How to validate whether the student id is exists in database or nor

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Note it is web application.

Validating the student id is exists in database or not for that code as follows;

C#

SCon.Con.Open();
  string str = "Select  count(*)  from Studdet where studid = " + txt_Studid.Text.ToString() + "";
  SqlCommand cmd = new SqlCommand(str, SCon.Con);
  cmd.Parameters.AddWithValue("studid", txt_Studid.Text);
   int count = cmd.ExecuteScalar();
         if (count > 0)
        {
            Label4.Text = "Correct Student id";
            return;
        }
        else
        {
            Label4.Text = "InCorrect student id is there";
            return;
        }
           SCon.Con.Close();

in the run mode i enter the student id in the txt_Studid(textbox) and click the show button error as follows;

Cannot implicitly convert type 'object' to 'int'. An explicit conversion exists (are you missing a cast?

what is the problem in my code. please help me.

Regards,
Narasiman P.

Posted 30-Apr-13 23:27pm

Member 8054539

Updated 1-May-13 0:21am

Pheonyx

v2

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Pheonyx · Answer 1 · 2013-05-01T00:25:00

Assuming the actual SQL statement you are trying to run is correct I would change your code as follows:

C#

SCon.Con.Open();
  string str = "Select  count(*)  from Studdet where studid = @studid";
  SqlCommand cmd = new SqlCommand(str, SCon.Con);
  cmd.Parameters.AddWithValue("@studid", Convert.ToInt(txt_Studid.Text.Trim()));

This is:
a) uses parameters to reduce changes of SQL injection,
b) allows the SQL query to actually work with the given parameter.
c) Converts the text entered to an integer value

I would also add additional checking on the information entered into the txt_Studid text box using the validating event to ensure only positive integer values have been entered but that is addition.

I would also do the following as suggested by nitin bhoyate in his solution.

C#

int count =0;
object obj = cmd.ExecuteScalar();
if(obj!=null)
{
count =convert.toint(obj.tostring());

}

Simon_Whale · Answer 2 · 2013-05-01T00:08:00

Solution 2

You haven't set up your parameters correctly have a read of this
http://stackoverflow.com/questions/2701506/sql-inline-query-with-parameters-parameter-is-not-read-when-the-query-is-execut[^].

Answer 1 will give you a good example on how to do this.

Posted 1-May-13 0:08am

Simon_Whale

Hitesh Gohel · Answer 3 · 2013-05-01T00:10:00

Hello,
You Just Add this code as below you problem is solve.

C#

string str = "Select count(*) from Studdet where studid = " + txt_Studid.Text.ToString() + "";
            SqlCommand cmd = new SqlCommand(str, cn);
            cn.Open();
            int count = 0;
            object obj = cmd.ExecuteScalar();
            count = Convert.ToInt32(obj);
            if (count > 0)
            {
                Label4.Text = "Correct Student id";
                return;
            }
            else
            {
                Label4.Text = "InCorrect student id is there";
                return;
            }
            cn.Close();

vaishali thaker · Answer 4 · 2013-05-01T00:30:00

Why dont u try this...

SCon.Con.Open();
string str = "Select count(*) from Studdet where studid = " + txt_Studid.Text.ToString();
SqlCommand cmd = new SqlCommand(str, SCon.Con);
cmd.Parameters.AddWithValue("studid", Convert.ToInt32(txt_Studid.Text));
int count = cmd.ExecuteScalar();
if (count > 0)
{
Label4.Text = "Correct Student id";
return;
}
else
{
Label4.Text = "InCorrect student id is there";
return;
}
SCon.Con.Close();

nitin bhoyate · Answer 5 · 2013-04-30T23:29:00

instrad of this

C#

string str = "Select count(*) from Studdet where studid = " + txt_Studid.Text.ToString() + "";

Use

C#

string str = "Select count(*) from Studdet where studid = '" + txt_Studid.Text.ToString() + "'";

also remove

C#

cmd.Parameters.AddWithValue("studid", txt_Studid.Text);

also replace

C#

int count = cmd.ExecuteScalar();

by

C#

int count =0;
object obj = cmd.ExecuteScalar();
if(obj!=null)
{
count =convert.toint(obj.tostring());

}

here you are not using any parameter to pass the value you are passing direct value to the query.
this will solve problem

How to validate whether the student id is exists in database or nor

5 solutions

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