getting error in Data access layer in N-tier architecture

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C#

public class empdata
    {
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["conn"].ToString());
}

hi wrote a code like this in DAL

  public class empdata
    {
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["conn"].ToString());
        
        
        
        
        public empdata()
        {
            
        }

        public empdata()
        {
            
        }

        public int Insertdata(empbo emb)
        {
            try
            {
                SqlCommand cmd = new SqlCommand("insertuser", con);
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@empid", emb.empid);
                cmd.Parameters.AddWithValue("@empname", emb.ename);
                cmd.Parameters.AddWithValue("@salary", emb.salary);
                cmd.Parameters.AddWithValue("@departmentid", emb.departmentid);
                int result = cmd.ExecuteNonQuery();
                cmd.Dispose();
                return result;

            }
            catch
            {
                throw;
            }
        }
}

i am getting an error

object reference not set to an instance of an object.<br />
<br />
Details System.NullReferenceException: Object reference not set to an instance of an object.<br />

plz help me to findout the solution.

thanq.

Posted 17-Jun-15 18:09pm

sreekanth12

Updated 17-Jun-15 18:32pm

Abhinav S

v3

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Sergey Alexandrovich Kryukov 18-Jun-15 0:27am

In what line?
—SA

sreekanth12 18-Jun-15 0:39am

it getting error at

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["conn"].ToString());

DamithSL 18-Jun-15 0:42am

do you have connection string with name conn in your web config file?

Sergey Alexandrovich Kryukov 18-Jun-15 9:59am

ConfigurationManager.ConnectionStrings["conn"] can be null...
I explained everything in my answer.
—SA

sreekanth12 18-Jun-15 0:48am

yes in app.config file

<add name="conn" connectionstring="server=****; Database=employee; Integrated Security=True" providername="System.Data.SqlClient">

DamithSL 18-Jun-15 0:59am

include the same connection string in the web.config file as well

sreekanth12 18-Jun-15 1:23am

ya got it bro thanq.

3 solutions

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Sergey Alexandrovich Kryukov · Answer 1 · 2015-06-17T18:27:00

You did not show where the exception with the message "Object reference not set to an instance of an object" is thrown.

Not to worry. This is one of the very easiest cases to detect and fix. It simply means that some member/variable of some reference type is dereferenced by using and of its instance (non-static) members, which requires this member/variable to be non-null, but in fact it appears to be null. Simply execute it under debugger, it will stop the execution where the exception is thrown. Put a break point on that line, restart the application and come to this point again. Evaluate all references involved in next line and see which one is null while it needs to be not null. After you figure this out, fix the code: either make sure the member/variable is properly initialized to a non-null reference, or check it for null and, in case of null, do something else.

Please see also: want to display next record on button click. but got an error in if condition of next record function "object reference not set to an instance of an object".

Sometimes, you cannot do it under debugger, by one or another reason. One really nasty case is when the problem is only manifested if software is built when debug information is not available. In this case, you have to use the harder way. First, you need to make sure that you never block propagation of exceptions by handling them silently (this is a crime of developers against themselves, yet very usual). The you need to catch absolutely all exceptions on the very top stack frame of each thread. You can do it if you handle the exceptions of the type System.Exception. In the handler, you need to log all the exception information, especially the System.Exception.StackTrace:
http://msdn.microsoft.com/en-us/library/system.exception.aspx,
http://msdn.microsoft.com/en-us/library/system.exception.stacktrace.aspx.

The stack trace is just a string showing the full path of exception propagation from the throw statement to the handler. By reading it, you can always find ends. For logging, it's the best (in most cases) to use the class System.Diagnostics.EventLog:
http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx.

Good luck,

—SA

Abhinav S · Answer 2 · 2015-06-17T18:23:00

Solution 1

Debug your code. Check where the error occurs.
Most likely, check the value in ConfigurationManager.ConnectionStrings["conn"] by using a watch.

Here is more on Using the Watch Window[^].

Posted 17-Jun-15 18:23pm

Abhinav S

sasanka sekhar panda · Answer 3 · 2015-06-17T18:34:00

C#

         SqlCommand cmd = new SqlCommand("insertuser", con);
           cmd.CommandType = CommandType.StoredProcedure;
           cmd.Parameters.AddWithValue("@empid", emb.empid);
           cmd.Parameters.AddWithValue("@empname", emb.ename);
           cmd.Parameters.AddWithValue("@salary", emb.salary);
           cmd.Parameters.AddWithValue("@departmentid", emb.departmentid);
            //corrected code
           con.Open();
           int result = cmd.ExecuteNonQuery();
           con.Close();
           cmd.Dispose();
           return result;
//If its not working then check your connection string in the web config file

getting error in Data access layer in N-tier architecture

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