C# 2008 object instance problem. Please help?

Question

So I am having a bit of a problem here with a class assignment I'm doing. Yes we have to use visual studio 2008. It's a payroll system that stores the employees name, pay rate, start date, and end date into a database. Now everything executes fine until I start inputting the information. It says "NullReferenceException was unhandled by user code" with the following description: "Object reference not set to an instance of an object".

Data layer code:
// This function saves the personnel data
    public static bool SavePersonnel(string Database, string FirstName, string LastName,
                                     string PayRate, string StartDate, string EndDate)
    {

bool recordSaved;

try
        {
            // Add your comments here
            OleDbConnection conn = new OleDbConnection("PROVIDER=Microsoft.Jet.OLEDB.4.0;" +
                                                       "Data Source=" + Database);
            conn.Open();
            OleDbCommand command = conn.CreateCommand();
            string strSQL;
            // Add your comments here
            strSQL = "Insert into tblPersonnel " +
                     "(FirstName, LastName, PayRate, StartDate, EndDate) values ('" +
                     FirstName + "', '" + LastName + "', " + PayRate + ", '" + StartDate +
                    "', '" + EndDate + "')";
            // Add your comments here
            command.CommandType = CommandType.Text;
            command.CommandText = strSQL;
            // Add your comments here
            command.ExecuteNonQuery();
            //closes connection
            conn.Close();
            recordSaved = true;
        }
        catch (Exception ex)
        {
            recordSaved = false;

}

return recordSaved;
    }

Here is the frmPersonnelVerified verifying code

// saving the personnel information
        if (clsDataLayer.SavePersonnel(Server.MapPath("PayrollSystem_DB.mdb"), 
            Session["txtFirstName"].ToString(),
         Session["txtLastName"].ToString(),
               Session["txtPayRate"].ToString(),
         Session["txtStartDate"].ToString(),
         Session["txtEndDate"].ToString()))
        {
            txtVerifiedInfo.Text = txtVerifiedInfo.Text +
                                  "&#92;nThe information was successfully saved!";

}
        else
        {
            txtVerifiedInfo.Text = txtVerifiedInfo.Text +
                                 "&#92;nThe information was NOT saved.";

}

Now when I click "continue" my webpage shows this line of code highlighted:

if (clsDataLayer.SavePersonnel(Server.MapPath("PayrollSystem_DB.mdb"),

Any tips? If you need more information I'll give more.

Anonymous · Accepted Answer

"Object reference not set" happens when a value is unexpectedly null. Of course you didn't tell us the line number (I guess you expect us to trace it out?). I'm not going to mentally compile and trace through your program for you. Set break points. Step through your code. Find the line it's failing on. Find the variable on that line that is null. Then find out why it's null. If you still cant figure it out tell us at least what line it fails on.

Ratchetr · Answer

Almost certainly, at least one of your Session["txtXXXX"] values is null. The exception will happen because of the ToString cal. (null.ToString() generates that exception).

Set a breakpoint on that line by clicking somewhere in that code, and hitting F9. There should be a red dot on left side of screen.

Run under debugger by hitting F5. Enter your data.

When you get the the breakpoint, Visual Studio should pop back up. If not, switch to it.

Highlight this part of your code: Session["txtFirstName"]. Right Click the highlighted text, and select QuickWatch. What does it show for the value of Session["txtFirstName"]? Is it null? If so, there is your problem. If not, repeat for all the other Session variables until you find that one that is null. Then figure out why it is null.

ETA: Are you putting these txtXXX values in Session state at some point? Or are they text controls on  your current page? If you are using Session state, then you need to figure out why that isn't happening. If they are text controls on your page, access the contents as txtXXXX.Text.

C# 2008 object instance problem. Please help?

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