"Object Reference not set to Instance of an object", please see the code below.

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This is the actual code and in this I am taking the values of the datagrid and sending it to the db through a sql stored proc, all the help appreciated. Please let me know if anything wrong in this that is causing the error

Private Sub BtnSendToGP_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnSendToGP.Click
 
        Dim VarItemNumber As String
         Dim VarItemDescription As String
         Dim VarUnitOfMeasure As String
         Dim VarItemClass As String
         Dim VarCurrentCost As String
         Dim Conn As SqlConnection
 

        Conn = New SqlConnection("Server = db02; Initial Catalog=SDPRD; User=xx; Password=xxxx" & "Data Source=Dynamics;Integrated Security=SSPI;")
         Try
             For cn As Integer = 0 To DtGridView.RowCount - 1
                 VarItemNumber = DtGridView(0, cn).Value.ToString
                 VarItemDescription = DtGridView(3, cn).Value.ToString
                 VarUnitOfMeasure = DtGridView(4, cn).Value.ToString
                 VarItemClass = DtGridView(5, cn).Value.ToString
                 VarCurrentCost = DtGridView(6, cn).Value.ToString
 
                Dim myCommand As SqlCommand = New SqlCommand("dbo.taUpdateCreateItemRcd", Conn)
                 If Conn.State = ConnectionState.Open Then Conn.Close()
                 Conn.Open()
                 myCommand.CommandType = Data.CommandType.StoredProcedure
                 myCommand.Parameters.AddWithValue("@I_vITEMNMBR", VarItemNumber)
                 myCommand.Parameters.AddWithValue("@I_vUseItemClass", 1)
                 myCommand.Parameters.AddWithValue("@I_vITEMDESC", VarItemDescription)
                 myCommand.Parameters.AddWithValue("@I_vUOMSCHDL", VarUnitOfMeasure)
                 myCommand.Parameters.AddWithValue("@I_vITMCLSCD", VarItemClass)
                 myCommand.Parameters.AddWithValue("@I_vCURRCOST", VarCurrentCost)
                 myCommand.Parameters.AddWithValue("@O_iErrorState", 0)
                 myCommand.Parameters.AddWithValue("@oErrString", 0)
                 myCommand.ExecuteNonQuery()
             Next
         Catch ex As Exception
             MsgBox(ex.ToString)
         Finally
             If Conn.State = ConnectionState.Open Then
                 Conn.Close()
             End If
         End Try
         MsgBox("All The Records Added To GP Successfully...", MsgBoxStyle.Information)
     End Sub

Posted 30-Apr-13 8:59am

FARMAN786

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Comments

Richard C Bishop 30-Apr-13 15:02pm

Well that error means you are trying to use an object that has not been instantiated. Debug the code and figure out which line it is.

[no name] 30-Apr-13 15:04pm

Of course something is wrong, otherwise you would not be getting an error. What you failed to do was debug your code and find the line that was throwing the error. If you have done that, you would have found the object that you was trying to use that was null. Then you would have been able to fix it. Since there are several things that could be causing the error, I will not be making any guesses.

FARMAN786 30-Apr-13 15:06pm

how do i debug a .dll, any ideas.

Thanks,

[no name] 30-Apr-13 16:35pm

The exact same way you debug anything else. Place a break point in the code and run it.

3 solutions

Solution 2

There should be more in the stack trace.

Based on above code, most susceptible lines are:

C#

VarItemNumber = DtGridView(0, cn).Value.ToString
VarItemDescription = DtGridView(3, cn).Value.ToString
VarUnitOfMeasure = DtGridView(4, cn).Value.ToString
VarItemClass = DtGridView(5, cn).Value.ToString
VarCurrentCost = DtGridView(6, cn).Value.ToString

Object reference not set to an instance of an object: This error happens when you try to use a property or call a method of an object that is null. More details: here[^]

A simple use of Visual studio DEBUGGER can tell you the object because of which it is happening. Just look at the stack trace and put a debugger on that line. Check the objects of that line and see if any one is null and you are trying to use that objects property. Handle the same.

BTW, why there are no brackets after ToString in any of the code lines above, like x.ToString(), Refer: MSDN: Object.ToString Method [^]

Posted 30-Apr-13 9:46am

Sandeep Mewara

Updated 30-Apr-13 9:48am

v2

Comments

FARMAN786 30-Apr-13 17:19pm

Thanks, I will check that but is there any other mthod to code the above line in order to grab the data from the grid and feed it to the stored proc

Solution 3

Hi Sergey,

We can get rid of the last column by using the syntax below.

DtGridView.AllowUserToAddRows = False

Thanks a lot for all your help.

Posted 30-Apr-13 14:32pm

FARMAN786

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

Sergey Alexandrovich Kryukov · Accepted Answer · 2013-04-30T09:41:00

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

"Object Reference not set to Instance of an object", please see the code below.

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"Object Reference not set to Instance of an object", please see the code below.

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