Some time it shows mail id, some time not

Question

1.00/5 (1 vote)

See more:

I have displayed UserMail related to user Id . But some time it shows value and some time it shows balnk. I have used session to fatch Email.

As i am beginner can anyone help me on this or give me any suggestions

What I have tried:

private void Score_Page()
  {

          string id1 = Convert.ToString(Session["UserEmail"]);
          int id = Convert.ToInt32(Session["UserID"]);
          string connection = ConfigurationManager.AppSettings["connection"].ToString();
          SqlConnection con = new SqlConnection(connection);
          con.Open();
          SqlCommand com = new SqlCommand("SELECT  UserEmail ='" + id1 + "',QId,AnswerId,CASE WHEN AnswerResult = 0 THEN 'Incorrect' ELSE CASE WHEN AnswerResult = 1 THEN 'Correct' ELSE 'you have null value' END END FROM t_AnswerSheet WHERE UserId='" + id + "'", con);
          SqlDataAdapter sda = new SqlDataAdapter(com);
          DataTable dt = new DataTable();
          sda.Fill(dt);
          con.Close();
          GridView1.DataSource = dt;
          GridView1.DataBind();
   }

Posted 28-Jun-17 1:31am

Member 11644373

Updated 28-Jun-17 3:16am

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Afzaal Ahmad Zeeshan · Accepted Answer · 2017-06-28T03:16:00

There are several reasons why it would be blank, first thing to make sure of is, the session variable, always check its value before doing anything.

C#

if(Session["UserEmail"] != null) {
   string id1 = Convert.ToString(Session["UserEmail"]);
   // Continue
} else {
   // Do not load anything, value is empty.
}

ASP.NET has policies for sessions, plus browser also comes into action. Thus you need to check whether session has this value, or not. Further down the stream, you should also check if the the "id" is valid in the context or not, such as, why a condition in SELECT clause when it can come in the WHERE clause? These things would count a lot, and if things go right only then show that DataTable otherwise show a Label saying that the email was not found for this user; show the id as well for debugging purposes.

Also, never concatenate SQL queries, they are exposed to SQL Injection[^], and no one likes injections. You code should be like,

C#

// I removed the = '' from UserEmail in SELECT, add if needed; check CASE blocks too.
SqlCommand com = new SqlCommand(
"SELECT  UserEmail, QId, AnswerId, 
    CASE WHEN AnswerResult = 0 THEN 
       'Incorrect' 
    ELSE 
       CASE WHEN AnswerResult = 1 THEN 
         'Correct' 
       ELSE 'you have null value' 
       END 
    END 
 FROM t_AnswerSheet 
 WHERE UserId=@idparam", con);

Then again finally, pass the parameters to this command and execute it. Have a look here,
c# Using Parameters.AddWithValue in SqlDataAdapter - Stack Overflow[^]

Using these steps, you will be able to show the DataTable when there is data, otherwise show a message stating that the data is not found, instead of a blank DataTable.