    public string lname;


    protected void Page_Load(object sender, EventArgs e)
    {
        bindTable2();
    }

    protected void bindTable2()
    {

        string sqlSel = "select * from Table2 where username ='" + username + "' ";

        SqlConnection con = new SqlConnection();
        con.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["ApplicationServices"].ConnectionString;
        con.Open();

        SqlCommand cmd = new SqlCommand(sqlSel, con);
        SqlDataReader sdr = cmd.ExecuteReader();


        sdr.Read();
            

        username = sdr["username"].ToString();

                fname = sdr["fname"].ToString();

                ........... etc
                sdr.close();
          
     }
        
}

And if i'm using :

C#

if (sdr.HasRows)
        {
            while (sdr.Read())
            {

                //All Data here
            }
            sdr.Close();
        }
        else
        {
           Response.Write("I didn't find any relevant data");
          
        }
     }

Then it automatically taking my code to else statement. It's not reading any data from Table2.
don't know why.... Please help me out in it.

Posted 12-Aug-13 9:44am

sh4kti

Updated 12-Aug-13 18:13pm

Thanks7872

v4

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Comments

[no name] 12-Aug-13 15:52pm

Probably because your query is not returning anything.

sh4kti 12-Aug-13 15:57pm

that's what i want to know why ??
the record is in Table2... i think i'm using the right query..
if u have any other then do tell me plz.

fyulaba 12-Aug-13 16:02pm

Have you set a breakpoint on setting the sqlSel string and used the string as a query in SQL manager to check it should be returning rows?

sh4kti 12-Aug-13 16:10pm

If i'm using ::

string sqlSel = "select top 1 * from Table2 order by Id desc";

then it displaying the last entered data...
by my this query is not running when selecting from username.

idenizeni 12-Aug-13 16:26pm

Where is the code where you set the username variable? The issue is probably because you never set the username variable so the query is looking for the record with a blank username and I am guessing there is no SQL record with a blank username. If you do as fyulaba suggests and set a breakpoint at the line after you set the sqlSel value you can see the actual SQL query going to the SQL server.

sh4kti 12-Aug-13 16:39pm

Ok got the point...do tell me....if i have a username value already stored in the database...and i just want my Query to select the username from the database...display it's other related data... then.. what Query should i write ??

if i'm using this code :

string sqlSel = "select * from Table2 where username ='" + Request["username"] + "' ";

then too same problem exist.

In aspx.cs im using ::

User name: <%=username%>
First Name: <%=fname%> ....etc

idenizeni 12-Aug-13 16:49pm

As a test try replacing your SQL query string...

string sqlSel = "select * from Table2 where username ='" + username + "' ";

with this SQL query string (be sure to replace the [username] text with actual username)...

string sqlSel = "select * from Table2 where username ='[username]' ";

Replace the [username] text with literal text of a username you know exists. Run your code, if you get a record the issue is with how you are setting the username variable.

FYI; if you click reply to this comment I will be notified, if you just add a new comment I will not be notified.

sh4kti 12-Aug-13 17:21pm

Yeah.. it's displaying the record when i'm writing the code as string sqlSel = "select * from Table2 where username ='abc' "; the record is displaying. Do tell me.. please why now i'm getting wrong. ?

idenizeni 12-Aug-13 17:36pm

You are not setting the username variable before your query is called. How do you set username variable in your program? I don't see the code for that. You need to set the username before you call your query. From your code it looks like the page is loaded and the query called but the username variable is never set. Are you only calling the bindTable2() method from the page load or are there other methods that call it?

sh4kti 12-Aug-13 17:38pm

Then can you please help me out to set the username variable ??
i'm new so i don't know what i'm missing.

idenizeni 12-Aug-13 17:43pm

Well you could do this...

username = "abc";
string sqlSel = "select * from Table2 where username ='" + username + "' ";

...but then you would always return the same user. I am guessing you what to show different users based a users selection. It really depends how the intent of your program.

sh4kti 12-Aug-13 17:47pm

First of all thanks for all your help..
Yeah you are right.. i want for different users.. the user who login with his user id can get his information displayed on the page. it only possible if the query runs with username logined.

idenizeni 12-Aug-13 17:56pm

Glad to help. You need to get the current user's name and set it to the username variable before you set the sqlSel string. This depends on how you have setup users and security in you site.

If you are using impersonation you could do this to get the user name (note it will include the domain prefix)...

username = HttpContext.Current.User.Identity.Name;

sh4kti 12-Aug-13 17:59pm

Thanks a lot .. :)
really helpful... :)
let me see it :) will post if got any further Query.

Thank you once again :)

sh4kti 12-Aug-13 17:41pm

like any simple example you can give. it will be really helpful.

3 solutions

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fyulaba · Answer 1 · 2013-08-12T09:52:00

Solution 1

Where are you initialising te username variable? if its blank your sql query might not return any rows.

Posted 12-Aug-13 9:52am

fyulaba

Comments

sh4kti 12-Aug-13 15:58pm

username variable in in table1 and in table2
i want to fetch the record from username which i have inserted into table2.

fyulaba 12-Aug-13 16:07pm

First line of bindTable2 you are reading from the username variable but it may not have been set yet.

string sqlSel = "select * from Table2 where username ='" + username + "' ";

sh4kti 12-Aug-13 16:15pm

Yeah that's where i too stuck... but don't understand what to do as i have to display the data with username.

if i use ::

string sqlSel = "select top 1 * from Table2 order by Id desc";

then it displaying the last entered data...

but i need the query to fetch the data by username.

Richard C Bishop 12-Aug-13 16:52pm

Use the "Have a Question of Comment?" widget to ask questions. You posted a question as a solution to this question. Do you see the paradox you created?

sh4kti 12-Aug-13 17:22pm

am sorry... from next time i will use the reply option.

Richard C Bishop 12-Aug-13 17:23pm

It's all good, just a friendly reminder.

sh4kti 12-Aug-13 17:24pm

Thanks :) as i'm new here.. so still to learn :)

silvercr0w · Answer 2 · 2013-08-12T10:21:00

Solution 3

Maybe the query isn't sending data back because the variable username has no value yet.

Check in your DB manager if that query returns the desired data.

Posted 12-Aug-13 10:21am

silvercr0w

Updated 12-Aug-13 12:02pm

v2

Comments

sh4kti 12-Aug-13 16:31pm

I have made a login and register form... in which i had taken two tables table1 and table 2.
i'm using username as a foreign key in table2 ..
it's a 2 step process or filling the Registration form.
the Registration page is working fine.. and username automatically get filled in table2..it working correctly in both the table.

now i want to display the profile of user.. where i'm using this Query to get the data to be displayed.

rest of mine code is working fine.. but here only i get stuck.

am sorry i didn't understand what you are trying to say.. " assign a value to string variable username ??? ""
in aspz.cs
i'm using like this

Username : <%=username %>
.....
NOW TELL HELP ME..

Richard C Bishop 12-Aug-13 16:52pm

Use the "Have a Question of Comment?" widget to ask questions. You posted a question as a solution to this question. Do you see the paradox you created?

silvercr0w 12-Aug-13 18:03pm

I'm sorry, thanks for the advice richcb. I will edit my previous answer.

Richard C Bishop 13-Aug-13 10:07am

It's all good, just a friendly reminder.

blachsmith · Answer 3 · 2013-08-12T16:46:00

Solution 4

string sqlSel = "select * from Table2 where username ='" + username + "' "; have you make a breakpoint to see the username's value in this code ?

I think username hasn't got a value everytime the page is loaded

Posted 12-Aug-13 16:46pm

blachsmith

Updated 12-Aug-13 16:47pm

v2